U.S. patent application number 10/770786 was filed with the patent office on 2004-08-12 for verification device for optical clinical assay systems.
This patent application is currently assigned to Beckman Coulter. Invention is credited to Downey, Thomas D., Meyer, Benjamin G., Zweig, Stephen E..
Application Number | 20040156045 10/770786 |
Document ID | / |
Family ID | 26737009 |
Filed Date | 2004-08-12 |
United States Patent
Application |
20040156045 |
Kind Code |
A1 |
Zweig, Stephen E. ; et
al. |
August 12, 2004 |
Verification device for optical clinical assay systems
Abstract
A device and method for verifying correct performance of an
optical clinical assay system is provided.
Inventors: |
Zweig, Stephen E.; (Los
Gatos, CA) ; Meyer, Benjamin G.; (Saratoga, CA)
; Downey, Thomas D.; (Cupertino, CA) |
Correspondence
Address: |
TOWNSEND AND TOWNSEND AND CREW, LLP
TWO EMBARCADERO CENTER
EIGHTH FLOOR
SAN FRANCISCO
CA
94111-3834
US
|
Assignee: |
Beckman Coulter
Fullerton
CA
|
Family ID: |
26737009 |
Appl. No.: |
10/770786 |
Filed: |
February 2, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10770786 |
Feb 2, 2004 |
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09564390 |
May 1, 2000 |
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09564390 |
May 1, 2000 |
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09138824 |
Aug 24, 1998 |
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6061128 |
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60057903 |
Sep 4, 1997 |
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Current U.S.
Class: |
356/243.4 |
Current CPC
Class: |
G01N 21/64 20130101;
G01N 21/8483 20130101; G01N 21/6428 20130101; G01N 2021/7786
20130101 |
Class at
Publication: |
356/243.4 |
International
Class: |
G01J 001/10 |
Claims
What is claimed is:
1. An electronically controlled optical reference device useful for
the verification of a clinical analytical system having an optical
detection apparatus, the reference device comprising: an opaque
optical reference; an optical shutter; means for controlling the
percent exposure of the optical reference to the optical detection
apparatus; optionally, a means to monitor the temperature of a
reaction stage of the clinical analytical system; and an algorithm
or method that controls the rate at which the optical reference is
selectively revealed to the optical detection apparatus, said
algorithm or method being selected as to simulate the reaction
rates of one or more levels of clinical analytes reacting with a
test reagent.
Description
[0001] This application is a continuation of, and claims the
benefit of priority from U.S. application Ser. No. 09/138,824,
filed Aug. 24, 1998 and (provisional) application No. 60/057,903,
filed on Sep. 4, 1997, the full disclosures of which are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] Increasingly in modern clinical chemistry, whole blood
samples, often obtained by finger stick methods, are analyzed using
automated automatic analysis systems (meters) which employ
disposable (often one-time use) test elements, and a non-disposable
electronic test device that analyzes the reaction occurring in the
whole blood sample in the disposable test element, and then outputs
an answer. Such systems are used for analyzing whole blood samples
for glucose, cholesterol, and increasingly, more complex tests such
as coagulation testing (prothrombin time, activated partial
thromboplastin time), enzymatic analytes, and the like.
[0003] Because the answer from these devices are often used to make
a clinical decision that can significantly impact the health and
well-being of a patient, verification methods to insure that the
analytical devices are performing correctly are of obvious
importance.
[0004] One common method for verifying correct performance of a
clinical analytical system is through the use of control solution,
which is usually a liquid chemical solution with known reactivity.
If the analytical device gives the correct answer with a known
reference chemical, then the overall performance of the system can
be assessed.
[0005] With modern one-shot, disposable test elements, however, the
problem with liquid control testing is that it is destructive. The
disposable test element has been destroyed as a result of the
testing, and only the now-validated meter now survives to test the
actual sample. For this reason, modern verification methods tend to
shift validation of disposable test elements to manufacturers, who
validate batches of disposable test elements by statistical
sampling methods. The problem of meter verification remains,
however. Meters are typically used for years, and can be exposed to
environmental extremes, misuse, and mechanical shock.
