U.S. patent application number 11/219216 was filed with the patent office on 2006-01-19 for point of care diagnostic systems.
Invention is credited to Emory V. Anderson, Duane Desieno, Robert Hussa, Lynn Jones, Jerome P. Lapointe, Ricardo R. Martinez, Gail Marzolf, Edward Nemec, Ronald Pong, Andrew Senyei.
Application Number | 20060014302 11/219216 |
Document ID | / |
Family ID | 26690482 |
Filed Date | 2006-01-19 |
United States Patent
Application |
20060014302 |
Kind Code |
A1 |
Martinez; Ricardo R. ; et
al. |
January 19, 2006 |
Point of care diagnostic systems
Abstract
Systems and methods for medical diagnosis or risk assessment for
a patient are provided. These systems and methods are designed to
be employed at the point of care, such as in emergency rooms and
operating rooms, or in any situation in which a rapid and accurate
result is desired. The systems and methods process patient data,
particularly data from point of care diagnostic tests or assays,
including immunoassays, electrocardiograms, X-rays and other such
tests, and provide an indication of a medical condition or risk or
absence thereof. The systems include an instrument for reading or
evaluating the test data and software for converting the data into
diagnostic or risk assessment information.
Inventors: |
Martinez; Ricardo R.; (San
Antonio, TX) ; Marzolf; Gail; (Cupertino, CA)
; Pong; Ronald; (San Jose, CA) ; Jones; Lynn;
(Mountainview, CA) ; Hussa; Robert; (Sunnyvale,
CA) ; Senyei; Andrew; (La Jolla, CA) ;
Anderson; Emory V.; (Danville, CA) ; Nemec;
Edward; (Duluth, GA) ; Lapointe; Jerome P.;
(Oakland, CA) ; Desieno; Duane; (La Jolla,
CA) |
Correspondence
Address: |
FISH & RICHARDSON, PC
P.O. BOX 1022
MINNEAPOLIS
MN
55440-1022
US
|
Family ID: |
26690482 |
Appl. No.: |
11/219216 |
Filed: |
September 2, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10877122 |
Jun 25, 2004 |
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11219216 |
Sep 2, 2005 |
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|
09717478 |
Nov 20, 2000 |
6867051 |
|
|
10877122 |
Jun 25, 2004 |
|
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|
09063497 |
Apr 20, 1998 |
6394952 |
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09717478 |
Nov 20, 2000 |
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09017901 |
Feb 3, 1998 |
6267722 |
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09717478 |
Nov 20, 2000 |
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Current U.S.
Class: |
436/518 ;
435/287.2; 702/19 |
Current CPC
Class: |
G16H 10/40 20180101;
Y10S 436/811 20130101; G01N 21/474 20130101; G16H 50/20 20180101;
G16H 30/40 20180101; G01N 2333/78 20130101; G01N 33/689 20130101;
Y02A 90/10 20180101; G01N 21/8483 20130101; G16H 10/60 20180101;
G01N 33/558 20130101; G01N 33/6887 20130101; Y10S 436/814 20130101;
G16H 15/00 20180101; G01N 2800/368 20130101 |
Class at
Publication: |
436/518 ;
702/019; 435/287.2 |
International
Class: |
G01N 33/48 20060101
G01N033/48; C12M 1/34 20060101 C12M001/34; G01N 33/543 20060101
G01N033/543 |
Claims
1. A method for determining results from an immunoassay,
comprising: (a) testing a patient sample for the presence of a
target analyte indicative of a condition or risk of having the
condition by reacting the sample with antibodies specific for the
analyte in a sandwich assay performed on a test strip, in which one
of the antibodies is labeled with a detectable label; and (b)
detecting a reflectance signal produced by the label in a
reflectance reader, wherein: the reflectance reader includes a
reader head that comprises: (i) a reader head body; (ii) a light
emitting diode (LED); (iii) a first fiberoptic bundle optically
coupled to the light emitting diode; (iv) a photodetector; (v) a
second fiberoptic bundle optically coupled to the photodetector;
and (vi) an aperture in the reader head body, wherein fiberoptic
conductor ends of the first fiberoptic bundle and fiberoptic
conductor ends of the second fiberoptic bundle are arranged in a
substantially co-planar relationship to form a planar surface, and
the planar surface is substantially parallel to a plane at an upper
surface of the test strip during reflectance signal detection,
whereby light is conducted by fiberoptic bundles to the
photodetector, which generates the reflectance signal indicative of
an amount of reflected light; and the reflectance signal is
indicative of the presence of the analyte.
2. The method of claim 1, wherein the fiberoptic conductor ends of
the first fiberoptic bundle and the fiberoptic conductor ends of
the second fiberoptic bundle are arranged in a sigmoidal
distribution in the aperture.
3. The method of claim 1, wherein the reader head further comprises
a third fiberoptic bundle optically connected to a second light
emitting diode, wherein fiberoptic conductor ends of the third
fiberoptic bundle are arranged in a substantially coplanar
relationship with the fiberoptic conductor ends of the first
fiberoptic bundle and the fiberoptic conductor ends of the second
fiberoptic bundle.
4. The method of claim 3, wherein the fiberoptic conductor ends of
the first fiberoptic bundle and the fiberoptic conductor ends of
the second fiberoptic bundle and the fiberoptic conductor ends of
the third fiberoptic bundle are arranged in a sigmoidal
distribution in the aperture.
5. The method of claim 1, wherein the target analyte is fetal
fibronectin.
Description
RELATED APPLICATIONS
[0001] This application is divisional of U.S. application Ser. No.
10/877,122 to Emory V. Anderson, Edward Nemec, Jerome Lapointe,
Duane DeSieno, Ricardo Martinez, Gail Marzolf, Ronald Pong, Lynn
Jones, Robert O. Hussa and Andrew Senyei, entitled "POINT OF CARE
DIAGNOSTIC SYSTEMS," filed Jun. 25, 2004, which is a continuation
of U.S. application Ser. No. 09/717,478 to Emory V. Anderson,
Edward Nemec, Jerome Lapointe, Duane DeSieno, Ricardo Martinez,
Gail Marzolf, Ronald Pong, Lynn Jones, Robert O. Hussa and Andrew
Senyei, entitled "POINT OF CARE DIAGNOSTIC SYSTEMS," filed Nov. 20,
2000, which is a divisional of U.S. application Ser. No.
09/063,497, filed Apr. 20, 1998, and now U.S. Pat. No. 6,394,952,
and a continuation-in-part of U.S. application Ser. No. 09/017,901,
now U.S. Pat. No. 6,267,722, filed Feb. 3, 1998 to Emory V.
Anderson, Edward Nemec, Jerome Lapointe, Duane DeSieno, Ricardo
Martinez, Gail Marzolf, Ronald Pong, Lynn Jones, Robert O. Hussa
and Andrew Senyei, entitled "POINT OF CARE DIAGNOSTIC SYSTEMS."
Priority under 35 U.S.C. '120 is claimed to these applications.
[0002] This application also is related to abandoned U.S.
application Ser. No. 08/599,275 to Jerome Lapointe and Duane
DeSieno, filed Feb. 9, 1996, entitled "METHOD FOR DEVELOPING
MEDICAL AND BIOCHEMICAL DIAGNOSTIC TESTS USING NEURAL NETWORKS,"
abandoned U.S. application Ser. No. 08/798,306 to Jerome Lapointe
and Duane DeSieno, filed Feb. 7, 1997, entitled "METHOD FOR
SELECTING MEDICAL AND BIOCHEMICAL DIAGNOSTIC TESTS USING NEURAL
NETWORK-RELATED APPLICATIONS," and U.S. application Ser. No.
08/912,133, now U.S. Pat. No. 6,678,669, to Jerome Lapointe and
Duane DeSieno, filed Aug. 14, 1997, entitled "METHOD FOR SELECTING
MEDICAL AND BIOCHEMICAL DIAGNOSTIC TESTS USING NEURAL
NETWORK-RELATED APPLICATIONS." This application also is related to
U.S. Pat. Nos. 5,096,830, 5,185,270, 5,223,440, 5,236,846,
5,281,522, 5,468,619 and 5,516,702.
[0003] The subject matter of each of these patents and each of U.S.
application Ser. Nos. 10/877,122, 09/717,478, 09/017,901,
08/599,275, 08/798,306 and 08/912,133 is herein incorporated herein
by reference in its entirety. The subject matter of published
International PCT application No. WO 97/29447, which corresponds to
U.S. application Ser. No. 08/912,133 also is herein incorporated in
its entirety by reference thereto. Also incorporated by reference
are design patent patents D434,153 and D432,244, based on design
applications 29/086,781 and 29/086,799, respectively, each filed
Apr. 20, 1998.
FIELD OF THE INVENTION
[0004] The present invention relates to systems and methods that
aid in providing a medical diagnosis or risk assessment for a
patient using biochemical and historic patient data, including data
from point of care diagnostic tests or assays, and processing the
information to give an indication of a medical condition or
risk.
BACKGROUND
[0005] Evaluation of Immunoassay Data
[0006] In diagnostic immunochromatographic assays, where results
are determined by a color change or the production of color,
results are generally detected visually by human eye. As a result
of the human perception and judgment involved, there is significant
variance among those interpreting such test results as to whether a
color change or other measurable signal has occurred, and the
degree of such occurrence. Furthermore, there is a great deal of
subjectivity involved in interpreting whether immunoassay results
are positive or negative. This is particularly pronounced where the
result is close to a threshold value. The variance is further
enhanced when attempts are made to quantitate such assay test
results. Accurate results may be critical for certain diagnostic
assays.
[0007] It is desirable to develop techniques that are objective in
nature, and that reduce the error associated with interpreting
immunochromatographic and other assay test results. Therefore, it
is an object herein to provide systems, methods, devices and
instruments for objectively assessing data from biochemical and
other tests and to use such data for diagnosis and risk assessment.
It also is an object herein to incorporate decision-support
methodologies into such systems and thereby enhance the diagnostic
and risk assessment capabilities thereof.
[0008] It also is an object herein to provide systems and methods
for use in detecting and measuring fetal fibronectin (fFN) levels
in a patient sample and using such information to diagnose and
assess risks of preterm labor, fetal membrane rupture and other
related disorders and conditions.
SUMMARY
[0009] Systems and methods for medical diagnosis or risk assessment
for a patient are provided. These systems and methods are designed
to be employed at the point of care, such as in emergency rooms,
operating rooms, hospital laboratories and other clinical
laboratories, doctor's offices, in the field, or in any situation
in which a rapid and accurate result is desired. The systems and
methods process patient data, particularly data from point of care
diagnostic tests or assays, including immunoassays, chemical
assays, nucleic acid assays, calorimetric assays, fluorometric
assays, chemiluminescent and bioluminescent assays,
electrocardiograms, X-rays and other such tests, and provide an
indication of a medical condition or risk or absence thereof.
[0010] The systems include an instrument for reading or evaluating
the test data and software for converting the data into diagnostic
or risk assessment information. In certain embodiments, the systems
include a test device, such as a test strip, optionally encased in
a housing, for analyzing patient samples and obtaining patient
data. In particular embodiments, the device includes a symbology,
such as a bar code, which is used to associate identifying
information, such as intensity value, standard curves, patient
information, reagent information and other such information, with
the test device. The reader in the system is optionally adapted to
read the symbology.
[0011] Further, the systems optionally include a decision-support
system or systems, such as a neural network, for evaluating the
digitized data, and also for subsequent assessment of the data,
such as by integration with other patient information, including
documents and information in medical records. All software and
instrument components are preferably included in a single package.
Alternatively, the software can be contained in a remote computer
so that the test data obtained at a point of care can be sent
electronically to a processing center for evaluation. Thus, the
systems operate on site at the point of care, such as in a doctor's
office, or remote therefrom.
[0012] The patient information includes data from physical and
biochemical tests, such as immunoassays, and from other procedures.
The test is performed on a patient at the point of care and
generates data that can be digitized, such as by an electronic
reflectance or transmission reader, which generates a data signal.
The signal is processed using software employing data reduction and
curve fitting algorithms, or a decision support system, such as a
trained neural network, or combinations thereof, for converting the
signal into data, which is used to aid in diagnosis of a medical
condition or determination of a risk of disease. This result may be
further entered into a second decision support system, such as a
neural net, for refinement or enhancement of the assessment.
[0013] In a particular embodiment, systems and methods for
detecting and measuring levels of a target analyte in a patient
sample, analyzing the resulting data, and providing a diagnosis or
risk assessment are provided. The systems and methods include an
assay device in combination with a reader, particularly a
computer-assisted reader, preferably a reflectance reader, and data
processing software employing data reduction and curve fitting
algorithms, optionally in combination with a trained neural network
for accurately determining the presence or concentration of analyte
in a biological sample. The methods include the steps of performing
an assay on a patient sample, reading the data using a reflectance
reader and processing the reflectance data using data processing
software employing data reduction algorithms. In a particular
embodiment, the assay is an immunoassay. Preferred software
includes curve fitting algorithms, optionally in combination with a
trained neural network, to determine the presence or amount of
analyte in a given sample. The data obtained from the reader then
can be further processed by the medical diagnosis system to provide
a risk assessment or diagnosis of a medical condition as output. In
alternative embodiments, the output can be used as input into a
subsequent decision support system, such as a neural network, that
is trained to evaluate such data.
[0014] In a preferred embodiment, the assay device is a lateral
flow test strip, preferably, though not necessarily, encased in a
housing, designed to be read by the reader, and the assay is a
sandwich immunoassay. For example, in one embodiment thereof, a
patient sample is contacted with an antibody for a selected target
analyte indicative of a disease, disorder or risk thereof. The
antibody is preferably labeled by conjugation to a physically
detectable label, and upon contacting with the sample containing
the target analyte forms a complex. The antibody-analyte complex is
then contacted with a second antibody for the antigen, which is
immobilized on a solid support. The second antibody captures the
antibody-analyte complex to form an antibody-analyte-antibody
sandwich complex, and the resulting complex, which is immobilized
on the solid support, is detectable by virtue of the label. The
test strip is then inserted into a reader, where the signal from
the label in the complex is measured. Alternatively, the test strip
could be inserted into the reader prior to addition of the sample.
Additionally, the housing may include a symbology, such as a bar
code, which also is read by the reader and contains data related to
the assay device and/or test run. The signal obtained is processed
using data processing software employing data reduction and curve
fitting algorithms, optionally in combination with a trained neural
network, to give either a positive or negative result, or a
quantitative determination of the concentration of analyte in the
sample, which is correlated with a result indicative of a risk or
presence of a disease or disorder. This result can optionally be
input into a decision support system, and processed to provide an
enhanced assessment of the risk of a medical condition as output.
The entire procedure may be automated and/or
computer-controlled.
[0015] In certain embodiments, the reflectance reader is adapted to
read a symbology on the test device. The symbology is preferably a
bar code, which can be read in the same manner that the test strip
in the device can be read. In these embodiments, the reader head
scans across a bar code in a stepwise fashion. The data collected
from the bar code is transformed into integrated peak information
and analyzed as alphanumeric characters, which are related to
information related to the particular device and/or test run or
other information, including patient information. Any bar code from
among the many known in the industry can be employed. In preferred
embodiments, Code 39 (a trademark of Interface Mechanism, Inc.,
Lynnwood, Wash.; see, e.g., U.S. Pat. No. 4,379,224, U.S. Pat. No.
4,438,327, U.S. Pat. No. 4,511,259 or Code 128 bar codes (see,
e.g., U.S. Pat. No. 5,227,893) are used.
[0016] In a particular embodiment, the analyte to be detected is
fetal fibronectin (fFN) and the result obtained is a positive or
negative indication of pregnancy or the risk of certain
pregnancy-related conditions or fertility and infertility-related
conditions, including ectopic pregnancy, preterm labor,
pre-eclampsia, imminent delivery, term induction and fetal membrane
rupture. Thus, provided herein is a rapid fFN test using a lateral
flow test device. At the very least, this test provides the same
clinically relevant information as a fFN ELISA (an enzyme linked
immunosorbent sandwich assay (ELISA)) test heretofore available in
significantly less time and at the point of care. The fFN
immunoassay provided herein allows the user to test a
cervicovaginal swab sample in about 20 minutes. When practiced as
described herein, additional information, such as a more accurate
risk assessment or diagnosis, can be obtained.
[0017] The system herein provides a means to detect and to
quantitate concentrations of fFN throughout pregnancy and to assess
the risk and detect conditions associated therewith. Because of the
sensitivity of the combination of the reader and devices provided
herein, fFN may be monitored throughout pregnancy, including times
when it is not detected by less sensitive systems.