[0006] Because meter verification using liquid control devices and
disposable test units is an expensive process, and because test
unit verification is inherently best suited to statistical lot
testing by the manufacturer, there is a need for low-cost methods
that can verify the performance of the is meter without the use of
liquid control solution and disposable test units.
[0007] Analytical devices for temperature sensitive enzymatic
analytes, such as blood coagulation, typically have a temperature
controlled reaction stage, means to determine the start of the
enzymatic reaction, optical means to access the progress of the
reaction, and computational means (typically a microprocessor or
microcontroller) to interpret the progress of the reaction and
output an answer. To completely verify the performance of the
analysis system, each subsystem must be assessed. The temperature
controlled reaction stage must be tested for proper temperature
control, the means to determine the start of the enzymatic reaction
must be tested for proper sensitivity, the optical means to access
reaction progress must be tested (light source, light detector,
integrity of optical stage, etc.), and finally the computational
means must be tested. Alternatively partial verification of some of
the subsystems may be done, and the remainder of the subsystems
tested by alternate means, such as liquid control solution and a
disposable test unit.
[0008] To verify the function of such analytical devices,
electronic verification or "control" devices or circuits are
commonly used. Such verification devices can simulate the action of
an enzymatic sample interacting with a disposable reagent. If the
analytical device returns the proper answer after analysis of the
verification device, then the proper functioning of the analytical
device can be verified without the expense of using the one time
use reagent cartridges.
[0009] The use of reference paint chips to calibrate and verify
photometric devices has long been known in the art. When applied to
home blood glucose monitors, such reference chips are often
referred to as "check strips". For example, the LifeScan
One-Touch.TM. blood glucose monitor includes a calorimetric "check
strip" in with its meter system. This "check strip" consists of an
opaque plastic strip with a paint chip of known calorimetric
properties affixed to it. The check strip is inserted into the
meter, and is used to verify the performance of the meter's
colorimetric photodetector. The system does not vary the intensity
of the calorimetric paint chip target as a function of time to
simulate a normal test reaction, nor does it incorporate means to
monitor the analytical devices' temperature.
[0010] Recent refinements to the basic "paint chip" technique,
suitable for clinical reagents and instrumentation, include U.S.
Pat. Nos. 4,509,959; 4,523,852; 4,729,657; 5,151,755; 5,284,770;
and 5,592,290. U.S. Pat. No. 4,509,959 disclosed an apparatus
incorporating many such reference color chips. U.S. Pat. No.
4,523,852 disclosed a reference standard, suitable for visually
read diagnostic reagent test strips, consisting of many colored
reference areas of differing hues. U.S. Pat. No. 4,729,657
disclosed photometer calibration methods using two or more
reflectance standards and using least squares regression line
analysis to construct and store calibration curves in the
analytical device's memory. U.S. Pat. No. 5,151,755 disclosed
methods to detect defects in biochemical analysis apparatuses
measurement means by irradiating a reference density plate with
light that has passed through a plurality of interference filters
and comparing the relative amounts of reflected light obtained by
these different measurements. U.S. Pat. No. 5,284,770 disclosed use
of a check strip, along with an analytical instrument having a user
insertable key (memory chip) containing the parameters of
acceptable check strip performance, so that correct instrument
performance can be automatically verified. U.S. Pat. No. 5,592,290
disclosed optical analyzer instrument error correction methods
using standard color plates incorporating dyes with absorption
spectrum similar to the analytical reagent normally read by the
analyzer. These standard color plates are then used in conjunction
with a second reference optical analyzer and a specific correction
algorithm to correct the instrument error in the first
instrument.
[0011] In addition to passive "paint chip" verification methods, a
number of different active (typically electronic) verification
methods have also been used. These active verification methods
typically involve electronic components, and often produce a
dynamic (as opposed to a static) reference signal to the analytical
instrument.
[0012] U.S. Pat. No. 4,454,752 disclosed a test circuit for use in
a photometric coagulation instrument for plasma samples that
verified the electronic circuitry of the instrument, wherein the
rapid rise in clot density of a plasma sample may be simulated by a
applying to the clot detection circuitry of the instrument a
synthetic waveform that simulates the signal that results during
clot formation in a reagent plasma mixture. However, this patent
did not disclose methods by which the proper functioning of an
instrument capable of measuring whole blood can be analyzed. The
disclosed methods are capable of verifying only that the clot
detection circuits of an photometric plasma coagulation instrument
are performing properly. The patent did not disclose methods by
which other instrument functions such as temperature control,
absence of optical system light leaks, proper detection of sample
insertion, etc., may also be verified.
[0013] Verification methods suitable for partially verifying the
function of certain whole blood coagulation analyzers and unitized
reagent cartridges are also known in the art. For example, U.S.
Pat. Nos. 4,948,961 and 5,204,525 disclosed a quality control
device for an instrument with an analysis cartridge constructed so
that the instrument's light passes through the cartridge's internal
chamber. Such systems have been used for a number of whole blood
clinical tests, including whole blood prothrombin time assays when
the internal chamber is filled with thromboplastin, and the
cessation of red cell movement is tracked by light scattering
techniques.
[0014] U.S. Pat. No. 5,204,525 disclosed a control device using a
liquid crystal cell interposed between the light source and
detector in an analytical instrument, and a polarizing filter, so
that the passage or block passage of light between the analytical
device's light source and light detector when the voltage to the
liquid crystal is modulated. However, neither U.S. Pat. No.
5,204,525 nor U.S. Pat. No. 4,948,961 disclosed means by which the
temperature control of an analytical device may be verified.
Although these publications disclosed devices useful for monitoring
the function of optically transmissive reaction chambers in which
the light source passes through the chamber, and which the reaction
in question does not alter the wavelength of the light emitted by
the instrument's light source, they did not disclose devices useful
for monitoring the function of fluorescent test strip articles such
as those disclosed in U.S. Pat. No. 5,418,143. In such systems,
light of one wavelength enters a test strip, and excites a
fluorescent compound which then emits light that exits the test
strip at the same side as the light source (rather than passing
through a reaction chamber), and at a different wavelength.
[0015] Another type of control device is found in the Boehringer
Mannheim "Coaguchek" whole blood prothrombin time analysis device
disclosed by U.S. Pat. No. 4,849,340. This device uses a disposable
reagent cartridge consisting of a chamber with thromboplastin and
magnetic particles. The disposable reagent cartridge is placed in a
stage in the analysis device, and a blood sample is added. The
analysis device subjects the reagent cartridge to a varying
magnetic field, and detects the motion of the magnetic particles by
the optical interaction between the motion of the magnetic
particles and a beam of light. In normal operation, when blood is
applied to the disposable reagent cartridge, the magnetic particles
are free to move in suspension, and thus provide a high degree of
modulation to the optical signal in response to the varying
magnetic field. As the blood clots in response to the
thromboplastin reagent, the magnetic particles become less able to
move, and thus provide a progressively smaller amount of modulation
to the optical signal as time progresses.
[0016] An "electronic control" is provided for the Coaguchek.
(Boehringer Mannheim electronic control user manual, 1996) This
"electronic control" consists of a separate device consisting of a
disposable reagent sized probe that fits in to the reagent stage on
the Coaguchek device. The probe contains a magnetic coil pickup, a
light emitting diode, and means to vary the intensity of the
response of the light emitting diode to current generated by the
magnetic coil pickup. By using this "electronic control" device,
the operator can verify that the varying magnetic field generator
on the Coaguchek is operating properly, and that the optical sensor
on the Coaguchek is also operating properly. The temperature of the
reaction stage, and the performance of the optical light source on
the Coaguchek, are not tested by this device, however.
[0017] In addition to passive (time unvarying reference signal) and
active (time varying reference signal) verification devices, a
third type of verification methodology has been disclosed which
incorporates certain verification systems on to the disposable
reagent itself. This is disclosed by in U.S. Pat. Nos. 5,591,403
and 5,504,011. U.S. Pat. No. 5,591,403 disclosed a reaction chamber
cuvette, useful for prothrombin time testing, with multiple
conduits. One or more conduits contain the reaction chemistry for
the prothrombin time reaction itself, and other conduits contain
control agents useful for assessing certain functions of the
analytical instrument that reads the test cartridge, and the test
cartridge itself. Typically one "control" conduit will contain a
vitamin K dependent clotting factor concentrate, and a different
"control" conduit will contain an anticoagulant. In a properly
functioning instrument, the control conduit with the vitamin K
dependent clotting factor concentrate will initiate a coagulation
signal early, and the control conduit with the anticoagulant will
initiate a coagulation signal late. This tests the proper function
of those meter detector elements that read the status of the
control conduits. Because the control elements are incorporated
into normal prothrombin time reaction cuvette, an independent,
non-destructive, test of proper meter function is not possible with
this system.