[0018] The reflectance reader and test strip device also are
provided herein. Also provided herein are the neural nets for
assessing the data.
[0019] A method for classifying an image also is provided. The
method includes the steps of reducing the image to a set of derived
parameters from which the image can be reconstructed within a
predetermined degree of tolerance; inputting the derived parameters
into a classification neural network; and determining the
classification of the image based on the output of the
classification neural network. The method of reducing the image to
a set of derived parameters is achieved by defining a mathematical
function that contains a plurality of parameters representative of
the image; and optimizing the parameters of the function using a
methodology that minimizes the error between the image and a
reconstruction of the image using the function.
[0020] In an alternative embodiment, the method of reducing the
image to a set of derived parameters is achieved by inputting the
image into a trained neural network, where the inputs to the
network represent the image, the hidden layer of the network is
such that the number of hidden elements is smaller than the number
of inputs to the network, and the outputs of the network represent
reconstruction of the image; and setting the derived parameters to
the output values of the trained neural network.
[0021] In another alternative embodiment, the method of reducing
the image to a set of derived parameters is achieved by defining a
neural network in which the inputs to the network are the
coordinates of a point in the image, the hidden layer contains a
plurality of elements, and the output of the network represents the
reconstruction of the associated point in the image; training the
neural network so that the error between the network output and the
image are minimized for all points in the image; and setting the
derived parameters to the weights of the hidden layer of the
trained neural network.
[0022] The neural networks and computer systems used in the methods
also are provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1A is a top view of an assay test strip, such as an
immunoassay test strip;
[0024] FIG. 1B is a side view of the assay test strip of FIG.
1;
[0025] FIG. 2A is a perspective view of an assay device, including
the assay test strip of FIG. 1A and FIG. 1B and housing assembly
and showing a bar code, which can optionally be affixed to the
housing;
[0026] FIG. 2B is a perspective view of an alternative embodiment
of an assay device, including the assay test strip of FIG. 1A and
FIG. 1B and housing assembly and showing a bar code, which can
optionally be affixed to the housing;
[0027] FIG. 3 is a perspective view of the assay device of FIG. 2B
showing the individual components of the device;
[0028] FIG. 4 is a top view of an exemplary housing assembly for
the assay test strip of FIG. 1;
[0029] FIG. 5 is a side assembly view of the housing assembly of
FIG. 4;
[0030] FIG. 6 is a top view of an embodiment of an assay reader and
an assay device, inserted therein, in accordance with an exemplary
embodiment of the reader;
[0031] FIG. 7 is a perspective view of portion of the assay device
of FIG. 2A shown inserted into a cassette slot of a lower housing
and extending to a reader head assembly within an exemplary
embodiment of an assay reader;
[0032] FIG. 8 is a top view of the lower housing of the assay
reader of FIG. 7 with the assay device inserted therein and a
stepper motor shown positioned relative to the assay device as is
when the assay device is fully inserted into the cassette slot of
the reader;
[0033] FIG. 9 is a side view of the lower housing of the reader
device of FIG. 7 with the assay device of FIG. 2A fully inserted
with the stepper motor shown positioned relative to the fully
inserted assay device, with a reader head shown positioned in a
lowered position over a test opening of the assay device, and with
a carriage wheel shown engaged by the assay device so as to lower
the reader head into its lowered position therein;
[0034] FIG. 10 is a side view of a reader head assembly such as is
found in the reader device of FIG. 6;
[0035] FIG. 11 is a side view of a reader head of the reader head
assembly of FIG. 10;
[0036] FIG. 12 is a reverse angle side view of the reader head
assembly of FIG. 10;
[0037] FIG. 13 is a reverse angle side view of the reader head of
FIG. 11;
[0038] FIG. 14 is a side view of the reader head assembly of FIG.
10, having been actuated so as to pivot the reader head assembly
into a raised position suitable for insertion and removal of the
assay device into and from the reader head assembly within the
assay reader;
[0039] FIG. 15 is an end view of the reader head of FIG. 11;
[0040] FIG. 16 is an end view of the reader head assembly of FIG.
10;
[0041] FIG. 17 is a cut-away view of the reader head assembly of
FIG. 11 with first and second light emitting diodes, a
photodetector, corresponding fiberoptic bundles and an aperture at
a lower end thereof depicted;
[0042] FIG. 18 is a partial closeup cross-sectional view of a
reader head tip of the reader head of FIG. 17 showing the aperture
and ends of fiberoptic fibers of the fiberoptic bundles of FIG.
17;
[0043] FIG. 19 is a closeup bottom view of the aperture of the
reader head of FIGS. 17 and 18 illustrating a sigmoidal pattern for
positioning individual fiberoptic fibers (fiberoptic
conductors);
[0044] FIG. 20 is a closeup end view of the corresponding
fiberoptic bundle at the first light emitting diode of FIG. 17 from
which the fiberoptic bundle conducts light from the first light
emitting diode;
[0045] FIG. 21 is a schematic diagram illustrating a process by
which an assay test strip is analyzed so as to determine an amount
of background light at a control region of the assay test
strip;
[0046] FIG. 22 is a schematic diagram illustrating a process by
which an assay test strip is analyzed so as to determine an amount
of reflection resulting from a first illumination of a control
portion of the assay test strip; and
[0047] FIG. 23 is a schematic view diagram illustrating a process
by which an assay test strip is analyzed so as to determine an
amount of reflection resulting from a second illumination of a
control portion of the assay test strip;
[0048] FIG. 24 is a side view of an exemplary embodiment of the
reader that is adapted for reading a bar code; and
[0049] FIG. 25 is an example of a bar code in accordance with an
exemplary embodiment of the assay device.
DETAILED DESCRIPTION
Definitions
[0050] Unless defined otherwise, all technical and scientific terms
used herein have the same meaning as is commonly understood by one
of skill in the art to which this invention belongs. All patents
and publications referred to herein are, unless noted otherwise,
incorporated by reference in their entirety. In the event a
definition in this section is not consistent with definitions
elsewhere, the definition set forth in this section will
control.
[0051] As used herein, point of care testing refers to real time
diagnostic testing that can be done in a rapid time frame so that
the resulting test is performed faster than comparable tests that
do not employ this system. For example, the exemplified fFN
immunoassay, is performed in less time than the fFN ELISA assay
(i.e., less than about 3 to 4 hours, preferably less than 1 hour,
more preferably less than half an hour). In addition, with the
method and devices provided herein, it can be performed rapidly and
on site, such as in a doctor's office, at a bedside, in a stat
laboratory, emergency room or other such locales, particularly
where rapid and accurate results are required. The patient can be
present, but such presence is not required. Point of care includes,
but is not limited to: emergency rooms, operating rooms, hospital
laboratories and other clinical laboratories, doctor's offices, in
the field, or in any situation in which a rapid and accurate result
is desired.
[0052] As used herein, an anti-fFN antibody is an antibody that
binds selectively with fFN. Such antibodies are known to those of
skill in the art and also may be readily isolated.
[0053] As used herein, a test strip refers to any means on which
patient test data or other data is generated, recorded or displayed
in a manner that forms an image or from which an image can be
generated. Such strips, include, but are not limited to,
immunochromatographic test strips, such as lateral flow devices,
X-ray films, such as X-rays and films produced from sequencing
gels, EKG printouts, MRI results and other such means that generate
or from which an image as defined herein can be generated. The
strip is preferably adapted for scanning or reading by a reader,
preferably the reader provided herein. Although referred to as a
"strip," it can be of any shape or geometry, including rectangular,
three dimensional, circular, and so forth.
[0054] As used herein, a sigmoidal pattern (also referred to herein
as sigmoidal-like; see, e.g., FIG. 19) with reference to the
fiberoptics refers to the S-shaped or snake-like pattern of
illumination selected for maximizing illumination across the lines
on the test strip. The pattern is not strictly a sigmoidal shape,
but refers to a pattern such as that depicted in FIG. 19, which
pattern provides a means for adding more area to any reading. Any
other pattern that achieved this result is encompassed within this
expression.
[0055] As used herein, quantitative results are results that are
absolute or relative values; qualitative results are typically
negative or positive type results.
[0056] As used herein, fetal restricted antigens refers to antigen
that are present in pregnant women uniquely, or in substantially
elevated amounts compared to non-pregnant women in maternal serum,
plasma, urine, saliva, sweat, tears and other bodily fluids.
[0057] As used herein, fetal fibronectin is a fetal restricted
antigen found in placenta, amniotic fluid and fetal connective
tissue. It differs structurally from adult fibronectins. Fetal
fibronectin is not present in significant quantities in maternal
plasma or serum. Fetal fibronectin may be captured with a general
binding antibody, such as an anti-fibronectin antibody, or an
anti-fetal restricted antigen antibody, such as anti-fetal
fibronectin antibody.
[0058] As used herein, an immunoassay is defined as any method
using a preferential binding of an antigen with a second material,
a binding partner, usually an antibody or another substance having
an antigen binding site, which binds preferentially with an epitope
of the fetal restricted antigen. Preferential binding, as used
herein, refers to binding between binding partners that is
selective and generally specific, and demonstrates less than 10%,
preferably less than 5%, cross-reactive nonspecific binding. The
immunoassay methods provided herein include any known to those of
skill in the art, including, but not limited to, sandwich,
competition, agglutination or precipitation, for example.
[0059] As used herein, a solid support refers to the material to
which the antibody is linked. A variety of materials can be used as
the solid support. The support materials include any material that
can act as a support for attachment of the molecules of interest.
Such materials are known to those of skill in this art. These
materials include, but are not limited to, organic or inorganic
polymers, natural and synthetic polymers, including, but not
limited to, agarose, cellulose, nitrocellulose, cellulose acetate,
other cellulose derivatives, dextran, dextran-derivatives and
dextran copolymers, other polysaccharides, glass, silica gels,
gelatin, polyvinyl pyrrolidone, rayon, nylon, polyethylene,
polypropylene, polybutlyene, polycarbonate, polyesters, polyamides,
vinyl polymers, polyvinylalcohols, polystyrene and polystyrene
copolymers, polystyrene cross-linked with divinylbenzene or the
like, acrylic resins, acrylates and acrylic acids, acrylamides,
polyacrylamides, polyacrylamide blends, copolymers of vinyl and
acrylamide, methacrylates, methacrylate derivatives and copolymers,
other polymers and co-polymers with various functional groups,
latex, butyl rubber and other synthetic rubbers, silicon, glass,
paper, natural sponges, insoluble protein, surfactants, red blood
cells, metals, metalloids, magnetic materials, or other
commercially available media.
[0060] As used herein, a reader refers to an instrument for
detecting and/or quantitating data, such as on test strips. The
data may be visible to the naked eye, but does not need to be
visible.
[0061] As used herein, a reflectance reader refers to an instrument
adapted to read a test strip using reflected light, including
fluorescence, or electromagnetic radiation of any wavelength.
Reflectance can be detected using a photodetector or other
detector, such as charge coupled diodes (CCD). A preferred
reflectance reader, which is provided and described herein,
includes a cassette slot adapted to receive a test-strip,
light-emitting diodes, optical fibers, a sensing head, including
means for positioning the sensing head along the test strip, a
control circuit to read the photodetector output and control the on
and off operation of the light-emitting diodes, a memory circuit
for storing raw and/or processed data, and a photodetector, such as
a silicon photodiode detector.
[0062] As used herein, a sensing head refers to the assembly which
is adapted to read a test strip using reflected light or other
electromagnetic radiation. Thus, the sensing head in the reader
provided herein refers to the part of the sensing head assembly
that randomizes the optical bundles and arranges the fibers in the
plane normal to the test strip.
[0063] As used herein, color refers to the relative energy
distribution of electromagnetic radiation within the visible
spectrum. Color can be assessed visually or by using equipment,
such as a photosensitive detector.
[0064] As used herein, a color change refers to a change in
intensity or hue of color or may be the appearance of color where
no color existed or the disappearance of color.
[0065] As used herein, a decision-support system, also referred to
as a "data mining system" or a "knowledge discovery in data
system", is any system, typically a computer-based system, that can
be trained on data to classify the input data and then subsequently
used with new input data to make decisions based on the training
data. These systems include, but are not limited, expert systems,
fuzzy logic, non-linear regression analysis, multivariate analysis,
decision tree classifiers, Bayesian belief networks and, as
exemplified herein, neural networks.
[0066] As used herein, an adaptive machine learning process refers
to any system whereby data are used to generate a predictive
solution. Such processes include those effected by expert systems,
neural networks, and fuzzy logic.
[0067] As used herein, an expert system is a computer-based problem
solving and decision-support system based on knowledge of its task
and logical rules or procedures for using the knowledge. The
knowledge and the logic are entered into the computer from the
experience of human specialists in the area of expertise.
[0068] As used herein, a neural network, or neural net, is a
parallel computational model comprised of densely interconnected
adaptive processing elements. In the neural network, the processing
elements are configured into an input layer, an output layer and at
least one hidden layer. Suitable neural networks are known to those
of skill in this art (see, e.g., U.S. Pat. Nos. 5,251,626;
5,473,537; and 5,331,550, Baxt (1991) "Use of an Artificial Neural
Network for the Diagnosis of Myocardial Infarction," Annals of
Internal Medicine 115:843; Baxt (1992) "Improving the Accuracy of
an Artificial Neural Network Using Multiple Differently Trained
Networks," Neural Computation 4:772; Baxt (1992) "Analysis of the
clinical variables that drive decision in an artificial neural
network trained to identify the presence of myocardial infarction,"
Annals of Emergency Medicine 21:1439; and Baxt (1994) "Complexity,
chaos and human physiology: the justification for non-linear neural
computational analysis," Cancer Letters 77:85).
[0069] As used herein, a processing element, which also may be
known as a perceptron or an artificial neuron, is a computational
unit which maps input data from a plurality of inputs into a single
binary output in accordance with a transfer function. Each
processing element has an input weight corresponding to each input
which is multiplied with the signal received at that input to
produce a weighted input value. The processing element sums the
weighted inputs values of each of the inputs to generate a weighted
sum which is then compared to the threshold defined by the transfer
function.
[0070] As used herein, a transfer function, also known as a
threshold function or an activation function, is a mathematical
function which creates a curve defining two distinct categories.
Transfer functions may be linear, but, as used in neural networks,
are more typically non-linear, including quadratic, polynomial, or
sigmoid functions.
[0071] As used herein, an image is a multi-dimensional array of
data points, where each data point is represented by a number, or a
set of numbers, and where there is a relationship between adjacent
points in each of the dimensions. The index values in each
dimension typically represent a linear relationship, like position
or time, but are not limited to these types of relationships. A
single digitized scan line from a TV frame would be considered a
two dimensional image. In the case of the preferred embodiment, an
image refers to a one-dimensional set of pixels, which encode the
intensity of the color on the test strip.
[0072] As used herein, classifying an image refers to associating
an object or state with the image. Images of fruit might be
classified as to the type of fruit shown in the image. In the case
of the preferred embodiment, classifying the test strip image
refers to associating the positive or negative state with the
image.
[0073] As used herein, reconstructing an image refers to producing
an image from a mathematical function. When an image is represented
by a mathematical function, there may be errors in the
representation due to any number of factors.
[0074] As used herein, backpropagation, also known as backprop, is
a training method for neural networks for correcting errors between
the target output and the actual output. The error signal is fed
back through the processing layer of the neural network, causing
changes in the weights of the processing elements to bring the
actual output closer to the target output.
[0075] As used herein, Quickprop is a backpropogation method that
was proposed, developed and reported by Fahlman ("Fast Learning
Variations on Back-Propagation: An Empirical Study," Proceedings on
the 1988 Connectionist Models Summer School, Pittsburgh, 1988, D.
Touretzky, et al., eds., pp. 38-51, Morgan Kaufmann, San Mateo,
Calif.; and, with Lebriere, "The Cascade-Correlation Learning
Architecture," Advances in Neural Information Processing Systems 2,
(Denver, 1989), D. Touretzky, ed., pp. 524-32. Morgan Kaufmann, San
Mateo, Calif.).
[0076] As used herein, diagnosis refers to a predictive process in
which the presence, absence, severity or course of treatment of a
disease, disorder or other medical condition is assessed. For
purposes herein, diagnosis will also include predictive processes
for determining the outcome resulting from a treatment.
[0077] As used herein, risk refers to a predictive process in which
the probability of a particular outcome is assessed.
[0078] As used herein, a patient or subject includes any mammals
for whom diagnosis is contemplated. Humans are the preferred
subjects.