[0018] Thus, a need exists for an improved verification device.
This need and others are addressed by the instant invention.
SUMMARY OF THE INVENTION
[0019] One aspect of the invention is a method for verifying the
output of a system having a radiation source and a radiation
detector, said method comprising positioning a reference surface to
receive radiation from the radiation source and return radiation to
the detector; and modulating at least one of the radiation from the
source and the radiation to the detector over time to emulate
reflective or radiation characteristics of a chemical or biological
reaction on the reference surface.
[0020] A further aspect of the invention is a method for verifying
the output of a system having a radiation source and a radiation
detector, said method comprising positioning a reference surface to
receive radiation from the radiation source and return radiation to
the detector; and modulating at least one of the radiation from the
source and the radiation to the detector over time in response to
temperature changes. In some embodiments, the temperature changes
are determined within the system. In further embodiments, the
temperature changes are determined external to the system.
[0021] A further aspect of the invention is an apparatus for use in
combination with an analyzer having a radiation source and a
radiation detector, said apparatus comprising a reference surface
which produces return radiation in response to receiving radiation
from the source, and means disposed adjacent the radiation surface
for modulating at least one of radiation to the reference surface
or radiation from the reference surface. In some embodiments the
modulating means modulates the radiation over time to emulate
reflective or radiation characteristics of a chemical or biological
reaction on the reference surface. In further embodiments the
modulation means modulates the radiation in response to changes in
temperature.
[0022] A further aspect of the invention is an electronically
controlled optical reference device useful for the verification of
a clinical analytical system having an optical detection apparatus,
the reference device comprising, an opaque optical reference; an
optical shutter; means for controlling the percent exposure of the
optical reference to the optical detection apparatus; optionally, a
means to monitor the temperature of a reaction stage of the
clinical analytical system; and an algorithm or method that
controls the rate at which the optical reference is selectively
revealed to the optical detection apparatus, said algorithm or
method being selected as to simulate the reaction rates of one or
more levels of clinical analytes reacting with a test reagent.
[0023] A further aspect of the invention is a verification device
useful for determining the proper function of an optical,
temperature controlled analytical instrument, the device comprising
an electronic optical shutter with an optically active backing,
interposed between an optical signal emitted by the analytical
instrument and an optical detector mounted on the analytical
instrument; a temperature sensor, the sensor contacting a reaction
stage on the analytical instrument; and verification device
electrodes, the verification device electrodes making contact with
electrodes on the reaction stage of the analytical instrument;
wherein the action of the device is initiated by a resistance drop
across the verification device electrodes, and wherein the optical
transmission of the liquid crystal shutter is modulated as a
function of time and of the temperature of the reaction stage,
wherein a range of levels of enzymatic activity measured by the
analytical instrument at various operating temperatures is
simulated.
[0024] A further aspect of the invention is a verification device
useful for determining the proper function of an optical,
temperature controlled analytical instrument, the device comprising
an optical shutter-fluorescent backing assembly comprising an
optical shutter having a fluorescent backing placed on one side of
the optical shutter; the assembly being interposed between an
optical signal emitted by the analytical instrument and an optical
detector mounted on the analytical instrument; a thermocouple in
contact with a reaction stage on the analytical instrument; and
verification device electrodes, the verification device electrodes
making contact with electrodes on the reaction stage of the
analytical instrument; wherein the action of the device is
initiated by a resistance drop across the device electrode, and
wherein the fluorescence of the optical shutter-fluorescent backing
assembly is modulated as a function of time and of the temperature
of the reaction stage, wherein a range of levels of enzymatic
activity measured by the analytical instrument at various operating
temperatures is simulated.