[0079] As used herein, biochemical test data refers to data from
any analytical methods, which include, but are not limited to:
immunoassays, bioassays, including nucleic acid and protein based
assays, chromatography, data from monitors, and imagers;
measurements and also includes data related to vital signs and body
function, such as pulse rate, temperature, blood pressure, data
generated by, for example, EKG, ECG and EEG, biorhythm monitors and
other such information. The analysis can assess for example,
chemical analytes, serum markers, antibodies, protein, nucleic
acids and other such material obtained from the patient through a
sample. Immunoassays are exemplified herein, but such
exemplification is not intended to limit the intended scope of the
disclosure, which is applicable to any test strip and test data
read by an instrument, particularly a reflectance reader.
[0080] As used herein, patient historical data refers to data
obtained from a patient, such as by questionnaire format, but
typically does not include biochemical test data as used herein,
except to the extent such data is historical, a desired solution is
one that generates a number or result whereby a diagnosis of a
disorder can be generated.
[0081] As used herein, a run is defined as a group of tests that
include a at least one of a positive reference, positive control,
negative control and any number of clinical samples within a 24 hr.
period.
[0082] As used herein, symbology refers to a code, such as a bar
code, that is engraved or imprinted on the test device. The
symbology is any code known or designed by the user. The symbols
are associated with information stored in a remote computer or
memory or other such device or means. For example, each test device
can be uniquely identified with an encoded symbology. It is
contemplated herein that identifying and other information can be
encoded in the bar code, which can be read by the reader when the
test strip is read. Alternatively, the bar code or other symbology
may be read by any of reading device known to those of skill in the
art.
[0083] As used herein, a bar code is a symbology, typically a field
of alternating dark bars and reflective spaces of varying widths,
that is affixed onto or associated with an item and provides
identifying information about the item. Bar codes can placed on a
reflective background, and the contrast between the dark bars and
reflective spaces, or the reflectivity ratio, allows an optical
sensor in a reader to discern the transitions between the bars and
spaces in the symbol. Bar codes are electro-optically scanned,
typically using a laser or LED, and generate a signal that is
transmitted to an associated computer whose memory has digitally
stored therein identifying information associated with the item.
The item is thereby automatically identified by its bar code and
can be tracked, or additional information can be added to the
stored information associated with the encoded item.
[0084] Several bar code formats are available and are used for
different purposes. A number of different bar code symbologies
exist, these symbologies include UPC/EAN codes, Code 39, Code 128,
Codeabar, Interleaved 2 of 5 and many others; two-dimensional
codes, such as PDF 417, Code 49, Code 16K; matrix codes (Data Code,
Code 1, Vericod); graphic codes; and any others known to those of
skill in the art. Preferred herein are one-dimensional codes, such
as the well known Code 39 and Code 128, although two-dimensional
codes (see, e.g., U.S. Pat. Nos. 5,243,655 and 5,304,786, also are
suitable for use herein.
[0085] The 39 bar code was developed in 1974 to provide a fully
alphanumeric bar code for data entry systems. This bar code is
especially effective in applications that use alphanumeric data for
item identification. The structure of 39 permits it to be printed
by a wide variety of techniques, including offset, letterpress,
fully-formed impact printers, dot matrix printers, and on-impact
printing devices.
[0086] Current application areas include inventory control,
manufacturing work-in-process, tracking, wholesale distribution,
hospitals, government agencies and retail point of sale. Code 39 is
the most widely used alphanumeric bar code. It has been accepted as
a standard code by many companies and industries. Specification
ANSI Draft MH10.X-1981, entitled, "Specifications for Bar Code
Symbols on Transport Packages & Unit Loads," describes three
different bar code symbologies. Code 39 is called 3-of-9 code in
the ANSI specification. Moreover, the Depae MIL-STD-1189, dated
Jan. 4, 1982, defines 39 (called 3 of 9 code) as the standard
symbology for marking unit packs, outer containers, and selected
documents.
[0087] Code 39 includes 9 bits, at least three of which are always
1. Code 39 can be used to encode a set of 43 characters, including
upper case alphabetic and numeric (0-9) characters, as well as
seven special characters (-, ., , *, $, /, + and %). The beginning
and end characters are always an asterisk (*). The code uses narrow
and wide bars along with narrow and wide spaces, and the encoding
for a single character is made up of a pattern of bars and spaces.
The code structure is three wide elements out of a total of nine
elements, where an element is the area occupied by a bar or space).
The nine elements include five bars and four spaces.
[0088] In Code 128, every character is constructed of eleven bars
and spaces, and all 128 ASCII characters, i.e., numeric characters,
upper and lower case characters, punctuation and control codes are
encoded. There are three different character sets to select from:
one set encodes all upper case characters and all ASCII control
characters; another encodes all upper and lower case characters;
and the third encodes all numeric characters. Through the use of
special characters, it is possible to switch between character sets
within a single code symbol. Code 128 uses four different bar and
space widths. Each data character encoded in a Code 128 symbol is
made up of 11 black or white modules. Three bars and three spaces
are formed out of the 11 modules. There are 106 different three
bar/three space combinations. Bars and spaces can vary between one
and four modules wide. The stop character is made up of 13 modules.
The symbol includes a quiet zone (10.times.-dimensions), a start
character, the encoded data, a check character, the stop character
and a trailing quiet zone (10.times.-dimensions) (see, e.g., U.S.
Pat. No. 5,262,625).
[0089] Systems for generating and reading bar codes are readily
available and are well known in the art.
Point of Care Diagnostic and Risk Assessment Systems
[0090] Provided herein are systems for use at the point of care for
diagnosing and assessing certain medical risks. The systems are
designed for use on site at the point of care, where patients are
examined and tested, and for operation remote from the site.
[0091] The systems are designed to accept input in the form of
patient data, including, but not limited to biochemical test data,
physical test data, historical data and other such data, and to
process and output information, preferably data relating to a
medical diagnosis or a disease risk indicator. The patient data may
be contained within the system, such as medical records or history,
or may be input as a signal or image from a medical test or
procedure, for example, immunoassay test data, blood pressure
reading, ultrasound, X-ray or MRI, or introduced in any other form.
Specific test data can be digitized, processed and input into the
medical diagnosis expert system, where it may be integrated with
other patient information. The output from the system is a disease
risk index or medical diagnosis.
[0092] In a preferred embodiment, the system includes a reader,
such as a reflectance or transmission reader, preferably a
reflectance reader, for reading patient data, a test device
designed to be read in the reader, and software for analysis of the
data. In an exemplified embodiment of the system, the reader is the
reflectance reader provided herein. A test strip device in a
plastic housing designed for use with the reader, optionally
including a symbology, such as an alphanumeric character bar code
or other machine-readable code, and software designed for analysis
of the data generated from the test strip also are provided.
Assays
[0093] Any assay is intended for use in the systems and methods
herein. Such assays include, but are not limited to: nucleic acid
detection, including using amplification and non-amplification
protocols, any assay that relies on colorimetric or spectrometric
detection, including fluorometric, luminescent detection, such as
creatine, hemoglobin, lipids, ionic assays, blood chemistry. Any
test that produces a signal, or from which a signal can be
generated, that can be detected by a detector, such as a
photodetector or a gamma counter, is intended for use as part of
the systems provided herein. Any wavelength is intended to be
included.
[0094] Immunoassays, including competitive and non-competitive
immunoassays, are among those preferred for determination of the
presence or amount of analyte in a patient sample, and are
exemplified herein. It is understood that immunoassays are provided
for exemplification, and that the methods and systems provided
herein have broad applicability to patient test data and other test
data.
[0095] A number of different types of immunoassays are well known
using a variety of protocols and labels. Immunoassays may be
homogeneous, i.e. performed in a single phase, or heterogeneous,
where antigen or antibody is linked to an insoluble solid support
upon which the assay is performed. Sandwich or competitive assays
may be performed. The reaction steps may be performed
simultaneously or sequentially. Threshold assays may be performed,
where a predetermined amount of analyte is removed from the sample
using a capture reagent before the assay is performed, and only
analyte levels of above the specified concentration are detected.
Assay formats include, but are not limited to, for example, assays
performed in test tubes, wells or on immunochromatographic test
strips, as well as dipstick, lateral flow or migratory format
immunoassays.
[0096] Any known immunoassay procedure, particularly those that can
be adapted for use in combination with lateral flow devices as
described herein, can be used in the systems and methods provided
herein.
Test Device
[0097] Any device which is compatible for use with a reader,
preferably a reflectance reader, for determining the assay result
is contemplated for use herein. Any such test strips that can be
adapted for use in combination with a reader are contemplated for
use in the systems provided herein. Such test strip devices as are
known to those of skill in the art (see, e.g., U.S. Pat. Nos.
5,658,801, 5,656,502, 5,591,645, 5,500,375, 5,252,459, 5,132,097
and many other examples) may be used in systems as described
herein, particularly in combination with the reader provided
herein.
[0098] Typically these test devices are intended for use with
biological samples, such as saliva, blood, serum, cerebral spinal
fluid, cervico-vaginal samples, for example. Other biological
samples, such as food samples, which are tested for contamination,
such as by bacteria or insects, also are contemplated. Target
analytes include, but are not limited to: nucleic acids, proteins,
peptides, such as human immunodeficiency virus (HIV) antigens,
antigens indicative of bacterial, such as Salmonella and E. coli,
yeast or parasitic infections, apolipoprotein(a) and
lipoprotein(a), environmental antigens, human chorionic
gonadotropin (hCG), E-3-G, interleukins and other cytokines and
immunomodulatory proteins, such as IL-6 and interferon, small
nuclear ribonuclear particles (snRNP) antigens, fFN and other
indicators, such as IGF binding protein-1, of pregnancy related
disorders.
[0099] Immunoassay Test Strip
[0100] A preferred embodiment is an immunoassay test strip that
includes a membrane system that defines a liquid flow pathway. An
exemplary immunoassay test strip provided herein is shown in FIGS.
1A and 1B. The test strip is described in detail in EXAMPLE 1. This
test strip is provided for purposes of exemplification of the
methods and systems provided herein and is not intended to limit
the application to immunoassay test strip devices.
[0101] For performing immunoassays, lateral flow test immunoassay
devices are among those preferred herein. In such devices, a
membrane system forms a single fluid flow pathway along the test
strip. The membrane system includes components that act as a solid
support for immunoreactions. For example, porous or bibulous or
absorbent materials may be placed on a strip such that they
partially overlap, or a single material can be used, in order to
conduct liquid along the strip. The membrane materials may be
supported on a backing, such as a plastic backing. In a preferred
embodiment, the test strip includes a glass fiber pad, a
nitrocellulose strip and an absorbent cellulose paper strip
supported on a plastic backing.
[0102] Antibodies that react with the target analyte and/or a
detectable label system are immobilized on the solid support. The
antibodies may be bound to the test strip by adsorption, ionic
binding, van der Waals adsorption, electrostatic binding, or by
covalent binding, by using a coupling agent, such as
glutaraldehyde. For example, the antibodies may be applied to the
conjugate pad and nitrocellulose strip using standard dispensing
methods, such as a syringe pump, air brush, ceramic piston pump or
drop-on-demand dispenser. In a preferred embodiment, a volumetric
ceramic piston pump dispenser is used to stripe antibodies that
bind the analyte of interest, including a labeled antibody
conjugate, onto a glass fiber conjugate pad and a nitrocellulose
strip.
[0103] The test strip may or may not be otherwise treated, for
example, with sugar to facilitate mobility along the test strip or
with water-soluble non-immune animal proteins, such as albumins,
including bovine (BSA), other animal proteins, water-soluble
polyamino acids, or casein to block non-specific binding sites.
[0104] Test Strip Housing
[0105] The test strip optionally may be contained within a housing
for insertion into the reflectance reader. The housing may be made
of plastic or other inert material that does not interfere with the
assay procedure. An exemplary assay device, including a test strip
and housing assembly is shown in FIGS. 2A-5.
[0106] In a preferred embodiment, the test strip housing includes a
symbology, such as a bar code that can be associated with data
related to the assay device, patient data and/or test run. For
example, information associated with the device, such as lot
number, expiration date, analyte and intensity value, or
information related to the test run, such as date, reflectance
value or other such information, can be encoded and associated,
such as in a database with a bar code imprinted on the device. Any
bar code system that provides the appropriate line thickness and
spacing can be used. Code 39 and Code 128 are among the preferred
bar code systems.
[0107] In a particular embodiment, Code 39 is used. An example bar
code is shown in FIG. 25. The bar code is made up of 11
alphanumerics, including 2 alphabetic and 9 numeric characters. The
first and last characters are asterisks (*), as is standard in the
Code 39 system. The lot number is stored as 1 alpha and 4 numeric
codes so that product complaints or questions can be traced to a
particular lot number. In the exemplified embodiment, the first
character represents the month of production, the second is a digit
representing the year of production and the last three are an index
value indicating the lot number. Thus, the lot number "A8001"
represents the first device in a lot produced in January, 1998. The
next two characters ("01") represent the identity of the analyte as
2 numerics (00-99). This permits the use of up to 100 different
analytes with the system. The reflectance intensity value (00-99)
is stored as the next two numeric characters ("01"). The intensity
value sets the reference threshold for which controls and patient
samples can be compared. This eliminates the need to run liquid
reference samples on a daily basis. FIGS. 2A, 2B and 3 depict assay
devices that optionally include bar codes, 216 and 316,
respectively. Finally, the cassette expiration date is stored as 1
alpha and 1 numeric code to prevent the use of expired devices. In
the example given, an expiration code of "A9" represents an
expiration date of January, 1999.
[0108] Antibodies
[0109] Any antibody, including polyclonal or monoclonal antibodies,
or any fragment thereof, such as the Fab fragment, that binds the
analyte of interest, is contemplated for use herein. Monoclonal
and/or polyclonal antibodies may be used. For example, a mouse
monoclonal anti-fetal fibronectin antibody may be used in a labeled
antibody-conjugate for detecting fetal fibronectin, and a
polyclonal goat anti-mouse antibody also may be used to bind fetal
fibronectin to form a sandwich complex. An antibody that binds to
the labeled antibody conjugate that is not complexed with fetal
fibronectin may be immobilized on the test strip and used as a
control antibody. For example, when fetal fibronectin is the
analyte, a polyclonal goat anti-mouse IgG antibody may be used.
[0110] Conjugation of the Antibody to a Label
[0111] An antibody conjugate containing a detectable label may be
used to bind the analyte of interest. The detectable label used in
the antibody conjugate may be any physical or chemical label
capable of being detected on a solid support using a reader,
preferably a reflectance reader, and capable of being used to
distinguish the reagents to be detected from other compounds and
materials in the assay.
[0112] Suitable antibody labels are well known to those of skill in
the art. The labels include, but are not limited to
enzyme-substrate combinations that produce color upon reaction,
colored particles, such as latex particles, colloidal metal or
metal or carbon sol labels, fluorescent labels, and liposome or
polymer sacs, which are detected due to aggregation of the label. A
preferred label is a colored latex particle. In an alternative
embodiment, colloidal gold is used in the labeled antibody
conjugate.
[0113] The label may be derivatized for linking antibodies, such as
by attaching functional groups, such as carboxyl groups to the
surface of a particle to permit covalent attachment of antibodies.
Antibodies may be conjugated to the label using well known coupling
methods. Coupling agents such as glutaraldehyde or carbodiimide may
be used. The labels may be bonded or coupled to the antibodies by
chemical or physical bonding. In a preferred embodiment, a
carbodiimide coupling reagent,
1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDAC), is used to
link antibodies to latex particles.
[0114] Measurement of Analytes
[0115] Any analyte that can be detected in any assay, particularly
calorimetric assays, including immunoassays, and that can be
associated with a disorder is contemplated as a target herein.
Suitable analytes are any which can be used, along with a specific
binding partner, such as an antibody, or a competitor, such as an
analog, in an assay. Analytes may include, but are not limited to
proteins, haptens, immunoglobulins, enzymes, hormones (e.g., hCG,
LH, E-3-G estrone-3-glucuronide and P-3-G
(progestrone-3-glucuronide)), polynucleotides, steroids,
lipoproteins, drugs, bacterial or viral antigens, such as
Streptococcus, Neisseria and Chlamydia, lymphokines, cytokines, and
the like. A number of suitable analytes are described in U.S. Pat.
No. 5,686,315, which is incorporated herein by reference. Although
examples are provided for the determination of fetal fibronectin in
cervicovaginal samples, the systems and methods provided herein are
not limited to the detection and measurement of fetal fibronectin,
but apply to any biochemical test, particularly those for which
test strips can be developed or for which test strips are
known.