[0025] A further aspect of the invention is an electronically
controlled optical reference device, useful for the verification of
an analytical instrument having an optical detection apparatus and
using optically read reagent test strips, the device comprising an
opaque optical reference, which simulates the optical
characteristics of a reagent test strip after reaction with its
intended clinical sample; an optical shutter; a means for
controlling the percent exposure of the optical reference to the
optical detection apparatus; and an algorithm or method that
controls the rate at which the check strip is selectively revealed
to the optical detection apparatus, said algorithm or method being
selected as to mimic the reaction rates of one or more levels of
clinical analytes reacting with a reagent test strip.
[0026] A further aspect of the invention is a method for verifying
the correct performance of a clinical analytical system comprising
an optical detection apparatus, the method comprising contacting
the clinical analytical system with an electronically controlled
optical reference device useful for the verification of clinical
devices using optically read reagent test strips, the reference
device comprising, an opaque optical reference, which simulates the
optical characteristics of a reagent test strip after reaction with
its intended clinical sample; an optical shutter; means for
controlling the percent exposure of the optical reference to the
optical detection apparatus; optionally, a means to monitor the
temperature of the clinical analytical system; and an algorithm or
method that controls the rate at which the optical reference is
selectively revealed to the optical device, said algorithm or
method being selected so as to mimic the reaction rates of one or
more levels of clinical analytes reacting with a reagent test
strip; and analyzing the optical reference; wherein an expected
result of analysis of the optical reference by the clinical
analytical system is predictive of the correct performance of the
clinical analytical system.
[0027] A further aspect of the invention is a method for verifying
the temperature control of a clinical analytical system comprising
an optical detection apparatus, the method comprising contacting
the clinical analytical system with a verification device useful
for determining the proper function of an optical, temperature
controlled analytical instrument, the device comprising an
electronic optical shutter with an optically active backing,
interposed between an optical signal emitted by the analytical
instrument and an optical detector mounted on the enzymatic
analytical instrument; a temperature sensor, the sensor contacting
a reaction chamber on the analytical instrument; and verification
device electrodes, the verification device electrodes making
contact with electrodes on the reaction chamber of the analytical
instrument; wherein the action of the device is initiated by a
resistance drop across the verification device electrodes, and
wherein the optical transmission of the liquid crystal shutter is
modulated as a function of time and of the temperature of the
reaction chamber, wherein a range of levels of enzymatic activity
measured by the analytical instrument at a range of operating
temperatures is simulated, and analyzing the optical reference;
wherein an expected result of analysis of the optical reference by
the clinical analytical system is predictive of the correct
operating temperature of the reaction chamber of the clinical
analytical system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 is a diagram depicting an electronic strip emulator
constructed according to the principles of this disclosure (outside
the dotted box), interacting with an exemplary test device (inside
the dotted box).
[0029] FIGS. 2A and 2B depict two types of optical shutters. The
shutter in FIG. 2A comprises a single shutter element, which can be
gradually varied from non-transmissive to transmissive. The optical
shutter in FIG. 2B comprises numerous shutter "pixel" elements.
[0030] FIG. 3 is a graph depicting the output from the electronic
verification device when the analytical device (meter) is at a
normal temperature (37.degree. C.), and at an aberrant temperature
(33.degree. C.). Here, Level I mimics a prothrombin time reaction
curve obtained from a test sample with a normal prothrombin time
value, and Level II mimics the prothrombin time reaction curve
obtained from a test sample with an elevated prothrombin time
value.
[0031] FIG. 4 depicts an example of a temperature correction
algorithm altering the kinetics of fluorescence development in
response to the time averaged temperature readings from the
electronic verification device. The temperature algorithm is
selected to match the temperature response of a real reagent test
strip.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0032] The present invention provides a method for verifying the
output of a system having a radiation source and a radiation
detector, said method comprising positioning a reference surface to
receive radiation from the radiation source and return radiation to
the detector; and modulating at least one of the radiation from the
source and the radiation to the detector over time to emulate
reflective or radiation characteristics of a chemical or biological
reaction on the reference surface. In some aspects of the
invention, the modulator may operate without the reference surface
by selectively reflecting light.
[0033] The present invention also provides a method for verifying
the output of a system having a radiation source and a radiation
detector, said method comprising positioning a reference surface to
receive radiation from the radiation source and return radiation to
the detector; and modulating at least one of the radiation from the
source and the radiation to the detector over time in response to
temperature changes. In some embodiments, the temperature changes
are determined within the system. In further embodiments, the
temperature changes are determined external to the system.