[0116] Measurement of Fetal Fibronectin
[0117] In an exemplary embodiment, the system is used for
diagnosing or predicting conditions such as pregnancy, including
ectopic pregnancy, pre-eclampsia, preterm labor or imminent
delivery and fetal membrane rupture. Fetal fibronectin is a fetal
restricted antigen found in placenta, amniotic fluid and fetal
connective tissue. Since fetal fibronectin is strictly associated
with pregnancy, determination of the presence of fetal fibronectin
in a cervicovaginal sample is a highly reliable early indication of
pregnancy. Also, the absence of a fetal restricted antigen in a
cervicovaginal sample during the first 20 weeks of pregnancy is an
indicator of ectopic pregnancy. Ectopic pregnancies, which are a
major cause of mortality for women, are not readily distinguished
from normal pregnancies using standard pregnancy determination
methods and tests. Determination of impending preterm births is
critical for increasing neonatal survival of preterm infants. The
presence of fetal fibronectin (fFN) in cervicovaginal secretion
samples in patients after week 12 of pregnancy is associated with a
risk of impending delivery, including spontaneous abortions (12-20
weeks), preterm delivery (20-37 weeks), term (37-40 weeks) and
post-date delivery (after 40 weeks), in pregnant women. In
addition, the presence of fetal fibronectin in a cervicovaginal
sample provides a method for determining increased risk of labor
and fetal membrane rupture after week 20 of pregnancy. Detection of
rupture of the amniotic membrane is important in distinguishing
true and false labor, and when the rupture is small and the volume
of amniotic liquid escaping is small, the rupture is often
undetected. The methods and systems herein provide a means to
reliably assess the risk for any of these conditions. An
immunoassay procedure for detecting fetal fibronectin is described
in EXAMPLE 2.
[0118] Test Strip for Measuring fFN and Cellular Fibronectin
[0119] Methods for measuring fetal fibronectin and cellular
fibronectin levels in cervicovaginal samples are known (see, U.S.
Pat. Nos. 5,096,830, 5,185,270, 5,223,440, 5,236,846, 5,281,522,
5,468,619 and 5,516,702, each of which is incorporated herein by
reference in its entirety), and diagnostic tests for various
pregnancy-related disorders are available (see, e.g., U.S. Pat.
Nos. 5,096,830, 5,079,171). These methods can be adapted for use
with the immunoassay test strips and devices described herein. In
particular, an immunoassay test strip for measuring fFN in
cervicovaginal samples is provided.
Antibodies for Fetal Fibronectin
[0120] An antibody that will bind the analyte of interest is
conjugated to a detectable label. In a particular embodiment, where
fetal fibronectin is to be detected, a mouse monoclonal anti-fFN
antibody (see, U.S. Pat. No. 5,281,522), conjugated to latex
particles containing a blue dye may be used. In an alternative
embodiment, a goat polyclonal antibody to human fibronectin is
conjugated to a colloidal gold label.
[0121] In a preferred embodiment, an antibody that binds the
labeled antibody conjugate that is not complexed with fetal
fibronectin is used as a control antibody. For example, where the
labeled conjugate includes a monoclonal anti-fetal fibronectin
antibody, a polyclonal goat anti-mouse IgG antibody is used.
[0122] The antibodies may be raised and purified using methods
known to those of skill in the art or obtained from publicly
available sources. For example, monoclonal antibody FDC-6
(deposited at the American Type Culture Collection as accession
number ATCC HB 9018; see U.S. Pat. No. 4,894,326; see, also,
Matsuura et al. (1985) Proc. Natl. Acad. Sci. U.S.A. 82:6517-6521;
see, also, U.S. Pat. Nos. 4,919,889, 5,096,830, 5,185,270,
5,223,440, 5,236,846, 5,281,522, 5,468,619 and 5,516,702), which is
raised against whole molecule onco-fetal fibronectin from a tumor
cell line, may be used.
Fetal Fibronectin Assay Procedure
[0123] In conducting the assay, a patient sample is obtained. The
sample may include fluid and particulate solids, and, thus, can be
filtered prior to application to the assay test strip. The sample
may be removed from the patient using a swab having a fibrous tip,
an aspirator, suction or lavage device, syringe, or any other known
method of removing a bodily sample, including passive methods for
collecting urine or saliva. In particular, the sample may be
extracted into a buffer solution, and optionally heated, for
example, at 37.degree. C. and filtered. In a preferred embodiment,
where fetal fibronectin is to be detected in a sample, the sample
is obtained from in the vicinity of the posterior formix, the
ectocervix or external cervical os using a swab having a dacron or
other fibrous tip.
[0124] A volume of the test sample is then delivered to the test
strip (FIGS. 1A and 1B) using any known means for transporting a
biological sample, for example, a standard plastic pipet. Any
analyte in the sample binds to the labeled antibody and the
resulting complex migrates along the test strip. Alternatively, the
sample may be pre-mixed with the labeled conjugate prior to
applying the mixture to the test strip. When the labeled
antibody-analyte complex encounters a detection zone of the test
strip, the immobilized antibody therein binds the complex to form a
sandwich complex, thereby forming a colored stripe.
[0125] Any unbound latex-conjugated antibody continues to migrate
into a control zone where it is captured by a second immobilized
antibody or other agent capable of binding the conjugate, and
thereby forms a second colored stripe due to the aggregation of the
dye-containing latex beads. This indicates that the assay run has
completed.
[0126] The results of the assay are assessed using the reader and
software provided herein. The rapid test herein provides, at the
very least, the same clinically relevant information as a fFN ELISA
(an enzyme linked immunosorbent sandwich assay (ELISA) see, e.g.,
U.S. Pat. No. 5,281,522) test heretofore available, but in
significantly less time and at the point of care. This rapid fFN
immunoassay allows the user to test a cervicovaginal swab sample in
about 20 minutes. When comparing the 20 minute rapid fFN test to
the data from the fFN ELISA, a Kappa coefficient of 0.68 was found
with a 95% confidence interval [0.62, 0.76] and an overall
concordance of at least about 91.6%. These data were obtained using
a system including an immunoassay test strip in combination with a
reflectance reader and data processing software employing data
reduction and curve fitting algorithms or neural networks, as
described herein. Thus, the systems herein provide results that are
at the very least comparable to the ELISA, but generally are
superior and more informative.
Reader
[0127] Reflectance and other readers, including densitometers and
transmittance readers, are known to those of skill in the art (see,
e.g., U.S. Pat. Nos. 5,598,007, 5,132,097, 5,094,955, 4,267,261,
5,118,183, 5,661,563, 4,647,544, 4,197,088, 4,666,309, 5,457,313,
3,905,767, 5,198,369, 4,400,353). Any reader that upon combination
with appropriate software, as described herein, can be used to
detect images and digitize images, such as symbologies,
particularly bar codes or the lines and stripes produced on
chromatographic immunoassay devices or on gels or photographic
images thereof, such as the lines on DNA and RNA sequencing gels,
X-rays, electrocardiograms, and other such data, is intended for
use herein.
[0128] The reader provided herein, particularly in combination with
the software provided herein, is preferred for use in the point of
care diagnostic systems.
[0129] In an exemplified embodiment, a sample is applied to a
diagnostic immunoassay test strip, and colored or dark bands are
produced. The intensity of the color reflected by the colored label
in the test region (or detection zone) of the test strip is, for
concentration ranges of interest, directly proportional or
otherwise correlated with an amount of analyte present in the
sample being tested.
[0130] The color intensity produced is read, in accordance with the
present embodiment, using a reader device, for example, a
reflectance reader, adapted to read the test strip. The intensity
of the color reflected by the colored label in the test region (or
detection zone) of the test strip is directly proportional to the
amount of analyte present in the sample being tested. In other
words, a darker colored line in the test region indicates a greater
amount of analyte, whereas a lighter colored line in the test
region indicates a smaller amount of analyte. In accordance with
the present embodiment, the color intensity produced, i.e., the
darkness or lightness of the colored line, is read using a reader
device, for example, a reflectance reader, adapted to read the test
strip. A reflectance measurement obtained by the reader device is,
in accordance with the present embodiment, correlated to the
presence and/or quantity of analyte present in the sample as
described hereinbelow. The reader takes a plurality of readings
along the strip, and obtains data that are used to generate results
that are an indication of the presence and/or quantity of analyte
present in the sample as described hereinbelow. The system also
correlates such data with the presence of a disorder, condition or
risk thereof.
[0131] Optionally, in addition to reading the test strip, the
reader may be adapted to read a symbology, such as a bar code,
which is present on the test strip or housing and encodes
information relating to the test strip device and/or test result
and/or patient, and/or reagent or other desired information.
Typically the associated information is stored in a remote computer
database, but can be manually stored. In other embodiments, the
symbology can be imprinted when the device is used and the
information encoded therein.
[0132] Referring to FIG. 6, an exemplary embodiment of the reader
device 600 is shown with an immunoassay device 200, as shown in
FIG. 2A, inserted into a cassette slot 602 therein. The cassette
slot 602 is adapted to receive the immunoassay device 200, and a
reader head assembly (not shown) supported within the reader device
600 is adapted to read the immunoassay test strip, and optionally a
symbology, exemplified as a bar code, with the immunoassay device.
Such reading is performed by scanning a reader head (not shown)
across the device, including a test window 214 in the immunoassay
device 200 and a symbology, such as the exemplified bar code 216,
if present, and in the process directing light onto the bar code
and/or a test portion and a control portion of the immunoassay test
strip. An amount of such light reflected back from the bar code
and/or the test portion and control portion of the immunoassay test
strip is measured as the reader head scans across the device.
[0133] Also shown are a data entry keypad 604, including ten digit
keys (also labeled with letters of the alphabet, such as is
commonly the case on telephone keypads), a delete key, a space key,
an escape key, a print key, enter key, and up, down, left and right
arrow keys, additional characters such as , or . or /, and any
others desired by the user. The data entry keypad 604 can be used
by an operator of the reader device 600 to input identification
information, to enter control test parameters, to initiate and
terminate testing, and the like. A processing unit (not shown)
housed within the reader device 600 is responsive to the keypad and
performs data analysis functions, as described hereinbelow, in
accordance with modifications made to a processor in the processing
unit by an appropriate software subsystem.
[0134] Also shown in FIG. 6 is a liquid crystal display screen 606.
The liquid crystal display screen 606 receives output data from the
processing unit and displays it to an operator of the reader device
600, including displaying results of tests, error messages,
instructions, troubleshooting information, and the like.
[0135] Referring next to FIG. 7, a perspective view of a lower
housing 702 of one embodiment of an immunoassay reader device 600
of FIG. 6 is shown with a reader head assembly 704 located therein
and the immunoassay device 200 inserted into the cassette slot 602
at a front edge of the lower housing 702. The cassette slot 602
located at the front edge of the lower housing 702 provides an
aperture through which the immunoassay device 200 is inserted into
and guided into the reader device 600 in order measure light
reflected from an immunoassay test strip. In some embodiments of
the reader, the reader is adapted to additionally read a symbology,
such as a bar code, imprinted, engraved on or otherwise affixed to
the test strip or device.
[0136] When the immunoassay device 200 is inserted into the
cassette slot 602 of the lower housing, a reader head 706 on the
reader head assembly 704 is positioned directly above the device
200, such that the longitudinal (or major) axes of optical fibers
within the reader head 706 are normal to a surface of the device,
including the test strip and optionally a symbology that is
imprinted, engraved or other wise affixed on the device.
[0137] Alternatively, the reader head 706 may be fixed, at least
rotationally, and the immunoassay device 200 may be moved into
position after insertion into the cassette slot 602, such that the
longitudinal (or major) axes of optical fibers within the reader
head 706 are normal to a surface of the device to be read by the
reader.
[0138] Referring next to FIG. 8, a top view is shown of the lower
housing 702, the immunoassay device 200, the cassette slot 602, and
a stepper motor 802. As can be seen, after insertion into the lower
housing 702, the immunoassay device 200 is positioned in alignment
with the stepper motor 802, which is part of the reader head
assembly. The stepper motor is used to scan the reader head 706
across the symbology, such as the exemplified bar code 216 and/or
test window 214 of the immunoassay device 200.
[0139] One embodiment of the reader device is shown in FIG. 9.
Shown are the lower housing 702, the immunoassay device 200, the
stepper motor 802, an actuator wheel 902, the reader head 706, and
linkages for moving the reader head 706 parallel to a major axis of
the immunoassay device 200 in order to scan the reader head 706
across the symbology (bar code) 216 and/or test window 214 of the
immunoassay device 200.
[0140] To read the immunoassay test strip, the reader head is
brought within a uniform distance of about 0.010 inches from the
test strip. When the immunoassay device 200 is slid into the
cassette slot 602, the actuator wheel 902 and an actuator spring
(not shown) work together to bring the reader head 706 down to
within about 0.010 inches of the immunoassay test strip within the
housing 202 of the immunoassay device 200. In order to move the
reader head 706 into position within 0.010 inches of the
immunoassay test strip, the reader head 706 is pivoted along with a
portion of the reader head assembly. Prior to being brought into
position within 0.010 inches of the immunoassay test strip, while
the immunoassay device 200 is being inserted into or removed from
the immunoassay reader device 600, the reader head 706 assumes a
retracted position, i.e., raised position, so that the immunoassay
device 200 can be inserted into or removed from the immunoassay
reader device 600 without crashing the reader head 706 into the
immunoassay device 200.
[0141] When the immunoassay device 200 is inserted into the
cassette slot 602, it contacts the actuator wheel 902 and causes a
carriage assembly of the reader head assembly to be brought down
from the retracted position so that the reader head 706 is within
0.010 inches of the immunoassay test strip.
[0142] Insertion of the immunoassay device 200 causes the actuator
wheel to pop-up by applying pressure to the actuator spring,
bringing the carriage assembly down from the retracted
position.
[0143] The immunoassay device 200 is pushed into the cassette slot
602 until it meets a stop. Once inserted, the immunoassay device
200, the actuator wheel 902, and the actuator spring remain fixed
in position, while the reader head 706 is stepped across the test
window 214 of the immunoassay device 200 by the stepper motor 802.
In other words, only the reader head 706 moves during the scanning
of the immunoassay test strip.
[0144] Alternatively, the immunoassay device 200 is pushed into the
cassette slot 602 until it meets the stop. Once inserted the
immunoassay device 200 may be rotated up to within 0.010 inches of
the reader head 706 by gently lifting the immunoassay device 200.
By gently lifting the immunoassay device 200, a base of the reader
head assembly is pivoted up toward the carriage assembly and the
reader head 706, positioning the immunoassay test strip within
0.010 inches of the reader head 706. Then the reader head 706 is
then stepped across the test window 214 of the immunoassay test
strip by the stepper motor 802. In other words, in accordance with
this alternative, only the reader head 706 moves during the
scanning of the immunoassay test strip and, the reader head 706
moves only during the scanning of the immunoassay test strip.
[0145] Prior to insertion of the immunoassay device 200 into the
cassette slot 602, and prior to scanning, the reader head 706 is
positioned at a point that would place it approximately half way
across (in the middle of) the test window 214 of the immunoassay
device 200. After insertion of the device 200 into the reader 600,
when an operator depresses a scan key on the key pad (see FIG. 6),
the reader head 706 is moved from this position toward the stepper
motor 802 until a microswitch is activated. Once the microswitch is
activated, the reader head 706 is said to be in a "home" position
from which scanning of the test strip commences. Once scanning
commences, the reader head 706 advances from the home position
across the test window 214. Thus, the reader head 706 scans in a
direction moving away from the stepper motor toward the cassette
slot 602 or to the left as depicted in FIG. 9. Total travel of the
reader head 706 during scanning of the immunoassay test strip is
0.452 inches, which is achieved in 0.002 inch steps, which are 226
in number. One set of readings is taken per step, with each set of
readings including a dark reading, a first light reading and a
second light reading.
[0146] Referring next to FIG. 10, the reader head assembly 1000 is
shown. Shown are the actuator spring 1002, the actuator 1004, the
base 1006, the stepper motor 802, the actuator wheel 902, a rotor
arm 1008, and the reader head 706. Also shown is a pivot point 1010
on which the carriage assembly 1012, including the reader head 706,
stepper motor 802, actuator wheel 902, actuator spring, 1002, and
rotor arm 1008 pivot to assume a raised position for insertion and
removal of the immunoassay device 200 from the reader device 600
and to assume a lowered position for scanning the reader head 706
across the test window 214 of the immunoassay device 200.
[0147] Referring next to FIG. 11, shown is a side view of the
reader head 706 of the reader head assembly of FIG. 10. Shown is a
first light emitting diode (LED) 1102, a second light emitting
diode (LED) 1104, a photodetector 1106, a reader head aperture
1108, and mounting holes 1110.
[0148] Referring next to FIG. 12 a reverse angle side view is shown
of the reader head assembly 1000 of FIG. 10. Shown are the stepper
motor 802, the base 1006, mounting holes 1202, and a mounting
bracket 1204 on which the reader head 706 is mounted.
[0149] Referring next to FIG. 13 a reverse angle side view of the
reader head 706 of FIG. 11 is shown. Seen are the mounting holes
1110, and the reader head aperture 1108.
[0150] Referring next to FIG. 14, shown is a side view of the
reader head assembly 1000 of FIG. 10 having assumed a retracted
position. Shown are the actuator spring 1002, the actuator arm
1004, the stepper motor 802, the reader head 706, the reader head
supporting bracket 1204, the pivot 1010 on which such elements
rotate, and a base 1006 relative to which such elements rotate.
[0151] As can be seen, the actuator arm 1004, the actuator spring
1002, the stepper motor 802, the reader head 706, the reader head
mounting bracket 1204, and mechanisms used for supporting and
scanning the reader head 706 are designed so that the test strip
100 in the device 200 is positioned within 0.010 inches of the
aperture 1108 of the reader head. Any design suitable to effect
such can be employed with the present embodiment.
[0152] In the example illustrated, the actuator arm 1004, the
actuator spring 1002, the stepper motor 802, the reader head 706,
the reader head mounting bracket 1204, and the mechanisms used for
supporting and scanning the reader head 706 are shown rotated on
the pivot 1010 such as would be the case, in accordance with the
variation shown, when the immunoassay device 200 has been removed
from the reader device 600 and/or as the immunoassay device 200 is
being inserted into or removed from the reader device 600.
[0153] Referring next to FIG. 15, a side view is shown of the
reader head 706 of FIG. 11. Shown are the aperture 1108 and the
first light emitting diode 1102.
[0154] Referring next to FIG. 16, an end view is shown of the
reader head assembly 1000 of FIG. 10. Shown is the stepper motor
802, the base 1006, and the actuator arm 1004.
[0155] In alternative embodiments, the reader is adapted to read a
symbology, such as a bar code. An exemplary embodiment of a reader
so-adapted is shown in FIG. 24. In this embodiment, when the device
cassette 2402 is inserted into the reader, it sits on a spring
stage 2404. Prior to insertion of the device 300 (as shown in FIG.
2B) into the cassette slot 602, and prior to scanning, the reader
head 2406 is positioned at a point that would place it
approximately 0.125 inches from the forward edge of the device as
it is inserted into the reader.
[0156] As shown in FIG. 2B, the device includes guide ridges 318 on
either side of the bar code along the outer edges of the upper
surface of the device. The reader head 2406 is moved by the shaft
2408 of the stepper motor 2414 and scans in a direction moving away
from the stepper motor toward the cassette slot 2412. As the reader
head 2406 moves along the device above the bar code 2410, the guide
ridges 2412 contact the reader head assembly and act to compress
the spring stage 2404 by 3.degree. in order maintain the reader
head 2406 at a distance of 0.010 inches above the bar code 2410 as
the bar code 2410 is read. After the bar code 2410 is read, the
reader head assembly 2406 moves off the guide ridges 2412, the
spring stage 2404 returns to a level position (0.degree.), and the
reader head 2406 is repositioned at a distance of 0.010 inches in
order to read the test strip. When reading a symbology, such as a
bar code, the reader is moved in steps of approximately between
0.002-0.008 inches at a scan resolution of approximately 125-500
steps per inch, preferably about 250 steps per inch. One set of
readings is taken per step, with each set of readings including a
dark reading, a first light reading and a second light reading.
[0157] Regardless of whether one of these alternatives is used, or
whether any of numerous variations thereof or any of numerous other
possible embodiments well within the abilities of the skilled
artisan to easily produce is used in order to position the reader
head within a prescribed distance, e.g., 0.010 inches, of the test
strip symbology, such as a bar code, a suitable mechanism is
preferably employed to effect such positioning.
[0158] Referring next to FIG. 17, shown is a side view partially in
cross-section of an exemplary embodiment of the reader head. Shown
are a first light emitting diode 1102, a second light emitting
diode 1104 and a photodetector 1106. Also shown is an aperture 1108
and the mounting holes 1110. Shown coupled between each of the
LED's 1102, 1104 and the aperture 1108 are first and second
fiberoptic bundles 1702, 1704. Similarly, a third fiberoptic bundle
1706 is shown coupled between the aperture 1108 and the
photodetector 1106. The first and second fiberoptic bundles 1702,
1704 conduct light from the first and second LED's 1102, 1104,
respectively, to the aperture 1108. The third fiberoptic bundle
1706 conducts light from the aperture 1108 to the photodetector
1106. In response to such light, the photodetector generates a
reflection signal, e.g., a voltage indicative of an amount of
reflected light. The electrical signal can be then processed and
converted to a digital signal by using any method commonly known to
those of skill in the art.
[0159] Referring next to FIG. 18, shown is a closeup partial
cross-sectional view of the aperture 1108 of FIG. 17. Also shown
are individual fiberoptic fibers 1802, 1804, 1806 of the fiberoptic
bundles 1702, 1704, 1706 of FIG. 17, positioned within the aperture
1108 so as to transmit light 1808 from the aperture 1108 onto the
symbology (exemplified bar code) and/or test strip 100 and to
receive reflected light 1808 from the bar code and/or test strip
100 entering the aperture 1108. (The transmitted and reflected
light 1808 is represented with an arrow.) As can be seen, a gap
1810 between the aperture 1108 and the bar code and/or test strip
100 is present. The gap 1810 preferably has a width of
approximately 0.010 inches, which is maintained as the reader head
706 is scanned across the bar code and/or test window 214 of the
test strip 200.
[0160] Referring next to FIG. 19, a bottom view is shown of
individual fiberoptic fiber ends 1902, 1904, 1906 positioned in the
aperture 1108 of the reader head 706 of FIG. 10 so as to maximize
the distribution of light emitted from individual fiberoptic fibers
(fiberoptic conductors), and furthermore to maximize the uniformity
of light received into individual fiberoptic conductors. Indicated
using diagonal cross-hatching angled from lower left to upper right
are individual fiberoptic conductor ends 1902 of the first
fiberoptic bundle 1702. These individual fiberoptic conductor ends
1902 carry light emitted from the first light emitting diode from
the first fiberoptic bundle through the aperture 1108 of the reader
head 706. Similarly, indicated with cross-hatching from an upper
left to lower right are fiberoptic conductor ends 1904 of the
second fiberoptic bundle 1704. These individual fiberoptic
conductor ends carry light emitted from the second light emitting
diode to the aperture 1108 of the reader head 706. Without
cross-hatching are shown individual fiberoptic conductor ends 1906
of the third fiberoptic bundle 1706. The third fiberoptic bundle
1706 carries light entering the aperture 1108 to the
photodetector.
[0161] By employing the particularly advantageous arrangement of
the fiberoptic conductor ends 1902, 1904, 1906 at the aperture
1108, uniform distribution emissions and light reception is
achieved. Such arrangement is said to be a "sigmoidal" (S-like or
serpentine) arrangement or a "sigmoidal" distribution. It is an
important feature of the present embodiment that the fiberoptic
fibers in each of the three groups are arranged along with
fiberoptic fibers from the remaining groups in a sigmoidal-like (or
"S"-like) pattern with three columns of thirteen fiberoptic fibers
each. An arrangement that achieves this feature is intended
herein.
[0162] In order to achieve the sigmoidal arrangement of fiberoptic
conductor ends shown, 39 fiberoptic conductors are positioned
within the aperture 1108. Next, a clamp assembly made up of a
"U"-shaped channel, and an "I"-shaped clamp positioned at the open
side of the "U" is employed. The fiberoptic conductors, portions of
which protrude from the aperture 1108 are placed between the
"U"-shaped channel and the "I"-shaped clamp and a compressive force
is applied thereto by the "I"-shaped clamp, holding the protruding
portions of the fiberoptic conductors firmly in position. A resin
is then poured into the reader head 706 so as to become interposed
between and around the fiberoptic conductors at the aperture 1108.
Once the resin is set, the clamp assembly is removed, and the
protruding portions of the fiberoptic conductors are trimmed back
flush with the aperture 1108, so as to define a planar surface of
fiberoptic conductor ends 1902, 1904, 1906 at the aperture 1108.
This planar surface is held parallel to a plane at an upper surface
of the immunoassay test strip 100 during scanning of the
immunoassay test strip.
[0163] Advantageously, by creating this planar surface of
fiberoptic conductor ends 1902, 1904, 1906, the associated
fiberoptic conductors of which all of which have longitudinal axes
that are substantially parallel to one another and normal to the
plane defined by the fiberoptic conductor ends 1902, 1904, 1906. As
a result, very efficient transfer of light to and from the
fiberoptic conductor ends 1902, 1904, 1906 is achieved.
[0164] Once the fiberoptic conductor ends 1902, 1904, 1906 are set
in the resin, and trimmed, as described above, in individual
fiberoptic conductors are tested by projecting light individually
through the fiberoptic conductors toward the fiberoptic conductor
ends 1902, 1904, 1906, to locate the fiberoptic conductor end
associated with the particular fiberoptic conductor being tested.
This determination is made by observing which of the fiberoptic
conductor ends 1902, 1904, 1906 "lights up" when light is
transmitted down the particular fiberoptic conductor. As fiberoptic
conductors associated with the fiberoptic conductor ends 1902,
1904, 1906 are identified, the fiberoptic conductors are assigned
to one of the first, second, and third fiberoptic bundles, so as to
achieve, for example, the sigmoidal distribution of fiberoptic
conductor ends 1902, 1904, 1906 illustrated in FIG. 19.
[0165] Advantageously, by effecting the sigmoidal distribution of
fiberoptic conductor ends 1902, 1904, 1906 associated with
fiberoptic conductors of each of the first, second, and third
fiberoptic bundles, a uniform distribution of light emitted from
the aperture 1108, and a uniform distribution of light reflected
back to the aperture 1108 is achieved.
[0166] Referring next to FIG. 20, a cross-sectional view of a first
fiberoptic bundle 1702 is shown with individual fiberoptic elements
2002 selected to effect the sigmoidal distribution of FIG. 19. As
can be seen, 13 individual fiberoptic elements are present in the
fiberoptic bundle 1702, which is the same number of fiberoptic
conductor ends 1902, 1904, 1906 depicted in FIG. 19 for each of the
three fiberoptic bundles 1702, 1704, 1706. The fiberoptic bundle
1702 shown in FIG. 17 carries the light from the first light
emitting diode to the aperture 1108 of the reader head 706.
Cross-sectional views of the second and third fiberoptic bundles
are similar to that shown in FIG. 20.
[0167] Referring next to FIGS. 21, 22 and 23, three schematic views
are shown illustrating a process for reading test results from
immunoassay test strip 100 with the control region 2102 and the
detection region 2104 depicted thereon. In the example shown, blue
latex particles are detected in the test region and the control
region on a nitrocellulose support. Also depicted are the aperture
1108 of the reader head 706 in a dark reading mode (FIG. 21), a
first light reading mode (FIG. 22) and a second light reading mode
(FIG. 23).
[0168] The reader head assembly (described above) includes the
first light-emitting diode (which in the present example is a blue
LED), the second LED (which in the present example is an amber
LED), a silicon photodiode detector, and fiberoptic fibers arranged
with fiberoptic conductor ends 1902, 1904, 1906 in the sigmoidal
distribution in the aperture 1108 (0.002 inches wide), which is
located at the bottom (or tip) of the reader head 706 at a point
nearest the immunoassay test strip, when the immunoassay device is
inserted into the immunoassay reader device. It is understood that
the selection of LEDs will be dependent upon the signal produced in
the test; all detectable electromagnetic wavelengths, preferably
visible light, are contemplated herein. Fluorescence and other such
labeling means also are contemplated herein.
[0169] The blue LED and the amber LED emit light of specified
wavelengths (.lamda..sub.1 and .lamda..sub.2, respectively). It
should be understood that any suitable wavelengths may be selected.
Such selection is dependent on the particular assay with which the
immunoassay reader device is being employed. The wavelengths
selected are selected so as to allow removal of effects of the
background of the immunoassay test strip or symbology, e.g., bar
code, from the reflectance readings, and to optimize a reading of a
reduction in reflectance associated with accumulated label at the
reaction regions of the immunoassay test strip.
[0170] In a preferred embodiment, where blue latex particles are
detected on a nitrocellulose support, light having a wavelength of
430 nm (blue) is emitted from the first light emitting diode
(LED.sub.1), i.e., the blue LED, into the first fiberoptic bundle
1702. The same wavelengths can be used to read a symbology, such as
a bar code, associated with the assay device. The first fiberoptic
bundle 1702 transmits blue light to the aperture 1108 in the reader
head 706 where it is emitted at an orientation normal to a plane at
the upper surface of the symbology (exemplified bar code) or test
strip. A second light emitting diode (LED.sub.2), i.e., the amber
LED, emits light with a wavelength of 595 nm (amber) into a second
fiberoptic bundle 1704. The second fiberoptic bundle 1704 transmits
the amber light to the aperture in the reader head 706 where it is
emitted at an orientation normal to the plane at the upper surface
of the bar code or test strip.
[0171] At the aperture, individual fiberoptic conductor ends 1902,
1904 of the first and second fiberoptic bundles 1702, 1704, along
with individual fiberoptic conductor ends 1906 from the third
fiberoptic bundle 1706 are arranged in three groups of thirteen
optical fibers each: the first group from the first fiberoptic
bundle 1702, which transmits light emitted by the blue LED to the
aperture 1108; the second group from the second fiberoptic bundle
1704, which transmits light emitted by the amber LED to the
aperture 1108; and the third group, which transmits reflected light
received at the aperture 1108 through the third fiberoptic bundle
1706 to the photodetector. The thirty-nine fibers (thirteen in each
of three groups) each include respective fiberoptic conductor ends
1902, 1904, 1906 arranged in the sigmoidal distribution (or
pattern) (see FIG. 19) at the aperture 1108 such that the
fiberoptic conductor ends 1902, 1904, 1906 are co-planar at the
aperture and in the plane parallel to the plane at the upper
surface of the bar code or test strip, when the reader head 706 is
positioned to take measurements from the bar code or test strip
100.
[0172] At the fiberoptic conductor ends 1902, 1904, 1906, each
fiberoptic fiber (or conductor) has a longitudinal axis that is
normal to the plane at the upper surface of the bar code or test
strip. As a result, light emitted from the fiberoptic conductor
ends 1902, 1904, 1906 is directed in a direction substantially
normal to this surface plane. The fiberoptic fibers in each of the
three groups are arranged along with fiberoptic fibers from the
remaining groups in a sigmoidal (or "S"-like) pattern with three
columns of thirteen fibers each.
[0173] When the immunoassay device is inserted into the cassette
slot at the front of the immunoassay reader device 600, the reader
head 706 is positioned directly over the bar code or test opening
of the assay device such that the longitudinal axes of the optical
fibers at their ends 1902, 1904, 1906 at the aperture, are normal
to a plane at the surface of the immunoassay test strip and the
ends 1902, 1904, 1906 of the fibers at a distance of about 0.010
inches. Light from the first LED and the second LED is transmitted
by the fibers onto the bar code or assay test strip at an angle
normal to the upper surface of the immunoassay device, and light is
reflected normally back from the strip to the ends 1902, 1904,
1906. This reflected light is transmitted by the fibers of the
third fiberoptic bundle to the photodetector.
[0174] The reader head 706 takes three separate reflectance
readings (FIGS. 21, 22 and 23, respectively) from each position at
which it reads of the immunoassay test strip. Such measurements are
made by reading an output of the photodetector (which is a voltage)
while controlling the first and second LED's.
[0175] The first reading is used to determine an amount of ambient
(or background) light leaking into the immunoassay device (e.g.,
light leaking through the cassette slot entrance, or light
reflected/transmitted into the reader through the housing of the
immunoassay device, which may be, for example, white plastic. The
first reading is a "dark" reading taken with the blue LED and the
amber LED both turned off. This dark reading (which is a voltage at
the photodetector) is digitized in a conventional manner using an
analog to digital converter, and may be subtracted by the
processing unit from other "light" readings made in response to
blue LED illumination and amber LED illumination so as to correct
for this light leakage.
[0176] The second reading, used to determine levels of light
reflections associated with the background of the bar code or the
assay test strip itself, is taken with the blue LED pulsed on and
the amber LED turned off.