[0034] The present invention also provides an apparatus for use in
combination with an analyzer having a radiation source and a
radiation detector, said apparatus comprising a reference surface
which produces return radiation in response to receiving radiation
from the source, and means disposed adjacent the radiation surface
for modulating at least one of radiation to the reference surface
or radiation from the reference surface. In some embodiments the
modulating means modulates the radiation over time to emulate
reflective or radiation characteristics of a chemical or biological
reaction on the reference surface. In further embodiments the
modulation means modulates the radiation in response to changes in
temperature.
[0035] The present invention also provides a verification device
for a clinical analytical system or instrument. Such a device is
also referred to herein as a test strip emulator, a control test
simulator, and an electronically controlled optical reference
device. The verification device is typically an electronically
controlled optical reference device useful for the verification of
a clinical analytical system having an optical detection apparatus.
The reference device comprised an opaque optical reference or
"target", an optical shutter, and means for controlling the percent
exposure of the optical reference to the optical detection
apparatus. The opaque optical reference preferably simulates a
calorimetric, fluorescent, or luminescent reagent test strip.
Optionally, a means to monitor the temperature of a reaction stage
of the clinical analytical system is included as part of the
device. The device is preferably programed with an algorithm or
comprises a method that controls the rate at which the optical
reference is selectively revealed to the optical detection
apparatus. Typically the selective revealing of the optical
reference is done by exposing the optical reference to the optical
detection apparatus over a specified time interval. The algorithm
or method is selected so as to simulate the reaction rates of one
or more levels of clinical analytes reacting with a test reagent.
The algorithm or method can be modified to account for the
temperature of a reaction stage or chamber in the analytical
system.
[0036] In some embodiments of the invention, the device of
comprises one or more first electrodes, wherein electrodes contact
one or more second electrodes on a reaction stage of the clinical
analytical system. The electrical resistance across the electrodes
in the reference device is modulated to simulate the addition or
removal of a disposable reagent test strip or cartridge or a liquid
sample to the clinical analytical system.
[0037] The optical shutter of the device may be electronically
operated. Exemplary shutters include but are not limited to a
liquid crystal shutter, a magneto-optical shutter, a Faraday effect
optical shutter, a thermochromic optical shutter, an electrochromic
optical shutter, or a micro-mechanical optical shutter. The optical
shutter may be divided into a plurality of independently or
semi-independently controlled pixel elements, such that the optical
shutter modulates the intensity of an optical signal by varying the
optical state of the shutter pixels in a time dependent manner.
[0038] In some embodiments, the optical shutter comprises a
fluorescent backing on one side of the optical shutter, and a first
optical signal of a first wavelength passes through the optical
shutter and interacts with the fluorescence backing, and a
fluorescence signal of a second wavelength passes back through the
optical shutter. In further embodiments, the optical shutter
comprises a colored backing on one side of the optical shutter, and
a first optical signal consisting of a first spectrum of
wavelengths passes through the optical shutter and interacts with
the colored backing, and a second optical signal consisting of a
subset of the first spectrum of wavelengths passes back through the
optical shutter. The optical shutter may also comprise a
luminescent backing on one side of the optical shutter, with the
optical signal comprising a time increasing or time decreasing
luminescence signal.
[0039] In a further feature of the invention, a thermocouple
monitors the temperature of the reaction stage of the analytical
device. The transparency of the optical shutter may be modulated as
a function of time and of a thermocouple monitored temperature of
the reaction stage, wherein a range of levels of enzymatic activity
measured by the analytical system at various operating temperatures
is simulated.
[0040] In some embodiments of the invention, the verification
device provides a means to monitor a reagent present and/or blood
present sensor on the clinical analytical device, wherein a
stimulus to these sensors is provided to signal readiness of the
meter for testing a clinical sample.