[0177] The third reading, used to detect the bar code or the
presence of the label on the assay test strip is taken with the
amber LED pulsed on and the blue LED turned off.
[0178] A control circuit (including the processing unit, which
includes a processor, such as a microprocessor) receives the
digitized output of the photodetector for all three readings,
controls the on and off operation of the blue LED and the amber
LED, controls when photodetection readings are taken, and controls
the position of the reader head 706 by controlling the stepper
motor. A memory circuit stores raw and/or processed data (i.e.,
readings from the photodetector). The data also may be displayed to
the operator via the LCD display of the immunoassay reader device
600.
[0179] After being positioned above the housing, the reader head
706 is moved (scanned) across the bar code and/or test strip by the
stepper motor under the control of the control circuit to allow the
reader head 706 to scan the exposed surface of the bar code and/or
assay test strip (including the detection and control zones through
the test window 214 in the immunoassay device). As stated above, in
a preferred embodiment, the distance between reader head 706 and
the bar code or assay test strip 200 is approximately 0.010.''
[0180] The reader head 706 is slidably connected to a rail (e.g.,
guide rods), and is coupled to a worm or screw gear driven by the
stepper motor.
[0181] Under the control of the control circuit, the stepper motor
drives the reader head 706 along the rail in small steps. At each
step, the control circuit takes the three readings described above
("dark", blue LED illuminated, amber LED illuminated). The control
circuit moves the reader head 706 such that the fiberoptic
conductor ends 1902, 1904, 1906 pass directly above and normal to
the exposed surface of the bar code and/or test strip in a sequence
of small steps. As explained above, during each step a sequence of
"dark", blue LED and amber LED readings are taken and recorded.
[0182] The raw data read from the photodetector is then processed
by the control circuit to discern the symbology, such as a bar code
pattern, in order to provide information regarding the assay device
and/or test run and/or reagents, and/or patient and/or to read the
test strip to determine the presence or concentration of analyte in
the sample.
[0183] In a preferred embodiment, when reading the test strip,
since the detection and control latex stripes are each about
0.020'' wide, and since each step of the sensing head is about
0.002'' long, there will be about 10 steps within each stripe,
i.e., within the test region and the control region. Thus, there
will be 10 sets of three readings (i.e., dark, blue LED and amber
LED) at the test region and 10 sets of three readings (i.e., dark,
blue LED and amber LED) at the control region. The remainder of the
reading sets will not be made over either the test region or the
control region.
[0184] In a preferred embodiment, when the assay device is inserted
into the cassette slot of the reader device 600, the reader head
706 is positioned over the bar code or test strip, and the control
circuit then moves the head to an initial (or home) position. The
control circuit moves (scans) the head across the exposed surface
of the bar code or test strip, including the test region and the
control region of the strip, in small increments. At each step, the
control circuit takes the first reading (FIG. 21) of the
photodetector output with the blue LED and the amber LED, both off,
takes the second reading (FIG. 22) with the blue LED pulsed on and
the amber LED off, and takes a third reading (FIG. 23) with the
blue LED off and the amber LED pulsed on. The control circuit then
steps the reader head 706 by controlling the stepper motor and
repeats the three readings at its new location. For the test strip,
this process is repeated for each of 226 steps (0.452'' at
0.002''/step) until the surface of the assay test strip is read.
Where a bar code is read, the length of the bar code is typically
approximately 1 inch in length, and a step size of approximately
0.002-0.008 inches are used; thus between approximately 125-500
steps are performed.
[0185] The raw reflectance data is then analyzed by the control
circuit in accordance with appropriate software control to identify
the symbology, such as a bar code or determine the presence or
concentration of the analyte in the sample. Where the reader is
used to read a bar code associated with the test device, the data
collected from the bar code are transformed into integrated peak
information and analyzed as alphanumeric characters to provide
information about the assay device and/or test run. Where the
reader is used to detect an analyte, the data collected from the
test strip are compared to a threshold or reference reflectance
value to determine the presence or concentration of the analyte.
The output can be displayed via an operator interface, or can be
output to another computer or apparatus.
Data Analysis and Decision Support Systems
[0186] The systems herein include software for data analysis. Data
analysis includes any algorithms or methodology for obtaining
diagnostically relevant information from the raw data. Simple
algorithms as well as decision-support systems, particularly neural
networks are contemplated herein.
[0187] In particular embodiments, the data analysis methodology
includes, some or all of the following steps: (1) optionally
correcting the reflectance readings to correct for light leakage;
(2) reducing the raw reflectance data by using a ratiometric
formula; (3) generating an image of the test data by plotting the
reduced data; (4) expressing this image as a polynomial
mathematical function, for example, by using a combination of a
flat or parabolic image to represent the baseline and two gaussian
curves to represent the peaks; (5) using a curve-fitting algorithm
to generate parameters to define the image; (6) optimizing the
reconstruction of the image and producing a fitted image; (7)
comparing the scanned image and fitted image by solving the linear
regression through the curves; (8) validating the parameters
obtained from the curve-fitting and the peak heights obtained; and
(9) classifying the validated result as positive or negative by
comparing peak heights of a clinical sample to reference samples.
The method may further include: (10) using the test result with
other patient information in a decision-support system to generate
a medical diagnosis or risk assessment.
[0188] In alternative embodiments, the parameters used to define
the image, as in (5) above, and to classify the sample, as in (9)
above, can be generated using trained neural networks.
Data Reduction
[0189] In an exemplary embodiment, the raw reflectance data
obtained from the instrument are stored as an array of points
containing a number of rows (n) corresponding to the number of
points at which readings were taken along the test strip, and a
number of columns (m) corresponding to the reflectance readings
taken at each point, including background or dark readings and
readings at different wavelengths. If necessary, the reflectance
readings are processed by first subtracting the dark reading taken
at the corresponding step to correct for light leakage, which
typically is negligible. The corrected reflectance readings are
then input into a ratiometric algorithm, which removes noise from
the membrane and normalizes data between test strips:
f(y)=[(R.sub..lamda.1/R.sub.max/.lamda.1*R.sub.max/.lamda.2/R.sub..lamda.-
2)].
[0190] The algorithm is based upon the ratio of readings at the
different wavelengths and calculates a reduced data set
(1.times.n), which is used to generate a curve from the original
reflectance data. In processing the data, a new column of reduced
data is generated by using the ratiometric formula.
[0191] When reading an assay test strip, as described above, the
size of the matrix is 4.times.226, where 4 is the number of columns
of data collected and 226 is the number of steps, or readings,
taken along the test strip. The first column contains information
about the location on the test strip from which the data is
obtained; the second column is the reflectance in the absence of
illumination by the instrument (dark reading); the third column is
the reflectance when the test strip is illuminated at the first
wavelength (e.g. 430 nm); and the fourth column is the reflectance
when the test strip is illuminated at the second wavelength (e.g.
595 nm). The information in the second column is usually zero,
unless a light breach has occurred with the instrument. The
reflectance values in the third and fourth column are preferably in
the 3,000-24,000 range.
[0192] Where a bar code is read, between approximately 125-500
steps are performed in reading the bar code, therefore, the matrix
size would be between 4.times.125 and 4.times.500.
[0193] In the preferred embodiment described herein, the
ratiometric formula would read as follows: f(y)=[(R.sub.430
nm/R.sub.max/430 nm*R.sub.max/595 nm/R.sub.595 nm)]-1.
[0194] The algorithm calculates a reflectance ratio for each step,
generating a fifth column of data. The information contained in the
first, third and fourth columns can be converted into an image by
plotting the first column (x-value) against the fifth column
(y-value). Thus, the original data array has been converted to a
2-dimensional image, or an array of the size 1.times.226. The
reflectance ratio is then plotted as a function of each step. In
reading an assay test strip, as described above, the result is a
two-peak graph with the peaks occurring at the two stripes,
corresponding to the detection and control zones. The reflectance
data may then be further processed to obtain an accurate
determination of analyte concentration in the patient sample.
[0195] Where a bar code is read, a graph is produced that
corresponds to the reflectance pattern of the bar code. Pattern
matching is then performed using any of a number of methods
commonly known to those of skill in the art in order to identify
the bar code and associate it with the particular assay run.
[0196] Generating and Validating Images
[0197] The image created by a plot of the data obtained from
reading an assay test strip, as described above, has three basic
components: a baseline or background that is either flat or
parabolic; a peak corresponding to the detection zone that is
gaussian; and another peak corresponding to a control zone that
also is gaussian.
[0198] The parabolic component can be defined using 3 variables:
f(y)=Ax.sup.2+Bx+C.
[0199] Each of the gaussian curves can be defined using 3
variables:
f(y)=Area*[exp.sup.-(x-.mu.)(x-.mu.)/2.sigma.*.sigma.]/(.sigma.(2.pi.).su-
p.1/2) [0200] where Area=area contained within the gaussian; [0201]
.mu.=x-value of center position; and [0202] .sigma.=width.
[0203] A second plot can be generated from the three component
curves, using 9 variables. This process is accomplished using a
curve-fit algorithm. Any such algorithm known in the art may be
used. Alternatively, the 9 parameters may be obtained using neural
networks, as described below. From the parameters generated from
the curve-fit function, a showfit function is used to generate an
image from the fitted data. For example, in the preferred
embodiment, a showfit function is used to generate a 1.times.226
matrix representing the fitted curve defined by the 9
parameters.
[0204] The fitted image is then compared to the original scanned
image, which is produced by plotting the 1.times.226 data points as
discussed above, to measure the performance of the curve-fit
function. This is accomplished by plotting the fitted image against
the scanned image and solving the linear regression through these
values. The fitted image is then compared to the original image by
plotting the fitted image against the scanned image and solving the
linear regression through the values, where an exact match would
yield a line with slope=1 and r.sup.2=1).
[0205] Once the curves have been fitted, the peak height of the
curve in the detection zone is determined by subtracting the
parabolic baseline from the maximum peak height. The peak height is
then compared to that of a previously run sample of known analyte
concentration. If the peak height of the clinical sample is greater
that the peak height of the reference sample, then the test result
is positive. If not, a negative test result is returned. The peak
height of the curve representing the control zone also may be
checked to determine if it meets a required minimum height, in
order to test that the system is functioning.
[0206] Alternatively, peak areas may be calculated and compared to
give a determination of analyte concentration in the sample. The
graph may be mathematically analyzed, with a sigmoidal calculation
across the background and a gaussian calculation to integrate the
area beneath each of the two peaks. The analyte concentration is
then determined based upon the ratio of the integrated area beneath
each of the two peaks.
[0207] Methods for Reducing the Image to Parameters
[0208] Images or large sets of data, are not readily amenable for
developing and training neural net analyses. For large data sets,
the number of inputs required for neural network training must be
reduced. To do this assumptions regarding the types of data that
can be omitted are made. As a result of the loss of information,
the performance of subsequently trained neural nets will hinge on
the validity of the assumptions made. A method for reduction of
data that reduces dimensionality with minimal or no loss of
information will avoid this problem. The reduced database can be
validated by using it to reconstruct the original dataset. With
minimal or no loss of information, subsequently trained networks
should yield higher performance than networks that are trained with
less complete data. Methods are provided herein for reducing
dimensionality with minimal loss of information. These methods are
directly applicable to the images that are generated and data
generated from the test strips described herein and also is
generally applicable to all images and large datasets.
[0209] Methods for Optimizing the Reconstructed Image
[0210] Parameters for a mathematical function designed to
reproduce, or approximate the scanned image are effective at
determining the concentration of the compound being tested and
thereby providing a means to classify the sample being tested.
Examination of the data, for example, from the fFN test provided
herein demonstrates that a scanned image can be constructed from
three basic elements. There is a background density, referred to
herein as the baseline density. Superimposed on the baseline are
the two peaks. The first peak is referred to as the control peak
and the second is the test peak. Since the shape of these peaks is
very similar to a normal curve, it was assumed that the peaks have
a gaussian shape. One characteristic of the "normal curve" that can
be exploited is that the area under the curve is always 1.0. By
modifying the formula, the height of a peak can be determined from
a single function parameter.
[0211] When analyzing an image, the peak density function used is:
Peak Density=Height*EXP(-Z*Z) [0212] where Z=(X-Pos)*S, [0213]
X=Pixel Number, [0214] Pos=Pixel number of center of peak, [0215]
S=Spread or width of the peak, and [0216] Height=Height of the
peak. This function contains three parameters, Height, S and Pos.
When the three parameters are set correctly, this function will
closely match one of the peaks in the test strip image. With two
peaks in the image, this function also can be used to estimate the
second peak. With two peaks, there are six parameters so far that
must be optimized. The goal of the optimization will be to change
the above parameters in such a way as to reconstruct the image as
closely as possible.
[0217] In order to reconstruct the image completely, the baseline
of the image must also be estimated. Examination of scanned images
showed that the baseline had a slight curve. By using a parabolic
or quadratic form function, the baseline density is estimated. The
function for the base density is, Base
Density=X*X*Curve+X*Slope+Offset. Thus, the image can be accurately
reconstructed by combining these three function in the following
summation, Image Density=Base Density+Control Peak Density+Test
Peak Density. This results in a total of nine parameters that must
be optimized for an accurate reconstruction of the image.
[0218] The basic problem with attempting to fit this complex
function to the test strip image is that there are no simple means
for finding the optimal values for function parameters as there are
for linear regression. There are many numerical techniques that can
be used to optimize the parameters of the above image density
function. The one used here is the downhill simplex method (see,
"Numerical Recipes in C," Second Edition, Cambridge University
Press, 1992).
[0219] The basic method of this optimization uses an iterative
approach to optimize the function parameters based on a defined
cost function. Here the cost function is defined as the sum of the
squares of the differences between the original image and the
reconstructed image for every pixel in the scanned image. The
downhill simplex method uses a simplex to accomplish this
optimization. A simplex is a geometrical figure in N dimensions
containing N+1 points. For the image density function defined
above, N has the value 9. In two dimensions, for example, a simplex
will contain 3 points, with lines connecting each pair of points.
This simplex is called a triangle. As the dimension increases, the
complexity of the simplex also increases. In three dimensions a
simplex is a tetrahedron. This implies that if there are N
parameters to be optimized, then N+1 solutions must be maintained.
This translates to N.sup.2+N storage locations that are required to
run the algorithm.
[0220] For exemplification, the optimization problem with 2
parameters is as follows. The simplex, a triangle, is formed from
three points or three different sets of values for the parameters.
These three points (call them solutions A, B and C), which are
generated in the following way. Starting with and initial set of
parameters (solution A), each parameter is perturbed by a small
amount (typically 0.01). When the first of the two parameters is
changed, solution B is generated. When the second parameter is
perturbed, solution C is generated. The three solutions must be
evaluated to determine the error function value for each.
[0221] Suppose that solution A has the highest error function
value. The simplex algorithm attempts to make an improvement by
picking a new point (solution, or set of parameters), that lowers
the error function value. This basic operation is called a
reflection. Three attempts are made at improving the solution. The
first, normal, reflection picks its new set of parameters by
forming a line from point A to the average of the remaining points.
The line is then extended through the average point an equal
distance. This new point is the reflection point. Reflection is the
correct term since if one were to place a mirror on the line
between B and C, the new point corresponds exactly to the
reflection of A in the mirror.
[0222] If the new error function value for the normal reflection is
better than the best current solution, then an expansion reflection
is attempted. In this case the line from A is extended by the Step
Up Factor (typically 1.50) through the average point. This
operation makes the simplex larger. The point that gave the best
error function value (either the normal reflection of A or the
Expansion reflection of A) is retained as the new A point.
[0223] If the new error function value for the normal reflection is
still the worst solution, then a contraction reflection is
attempted. In this case the line from A is extended by the Step
Down Factor (typically 0.75) through the average point. This
operation makes the simplex smaller. If this solution is better
than the original error function value for point A, the reflection
point is retained as point A. If no improvement is made in the A
solution, then the entire simples is contracted by moving each
point toward the point with the best error function value by the
fraction specified by the Shrink Factor (typically 0.95). These
reflection operations continue until the difference between the
best and worst solutions falls below the Restart Tolerance
(typically 1.0E-9).
Alternative Method 1 for Reducing the Image to Parameters Using a
Neural Network
[0224] A neural network can be used as an alternative to a
polynomial mathematical function for the purpose of generating
parameters that can be used to reconstruct an image. The basic
architecture of the neural network contains at least three
processing layers. During the training process, a sequence of
example images are presented to the network for training. Training
continues so that the error between each image and its
reconstruction is minimized across the set of images used for
training. The image, or a subsection of the image, is presented to
the input layer of the network. The middle layer, or hidden layer,
of the network contains a number of processing element that is much
smaller then the number of inputs in the input layer. The output
layer contains the same number of processing elements as the input
layer. The output layer of the network will represent the
reconstructed image that is presented to the input layer.
[0225] An alternative architecture contains an odd number of hidden
layers, with the middle hidden layer containing a much smaller
number of processing elements than the input and output layers. In
each layer of the network, each processing element is connected to
each of the processing element outputs of the previous layer.
[0226] The processing element used in the network typically
generates a weighted sum of the inputs to processing element, with
a transfer function applied to the weighted sum to generate the
output of the processing element. The transfer function is any such
function normally used in a neural network, including the sigmoid
function, or the hyperbolic tangent function.
[0227] The neural network can be trained using any standard neural
network training rule, including the back propagation learning
rule. At each step of the training process, a training image is
presented to the inputs of the neural network. The same image also
is be presented to the outputs of the network as the desired, or
target, output of the network. As learning proceeds, the error
between the outputs of the neural network and the desired outputs
of the network decreases.
[0228] In order for the error to decrease, the neural network
middle hidden layer generates a greatly reduced representation of
the input image that contains enough information to reconstruct the
image. This reduced representation therefore also contains the
information needed to classify the image.
[0229] Once trained, a new image is presented to the inputs of the
neural network. The outputs of the middle hidden layer are then be
used as the inputs to the classification means for further
processing.
Alternative Method 2 for Reducing the Image to Parameters Using a
Neural Network
[0230] A second alternative method for reducing an image to useful
parameters is to substitute the neural network directly in place of
the polynomial mathematical function. Here, the inputs of the
neural network are the coordinates of the pixel in the image being
examined. The desired output of the network are the density value
of the associated pixel.
[0231] The architecture of this neural network is substantially
smaller then the architecture described in the first alternative
method. Here the weights of the neural network become the
parameters to be used by the classifier. The types of processing
elements used in this architecture include the radial basis
function type, and provisions might be made to allow a mix of
processing element types in the hidden layer of the neural network.
The architecture is developed to provide the smallest possible
number of weights while still being capable of reconstructing the
image.
[0232] In this alternative, the neural network is trained only on
the image under consideration. Thus, each time a sample is tested,
the network would be retrained. The weights of the trained network
are used as inputs to the classification means.
[0233] Validation Method for Classifying the Image from the
Parameters
[0234] Once the parameters are estimated, the parameters generated
from the image reconstruction process along with several parameters
easily calculated from the scanned image are used to classify the
sample. In addition, the image parameters from several reference
scans were used. The process of classification incorporates two
steps. The first is a validation step to determine if the sample
under consideration should be rejected or classified. The validated
result is then classified as positive or negative as described
above.
[0235] To ensure the accuracy of a test result, the system
producing that result should be validated. Validation protocols are
used to confirm that all components of a system operate properly,
and that the data received from the system is meaningful. Moreover,
in systems where raw data from instruments are manipulated by
software, the proper functioning of that software should also be
validated.
[0236] Validation of data analysis software can be performed in any
number of ways. Typically, a known sample (e.g., reference,
positive control, negative control) can be tested in the system to
validate that the expected result is obtained. Alternatively, known
raw data can be stored in memory and acted upon by the data
analysis software to validate that the expected result is obtained.
Such validation protocols ensure that the software is operating
properly before a clinical sample of interest is evaluated by that
system.
[0237] Validation of test systems also can be performed during the
evaluation of a clinical sample being tested by that system. These
types of validation protocols can evaluate components of the
system, either individually or together. When the criteria set by
validation protocols are not achieved, an invalid result is
obtained, and the user will be made aware of the system
malfunction. Such processes ensure that only accurate test results
are presented to the user.
[0238] In an exemplary embodiment, for example, data are validated
by several methods. First, the data are checked for completeness by
checking that the size of the matrix is m.times.n, where m is the
number of columns of data collected (e.g., location on dipstick,
dark reading, reflectance at .lamda..sub.1 and reflectance at
.lamda..sub.2) and n is the number of steps, or readings, taken
along the test strip. For example, in the preferred embodiment, the
matrix must be of an exact size of 4.times.226.
[0239] Next, the maximum peak heights must meet certain minimum
values or the test data are invalid. For example, if the sample in
question is a fFN positive reference (i.e. about 50 ng/ml of fFN)
in the fFN point of care test (POCT), then the maximum control peak
height must be between 0.200 and 1.500 units (inclusive) and the
maximum test peak height must be between 0.020 and 0.310 units
(inclusive) or the result is invalid.
[0240] If the sample in question is a fFN POCT positive control,
then the maximum test peak height of the positive control (i.e, a
control sample that always yields a positive result, typically
about 70 to 80 ng/ml for the fFN POCT) must be greater than the
maximum test peak height of the positive reference, or the result
is invalid.
[0241] If the sample in question is a negative control (i.e.,
always yields a negative result, which for the fFN POCT is about
10-15 ng/ml), then the maximum test peak height of the negative
control must be less than the maximum test peak height of the
positive reference, or the result is invalid.
[0242] A run is only valid when the results of the fFN positive
reference, positive control and negative control are all valid.
[0243] If the sample in question is a clinical sample, then the
maximum control test peak height must be greater than about 0.20
units, or the result for that sample is invalid. Note, however,
that the run may remain valid.
[0244] For comparison of the fitted image and the scanned image by
solving the linear regression, the slope must be between 0.99 and
1.10, or the result is invalid. If the sample is a positive
reference, positive control or negative control, then the run is
invalid. If the sample is a clinical sample, then the run remains
valid. The value of r.sup.2 must be greater than 0.78, or the
result is invalid. If the sample is a positive reference, positive
control or negative control, then the run is invalid. If the sample
is a clinical sample, the run remains valid.
[0245] For a valid result and valid run, if the maximum peak height
of the clinical sample is greater than or equal to the maximum peak
height of the positive reference, the test result is positive. If
the maximum peak height of the clinical sample is less than the
maximum peak height of a negative reference, the result is
negative.
[0246] Thus, the validated result is then classified as positive or
negative as follows: [0247] a) for a valid result and valid run, if
maximum peak height of clinical sample is greater than or equal to
maximum peak height of fFN positive reference, the result is
positive. [0248] b) for a valid result and valid run, if maximum
peak height of clinical sample is less than maximum peak height of
fFN negative reference, the result is negative.
[0249] Alternatively, instead of calculating height, the areas
under the curves can be compared. The same data are obtained, if
the area under the curve from a clinical sample is compared to the
area under the curve of the 50 ng/ml reference sample.
Alternative Method for Classifying the Image Using a Neural
Network
[0250] Based on the available data generated from scans all
possible variables were identified that could be used to improve
the ability to classify the sample. The initial training runs used
the parameters generated from the image reconstruction process
along with several parameters easily calculated from the scanned
image. One such parameter is the area under a peak. It can be
calculated from original parameters as following: [0251]
Area=sqrt(n)*Height/S, where S is spread or width of the peak. A
sigma variable, related to the normal distribution also can be
calculated from the parameters by: Sigma=1/(sqrt(2)*S). In
addition, the image parameters from a Calibrator scan (fFN positive
reference) were also used. The following is a list of the variables
that are available for use by the neural network. [0252] 1. Sample
Baseline Square Term [0253] 2. Sample Baseline Linear Term [0254]
3. Sample Baseline Offset [0255] 4. Sample Control Peak Position
[0256] 5. Sample Control Peak Sigma [0257] 6. Sample Control Peak
Area [0258] 7. Sample Test Peak Position [0259] 8. Sample Test Peak
Sigma [0260] 9. Sample Test Peak Area [0261] 10. Sample Test Peak
Height [0262] 11. Sample Control Peak Height [0263] 12. Sample
Baseline estimated value between the peaks [0264] 13. Sample Ratio
of Test Area to Control Area [0265] 14. Sample Ratio of Test Height
to Control Height [0266] 15. Calibrator Baseline Square Term [0267]
16. Calibrator Baseline Linear Term [0268] 17. Calibrator Baseline
Offset [0269] 18. Calibrator Control Peak Position [0270] 19.
Calibrator Control Peak Sigma [0271] 20. Calibrator Control Peak
Area [0272] 21. Calibrator Test Peak Position [0273] 22. Calibrator
Test Peak Sigma [0274] 23. Calibrator Test Peak Area [0275] 24.
Calibrator Test Peak Height [0276] 25. Calibrator Control Peak
Height [0277] 26. Calibrator Baseline estimated value between the
peaks [0278] 27. Calibrator Ratio of Test Area to Control Area
[0279] 28. Calibrator Ratio of Test Height to Control Height Four
predictor variables were also added. In these variables the
calibrator strip value is compared to the sample strip value and a
+1 or -1 is used depending on the comparison. The additional
variables are: [0280] Test Area Predictor [0281] Area Ratio
Predictor [0282] Test Height Predictor [0283] Height Ratio
Predictor. The desired, or target output of the neural network was
a classification of the concentration of the sample. If the sample
concentration was greater than or equal to 50 ng/ml the desired
output was set to 1.0. The desired output was set to 0 otherwise. A
sensitivity analysis of the associated training runs was used to
indicate which variables were important to the prediction task. The
ThinksPro software product from Logical Designs Consulting was used
to train the networks and perform the sensitivity analysis.
Alternatively, a variable selection process based on genetic
algorithms or some other method could be used to select the best
subset of variables from this list (see, e.g., copending U.S.
application Ser. Nos. 08/798,306 and 08/912,133, which describe a
suitable variable selection process).
[0284] Using the reduced set of variables one or more networks are
trained to estimate the classification of the sample. If more than
one network is used, the outputs of each network are averaged
together to give a consensus result.
[0285] In another embodiment, the nine variables may optionally be
fed through a previously trained neural network to obtain a test
result. For example, the nets may be trained with data for which
ELISA test results are known. Alternatively, variables other than
the nine described above may be used to train the neural net. The
nets can be used not only to return positive or negative results,
but also to determine if the assay itself is valid for any
particular run.
[0286] The reduction of data for input to neural networks can be
accomplished by a neural network itself. An example of such a net
is a net with an hourglass architecture with an input, output and
three hidden layers, wherein the input and output layers contain n
nodes, with the first and third hidden layers containing less than
n nodes, and the second hidden layer containing five nodes. If
trained so that the output layer exactly matches the input layer,
such nets would reduce the original dataset of n elements down to
five elements, and also retain the ability to reconstruct the
original dataset of n elements from these five elements.
[0287] Further Analysis Using Decision Support Systems
[0288] The output from the data analysis step provides an
assessment of the raw biochemical test data that is measured by the
reader or other instrument. Such data may then be considered as is,
but is can be further entered into a decision-support system,
particularly a neural network, that has been trained to evaluate
the particular data and disease. For example, U.S. application Ser.
No. 08/599,275, now abandoned, copending U.S. application Ser. No.
08/798,306, and copending U.S. application Ser. No. 08/912,133,
filed Aug. 14, 1997, as well as published International PCT
application No. WO 97/29447, which claims priority to U.S.
application Ser. No. 08/599,275, filed Feb. 9, 1996, now abandoned,
and copending U.S. application Ser. No. 08/798,306 and corresponds
to U.S. application Ser. No. 08/912,133 describe neural nets and
methods for developing neural networks for diagnosis of disorders.
The accuracy of biochemical test data is improved when used in
these neural nets. Such neural nets, are thus contemplated for
inclusion in the systems herein.
[0289] Briefly, in the methods described in these applications
patient data or information, typically patient history or clinical
data, are analyzed by the decision-support systems to identify
important or relevant variables and decision-support systems are
trained on the patient data. Patient data are augmented by
biochemical test data or results to refine performance. The
resulting decision-support systems are employed to evaluate
specific observation values and test data to guide the development
of biochemical or other diagnostic tests, to assess a course of
treatment, to identify new diagnostic tests and disease markers, to
identify useful therapies, and to provide the decision-support
functionality for the test. Methods for identification of important
input variables for medical diagnostic tests for use in training
the decision-support systems to guide the development of the tests,
for improving the sensitivity and specificity of such tests, and
for selecting diagnostic tests that improve overall diagnosis of,
or potential for, a disease state and that permit the effectiveness
of a selected therapeutic protocol to be assessed also are
provided. The methods for identification can be applied in any
field in which statistics are used to determine outcomes. A method
for evaluating the effectiveness of any given diagnostic test also
is provided.
[0290] Thus, such neural networks or other decision-support systems
will be included in the systems provided herein as a means of
improving performance of the biochemical test data.
[0291] The following examples are included for illustrative
purposes only and are not intended to limit the scope of the
invention.
EXAMPLE 1
Immunoassay Test Strip
[0292] A. The Test Strip
[0293] The test strip 100 includes a membrane system including
three components: a porous or bibulous member 102; a conjugate pad
108; and an absorbent pad 110. The membrane system may be mounted
on a substrate or backing 112, with the conjugate pad 108 and the
absorbent pad 110 slightly overlapping the porous or bibulous
member 102, which is interposed therein between. As can be seen in
FIGS. 1A and 1B, the conjugate pad 108 overlaps the porous or
bibulous member 102 so that a fluid sample placed onto the
conjugate pad 108 is communicated from the conjugate pad 108 to the
porous or bibulous member 102. Similarly, the absorbent pad 110
overlaps with the porous or bibulous member 102 so that fluid
samples introduced into the porous or bibulous member 102 from the
conjugate pad 108 can then be transmitted to the absorbent pad 110.
Thus, the conjugate pad 108, the absorbent pad 110 and the porous
or bibulous member 102 are all in fluid communication with one
another, making any fluid sample placed on the conjugate pad 108
able to propagate through the conjugate pad 108 to the porous or
bibulous member 102 and then to the absorbent pad 110.
[0294] The porous or bibulous member is capable of transporting a
liquid sample along the test strip and serves as the solid support
upon which the immunoreactions occur. Antibodies which react with
the target analyte and/or label are immobilized on the solid
support. Possible solid supports include paper and cellulose
derivatives, such as cellulose esters and ethers, natural and
synthetic polymeric materials, such as vinyl polymers and partially
hydrolyzed derivatives, polycondensates, copolymers and inorganic
materials. A preferred solid support is a nitrocellulose
membrane.
[0295] The porous or bibulous member contains two distinct zones, a
detection zone 104 and a control zone 106, at which two different
antibodies are immobilized. The detection zone contains an
immobilized capture antibody that binds the analyte of interest,
whereas the control zone contains an immobilized antibody or other
component, such as an antigen, that binds labeled antibody
conjugate (discussed below) which has not bound to analyte.
[0296] The membrane system also includes a conjugate pad 108, which
serves as a sample application component, and which includes an
antibody to the analyte, which is conjugated to a detectable label.
The conjugate pad is in fluid communication with the porous or
bibulous member 102. The labeled antibody conjugate is diffusively
bound to the conjugate pad and becomes mobile upon application of
the liquid sample and moves along the test strip. The conjugate pad
is made of a porous material, such as glass fiber. The conjugate
pad also may act as a pre-filter for the sample.
[0297] The membrane system also may include an absorbent pad 110,
which also is in fluid communication with the porous or bibulous
member, and which serves to draw liquid continuously through the
device. The absorbent strip may be made of a material such as
cellulose paper or other material known to those of skill in the
art.
[0298] Referring to FIG. 2A, which depicts an exemplary immunoassay
device 200, including a test strip and housing assembly 200, the
housing 202 generally surrounds the test strip 100 (FIGS. 1A and
1B) and includes an opening through which test sample is applied
204, as well as an aperture above the detection and control zones
206 that permits measurement of the amount of label by the reader,
which is correlated with the amount of analyte in the test sample.
The housing 202 includes at its upper surface 208 a fattened end
210, used for gripping the housing 202, an application window 204
(or sample window) through which a sample is applied to a conjugate
pad 108 of an immunoassay test strip within the housing 202. The
housing 202 also includes a test window 214 through which the test
result of the immunoassay is viewed. In accordance with the
embodiments shown, no window material is mounted within the test
window 214 (or the sample window 212). Thus, an optical path from
outside the housing 202 through the test window 214 to the
immunoassay test strip is unobscured by even a transparent
material. Other alternative embodiments may include an optically
transparent material (transparent at wavelengths emitted by light
emitted from devices described herein), however, such is not
preferred. Also, as shown in FIG. 2A and FIG. 2B, the housing may
include a symbology, exemplified as a bar code 216 or 316 that can
be read by the reader or a separate reading device and associated
with identifying information pertaining to the particular device
and/or test run or other information.