[0041] The instant invention also provides a verification device
useful for determining the proper function of an optical,
temperature controlled analytical instrument. Typically such a
device will comprise an electronic optical shutter with an
optically active backing, interposed between an optical signal
emitted by the analytical instrument and an optical detector
mounted on the analytical instrument; a temperature sensor, the
sensor contacting a reaction stage on the analytical instrument;
and verification device electrodes, the verification device
electrodes making contact with electrodes on the reaction stage of
the analytical instrument. The action of the device is preferably
initiated by a resistance drop across the verification device
electrodes. The optical transmission of the liquid crystal shutter
is modulated as a function of time and of the temperature of the
reaction stage, wherein a range of levels of enzymatic activity
measured by the analytical instrument at various operating
temperatures is simulated. The reaction stage of the analytical
device may be heated.
[0042] In some embodiments the device comprises an optical
shutter-fluorescent backing assembly comprising an optical shutter
having a fluorescent backing placed on one side of the optical
shutter; the assembly being interposed between an optical signal
emitted by the analytical instrument and an optical detector
mounted on the analytical instrument; a thermocouple in contact
with a reaction stage on the is analytical instrument; and
verification device electrodes, the verification device electrodes
making contact with electrodes on the reaction stage of the
analytical instrument. The action of the device is initiated by a
resistance drop across the device electrode. The fluorescence of
the optical shutter-fluorescent backing assembly is modulated as a
function of time and of the temperature of the reaction stage,
wherein a range of levels of enzymatic activity measured by the
analytical instrument at various operating temperatures is
simulated. The reaction stage of the analytical device may be
heated.
[0043] The instant invention also provides an electronically
controlled optical reference device, useful for the verification of
an analytical instrument having an optical detection apparatus and
using optically read reagent test strips. The device comprises an
opaque optical reference, which simulates the optical
characteristics of a reagent test strip after reaction with its
intended clinical sample; an optical shutter; a means for
controlling the percent exposure of the optical reference to the
optical detection apparatus; and an algorithm or method that
controls the rate at which the check strip is selectively revealed
to the optical detection apparatus, said algorithm or method being
selected as to mimic the reaction rates of one or more levels of
clinical analytes reacting with a reagent test strip. In a
preferred embodiment, the reagent is thromboplastin.
[0044] The instant invention also provides a method for verifying
the correct performance of a clinical analytical system comprising
an optical detection apparatus using teh devices of the instant
invention. In a preferred embodiment, the clinical analytical
system is contacted with an electronically controlled optical
reference device useful for the verification of clinical devices
using optically read reagent test strips. The reference device, for
example, comprises an opaque optical reference, which simulates the
optical characteristics of a reagent test strip after reaction with
its intended clinical sample; an optical shutter; means for
controlling the percent exposure of the optical reference is to the
optical detection apparatus; optionally, a means to monitor the
temperature of the clinical analytical system; and an algorithm or
method that controls the rate at which the optical reference is
selectively revealed to the optical device, said algorithm or
method being selected as to mimic the reaction rates of one or more
levels of clinical analytes reacting with a reagent test strip. An
expected result of analysis of the optical reference by the
clinical analytical system is predictive of the correct performance
of the clinical analytical system.
[0045] The instant invention also provides a method for verifying
the temperature control of a clinical analytical system comprising
an optical detection apparatus using the devices of the instant
invention. In a preferred embodiment, the method comprises
contacting the clinical analytical system with a verification
device useful for determining the proper function of an optical,
temperature controlled analytical instrument. For example, the
device comprises an electronic optical shutter with an optically
active backing, interposed between an optical signal emitted by the
analytical instrument and an optical detector mounted on the
enzymatic analytical instrument; a temperature sensor, the sensor
contacting a reaction chamber on the analytical instrument; and
verification device electrodes, the verification device electrodes
making contact with electrodes on the reaction chamber of the
analytical instrument. The action of the device is initiated by a
resistance drop across the verification device electrodes, and
wherein the optical transmission of the liquid crystal shutter is
modulated as a function of time and of the temperature of the
reaction chamber, wherein a range of levels of enzymatic activity
measured by the analytical instrument at a range of operating
temperatures is simulated. An expected result of analysis of the
optical reference by the clinical analytical system is predictive
of the correct operating temperature of the reaction chamber of the
clinical analytical system.