[0299] An alternative embodiment of the test device is shown in
FIG. 2B. The components of device are shown in FIG. 3 and include
the upper and lower members 302 and 304 of the housing and the test
strip 100. Also shown are the sample application port 306, test
window 308, and the optionally included bar code 316.
[0300] Referring next to FIG. 4 a top view is shown of the
immunoassay test strip housing 202 of FIG. 2A. Shown are the sample
window 212, and the test window 214, and the enlarged gripping
portion 210. Also shown are structures 402 for holding the
immunoassay test assembly within the housing 202 and structures 404
for securing upper and lower halves of the housing 202 to one
another.
[0301] Referring next to FIG. 5, a side cross-sectional assembly
view is shown of the housing 202 for the immunoassay test strip
100. Shown are the sample window 212, the test window 214, and the
structures 402 for holding the immunoassay test strip assembly in
place within the housing 202. As can be seen, an upper half 502 of
the housing 202 is mated with a lower half 504 of the housing 202.
The immunoassay test strip is sandwiched between the upper and
lower halves 502 and 504 of the housing 202 and is secured in place
by the structures 402 of the upper half 502. The immunoassay test
strip is positioned so as to be viewable through the test window
214 when the immunoassay test strip assembly is secured within the
housing and the conjugate pad is positioned to be contactable
through the sample window 212.
[0302] These devices are particularly adapted for use with the
reflectance reader provided herein.
[0303] B. Colored Latex Label
[0304] The immunoassay test strip includes a membrane system
supported on a plastic backing. The membrane system is formed from
three partially overlapping materials: a conjugate pad made of
Whatman glass fiber (F075-07S, 2.4 cm length) treated with
polyvinyl alcohol (PVA), a nitrocellulose strip supplied by
Sartorius (8 .mu.m, 3.3 cm length) and an absorbent pad made of
Whatman C7218 (1.65 cm length) cellulose paper. These three
materials are in fluid communication with each other. The conjugate
pad and nitrocellulose overlap by 1 mm and the nitrocellulose and
absorbent pad overlap by 4 mm. The membrane materials are
hand-laminated and attached to a membrane card, which is cut using
an Azco guillotine compression cutter, using G&L adhesive
membrane.
[0305] The conjugate pad contains a mouse monoclonal anti-fFN
antibody (FDC-6 or A137) conjugated to latex particles containing a
blue dye. The conjugate pad acts as a pre-filter for the sample in
that mucous from the sample is left behind in the conjugate pad
after performing the assay.
[0306] The latex particles, which are polymerized from styrene and
acrylic acid, may be any suitable latex particles (such as are
available from Bangs Laboratories). The particles are polymerized
in an aqueous solution with a surfactant added. The particles are
internally labeled with blue dye by swelling the particles in
organic solvent and adding the dye. The particles are then placed
in an aqueous solvent, which shrinks the particles and traps the
dye. The dye is an organic soluble blue dye. Carboxyl groups are
covalently attached to the surface of the bead for coupling to the
antibody. The particles are supplied as a 2.5-10% aqueous
suspension containing surfactant as Bangs Uniform Microsphere Stock
D0004031 CB and have a mean diameter of 0.40 .mu.m, with a standard
deviation of 0.4 .mu.m, and a surface area of 1.405e+13
.mu.M.sup.2/g.
[0307] Antibodies are conjugated to the latex particles in a
one-step covalent conjugation process using EDAC, a carbodiimide
coupling reagent. The conjugate is characterized as 1% solids; 50
.mu.g/mg beads total bound protein (Bead BCA); and >80% covalent
bound protein (Tris-SDS+Bead BCA).
[0308] The antibody conjugated to the latex particles is mouse
monoclonal antibody specific for fetal fibronectin. The antibody
(FDC-6 or A137 monoclonal) is raised against whole molecule
onco-fetal fibronectin from a tumor cell line. The antibody is
produced as ascites at a contract manufacturer and is purified by
Protein G and dialyzed into PBS buffer.
[0309] The nitrocellulose strip contains two distinct zones, a
detection zone and a control zone, at which two different
antibodies are immobilized. The detection zone contains immobilized
anti-fibronectin polyclonal antibody as a capture antibody, whereas
the control zone contains immobilized goat anti-mouse polyclonal
antibody. The anti-fibronectin polyclonal antibody is produced in
goats. The antisera is obtained from a commercial source and is
purified by use of a fibronectin column which is made by attaching
purified fibronectin (antigen) to a resin. The antisera is passed
through a column containing the resin. After washing unbound
material, the antibody is eluted via low pH glycine. The purified
antibody is then dialyzed. The goat anti-mouse IgG antibody (GAMGG)
immobilized in the control zone is obtained from Biosource. The
antibody is purified by passing the serum through a mouse IgG
column, which binds the antibody, and then eluting off the antibody
using glycine.
[0310] The antibodies are applied to the conjugate pad and
nitrocellulose strip using an IVEK Linear Striper, which is a
volumetric ceramic piston pump dispenser. The anti-fibronectin
polyclonal capture antibody is applied in a 1.times. Spotting
Buffer P/N 00387, which contains citrate, phosphate and NaCl, at an
antibody concentration of 1 mg/ml and a striping rate of 1
.mu.l/sec. The position of the test line is 3740 mm from the bottom
of the strip. The control antibody is applied in a 1.times.
Spotting Buffer P/N 00387 at a concentration of 0.5 mg/ml and a
striping rate of 1 .mu.l/sec. The position of the control line is
43-46 mm from the bottom of the strip. The dimensions of the
antibody stripes are approximately 7.5 mm (wide).times.0.5-1.0 mm
(high). The nitrocellulose strip is not otherwise treated after
application of the capture and control antibodies to block
non-specific binding sites.
[0311] The detection and control stripes are applied to the strip
and then dried for 60 minutes at RT, after which the conjugate is
striped onto the strip. The conjugate is mixed in a diluent
containing 20% sucrose, 0.2% BSA, 0.5% TW20 and 100 mm Tris. After
application of the conjugate, the strip is then dried for 30 min.
at 37.degree. C.
[0312] The test strip is contained within a housing, which includes
a lower member and an upper member with openings that include a
circular aperture above the area of the conjugate pad, through
which test sample is applied, and a rectilinear aperture above the
detection and control zones. The circular application aperture is
in contact with the test strip. The latex conjugate is placed
slightly downstream from the sample application opening. The upper
and lower members are mated together to sandwich the test strip.
The test strip is confined non-removably in the housing, and the
device is not intended to be re-usable. The upper member is
configured for use with a reader that measures the amount of label
that is indicative of the amount of fetal fibronectin in the test
sample.
[0313] C. Colloidal Gold Label
[0314] In an alternative embodiment, colloidal gold is used for
labeling the antibody. The test strip configuration is similar to
that described in EXAMPLE 1A for the latex particle embodiment,
with the following modifications.
[0315] In the colloidal gold assay, a goat polyclonal antibody to
human adult and fetal fibronectin is present in the conjugate pad,
immobilized mouse monoclonal anti-fetal fibronectin antibody
(specific to the III CS region of fetal fibronectin) is present in
the detection zone of the nitrocellulose test strip and immobilized
human adult fibronectin is present in the control zone.
[0316] The anti-fibronectin antibodies (polyclonal) are labeled
with colloidal gold by passively adsorbing anti-fibronectin
antibodies onto colloidal gold. This preparation is then treated
with a solution containing protein and polyvinyl pyrrolidone (PVP)
to coat the colloidal gold particles. This method is described in
Geoghegan and Ackerman, Journal of Histochemistry and
Cytochemistry, 25(11):1187-1200 (1977).
EXAMPLE 2
Immunoassay Procedure
[0317] A. Colored Latex Label
[0318] In conducting the assay, the sample is extracted from a swab
into antiprotease transfer buffer (0.05 M Tris buffer, pH 7.4, 1%
BSA, 5 mM EDTA, 1 mM phenylmethylsulfonyl fluoride (PMSF), and 500
Kallikrein Units/ml of Aprotinin), heated for 15 min. at 37.degree.
C. and filtered through a large pore (25.mu.) plunger filter. A
volume of 200 .mu.l of test sample is then delivered to the
conjugate pad at the application zone using a standard plastic
pipet. Any fFN in the sample will bind to the labeled monoclonal
antibody and the resulting complex migrates into the nitrocellulose
strip. When the complex encounters the detection zone, the
immobilized anti-FN antibody binds the complex, thereby forming a
colored stripe due to the aggregation of the dye-containing latex
beads. Any unbound latex-conjugated anti-fFN antibody continues to
migrate into the control zone where it is captured by the
immobilized goat anti-mouse antibody and thereby forms a colored
stripe due to the aggregation of the dye-containing latex beads.
The reaction time is 20 minutes.
[0319] B. Colloidal Gold Label
[0320] The test strip assay procedure is similar to that described
in EXAMPLE 2A for the latex particle embodiment, with the following
modifications. The buffer used to extract the sample is
Tris-acetate and a protein matrix (4% PSA and 4% PVP).
[0321] Fetal fibronectin and adult human fibronectin in the sample
bind with the labeled anti-fibronectin antibody conjugate on the
conjugate pad. The labeled fetal fibronectin-anti-fibronectin
complex and adult human fibronectin-anti-fibronectin complexes, and
unbound labeled anti-fibronectin conjugate migrate into the
nitrocellulose strip, where they encounter the detection region,
including immobilized anti-fetal fibronectin monoclonal
antibody.
[0322] In the detection region, the immobilized anti-fetal
fibronectin capture antibody binds with the fetal
fibronectin-anti-fibronectin complex, whereby a gold label forms a
colored stripe due to the concentration of the gold label. The
amount of gold label bound to the test region correlates with the
amount of fetal fibronectin in the sample.
[0323] The unbound labeled anti-fibronectin antibody conjugate and
adult human fibronectin-anti-fibronectin complex then pass to the
control region of the immunoassay test strip, which includes
immobilized adult human fibronectin. There, any unbound antibody
conjugate binds to the immobilized adult human fibronectin, where
the gold label forms a second colored stripe. The presence of a
colored stripe indicates that the assay results are valid, whereas
the absence of this stripe indicates that the results are not
valid, i.e., that the sample did not reach the control region, and
thus a good reading at the test region cannot be assumed. Any adult
human fibronectin-anti-fibronectin complexes formed do not bind
with the detection or control zones.
EXAMPLE 3
Operation of the Reflectance Reader
[0324] The test strip is read using the reflectance reader
exemplified herein. This reader (described above) is adapted to
read an immunochromatographic test strip supported within the
housing. The reflectance reader includes a cassette slot for
receiving the test-strip housing, and a sensing head assembly for
reading the test strip supported within the test-strip housing
using reflected light. The sensing head assembly includes a first
light-emitting diode (LED.sub.1), a second LED (LED.sub.2), a
silicon photodiode detector, and 39 optical fibers randomly
arranged in a narrow slit (e.g., 0.020'' wide) located at the
bottom of the sensing head assembly. LED.sub.1 emits light with a
wavelength of 430 nm (blue), and LED.sub.2 emits light with a
wavelength of 595 nm (amber). The optical fibers are arranged in
three groups of 13 optical fibers each: the first group transmits
light emitted by LED.sub.1 to the slit; the second group transmits
light emitted by LED.sub.2 to the slit; and the third group
transmits reflected light received at the slit to the
photodetector. The 39 fibers each include an end randomly arranged
within a plane located at the slit such that the ends are
co-planar, with the plane being normal to the test strip when the
sensing head assembly is positioned (as described below) to take
reflectance readings. The optical fibers in each of the three
groups are randomly arranged within the plane with respect to the
fibers of the other two groups.
[0325] The slit width is selected to be as narrow as permitted,
with the practical minimum being driven by the availability of
small diameter optical fibers. The maximum slit width should not be
larger than about 90% of the width of the colored stripe, otherwise
the background of the strip, in addition to the colored stripe,
will be read and less color will be detected, unless the slit, or
aperture, is positioned directly above the colored stripe.
[0326] When the housing is inserted into the cassette slot of the
reader, a spring mechanism rotates the sensing head directly over
the second aperture of the housing such that the plane defined by
the optical fibers is normal to the surface of the nitrocellulose
strip at a distance of about 0.010.'' Light from LED.sub.1 and
LED.sub.2 can be transmitted by the fibers onto the nitrocellulose
strip at a normal angle, and light reflected normally from the
strip can be transmitted by the fibers to the photodetector.
[0327] The sensing head takes three separate reflectance readings
of each portion of the nitrocellulose strip by reading the output
of the photosensor while controlling LED.sub.1 and LED.sub.2. The
first reading, used to determine the amount of ambient light
leaking into the reader (e.g., light leaking through the slot
entrance, or light reflected into the reader through the white
plastic of the housing), is a dark reading taken with LED.sub.1 and
LED.sub.2 both turned off. The dark reading count is subtracted
from the other two readings to correct for light leakage. The
second reading, used to determine background reflections associated
with the nitrocellulose, is taken with LED.sub.1 pulsed on and
LED.sub.2 turned off. The third reading, used to detect the
presence of the latex label on the test strip, is taken with
LED.sub.2 pulsed on and LED.sub.1 turned off. A control circuit
reads the photodetector output and controls the on and off
operation of LED.sub.1 and LED.sub.2. A memory circuit stores the
raw and/or processed data. The data also may be displayed to the
operator via an appropriate interface (e.g., an alphanumeric
character matrix).
[0328] After being positioned above the housing by the spring
mechanism, the sensing head can be moved slidably across the test
strip to allow the head to scan the entire exposed surface of the
nitrocellulose strip (including the detection and control zones).
In the preferred embodiment, this distance is approximately
0.452.'' The head is slidably connected to a rail (e.g., guide
rods), and is coupled to a worm or screw gear driven by a stepper
motor. Under the control of the control circuit, the stepper motor
drives the head along the rail in small steps (e.g., 0.002''/step).
At each step, the control circuit takes three readings as described
above. Thus, the control circuit moves the head such that the
optical fibers pass directly above and normal to the exposed
surface of the nitrocellulose strip in a sequence of small steps,
and takes a sequence of dark, LED.sub.1 and LED.sub.2 readings at
each step. The control circuit then processes the data read from
the photodetector at each sequence of three readings to determine
the presence or concentration of fFN.
[0329] Since the detection and control latex stripes are each about
0.020'' wide, and since each step of the sensing head is about
0.002'' long, there will be about 10 steps within each stripe.
Thus, there will be 10 sets of three readings (i.e., dark,
LED.sub.1 and LED.sub.2) at each of the stripes, and the remainder
of the reading sets will not be made over either stripe.
[0330] The control circuit processes the LED.sub.1 and LED.sub.2
readings by first subtracting the "dark reading" taken at the
corresponding step to correct for light leakage. The corrected
LED.sub.1 and LED.sub.2 readings are then input into a ratiometric
algorithm to determine the concentration of fFN. The algorithm is
based upon the ratio of readings at the detection and control
zones. If a sample includes a high concentration of fFN, latex
readings at the detection zone will be relatively high and the
readings at the control zone will be low. If the sample includes a
low concentration of fFN, however, latex readings at the detection
zone will be relatively low and readings at the control zone will
be high. The algorithm calculates a reflectance ratio for each step
which equals (amber count-dark count)/(blue count-dark count).
Generally, light leakage is so minimal that this step can be
omitted. If the reflectance ratio is graphed as a function of the
steps, the result will be a two-peak graph with the peaks occurring
at the two stripes. The graph is mathematically analyzed, with a
sigmoidal calculation across the background and a gaussian
calculation to integrate the area beneath each of the two peaks.
The fFN concentration is then determined based upon the ratio of
the integrated area beneath each of the two peaks.
[0331] In operation, when the test-strip housing is inserted into
the cassette slot of the reader, the sensing head rotates down over
the exposed nitrocellulose strip, and the control circuit then
moves the head to an initial position. The control circuit moves
the head across the exposed surface of the nitrocellulose strip,
including the detection and control zones, in small increments of
0.002'' each. At each step, the control circuit takes a first
reading of the photodetector output with LED.sub.1 and LED.sub.2
both off, takes a second reading with LED.sub.1 pulsed on and
LED.sub.2 off, and takes a third reading with LED.sub.1 off and
LED.sub.2 pulsed on. The control circuit then steps the sensing
head and repeats the three readings. This process is repeated for
each of 226 steps (0.452'' at 0.002''/step) until the entire
surface is read. The control circuit may then analyze the raw data
to determine the presence or concentration of fFN. The output
values can be displayed via an operator interface, or can be output
to another computer or apparatus.
[0332] Since modifications will be apparent to those of skill in
this art, it is intended that this invention be limited only by the
scope of the appended claims.
* * * * *