[0046] The verification device of the invention can be provided as
a probe, suitable for insertion into the reaction chamber of a
calorimetric, fluorescent, or chemiluminescent test analytical
instrument, with an opaque colorimetric, fluorescent or luminescent
target. The reflectance, fluorescence or luminescence of the target
is modulated by an optical shutter. Typically the probe will
additionally contain a temperature sensor, a clock, and means to
modulate the optical exposure of the probes target area according
to a preset algorithm. The preset algorithm is designed to mimic
the response of a normal reagent with one or more levels of test
analyte. The probe may optionally contain other elements designed
to interact with and test other meter functional elements, such as
a meters "reagent present" and "sample present" sensors.
[0047] The optical characteristics of the opaque optical target can
vary depending upon the analytical device in question. In one
embodiment, the target is optically reflective and/or optically
colored, so as to effectively change the distribution of various
wavelengths or light intensity of the target as a function of the
state of the optical shutter. In a further embodiment, the target
can made of a fluorescent material, so that the fluorescent
intensity of the light detected by the analytical system's detector
varies as a function of the state of the optical shutter. In a
third embodiment, the backing can be luminescent (for example, an
electronic luminescent panel), so that the luminescence seen by the
analytical system's luminescence detector varies as a function of
the state of the optical shutter. Although for brevity, this
discussion will focus on fluorescent targets, it should be
understood that the same principles would also apply to
calorimetric or luminescent analytical systems as well.
[0048] A fluorescent target is typically composed of a fluorescent
compound, with absorption and emission characteristics similar to
that of the analytical devices normal fluorescent reagent. The
compound will typically be incorporated into a rigid support
matrix. This can be done by mixing the fluorescent target compound
with a suitable support carrier, such as acrylic paint, epoxy, or
the like. To maximize the optical signal-to-noise characteristics
of the fluorescent target, sufficient quantities of fluorescent
compound are added as to completely interact with the entire
fluorescence optical excitation signal, rendering the target
optically opaque. The fluorescent target shifts the wavelength of
the excitation signal to a different wavelength, and the
fluorescent signal emerges from the side of the target that is
illuminated by the excitation wavelength.
[0049] Alternatively, if it is infeasible to make the target opaque
using large amounts of fluorescent compound, the back of the target
may painted with an opaque backing. The characteristics of this
opaque backing may be selected to maximize the signal-to-noise
performance of the fluorescent target. If the optical cutoff
efficiency of the fluorescent detector's filters to the
fluorescence excitation wavelengths is high, the opaque backing
could be selected to be of a shiny reflective material.
Alternatively, if the optical cutoff efficiency of the fluorescent
detector's filters to the fluorescence excitation wavelengths is
lower, a non-reflective (black) opaque backing may be chosen to
minimize back reflections of the incoming excitation wavelengths to
the fluorescence detector.
[0050] In yet another embodiment, the target may be luminescent,
and used in a chemiluminescence detecting analytical device that
has an optical detector, but does not contain a light source. The
light source for the luminescent target may be provided by variety
of conventional electrical lighting techniques.
[0051] The optical shutter may be a mechanical or
electro-mechanical shutter, such as an iris as typically used to
control exposure intensity in cameras, a series of louvers, or the
like. Alternatively, the optical shutter may be an electro-optical
shutter, such as a liquid crystal shutter, a magneto-optical
electric shutter, Faraday effect optical shutter, thermochromic
optical shutter, Electrochromic optical shutter, micro-mechanical
optical shutter, or other such device. Some exemplary optical
stutters suitable for the present invention are disclosed, for
example, in U.S. Pat. Nos. 3,649,105; 4,556,289; 4,805,996;
4,818,080; 5,050,968; 5,455,083; 5,459,602; and 5,525,430.
[0052] The optical shutter may be composed of a single functional
shutter element, or alternatively it may be composed of many
smaller functional shutter elements, that collectively act to act
to alter the optical characteristics of the shutter as a whole.
[0053] In an configuration, the shutter is mounted so that light
illuminating the optical (fluorescent) target passes through the
shutter. Fluorescent light re-emitted by the optical target may
pass directly to the analytical device fluorescence detector, or
optionally pass through the optical shutter on the way to the
fluorescence detector. Alternatively, the optical shutter can be
mounted to interact only with light emitted by the optical target.
In still a further configuration, the optical shutter can interact
with light both illuminating and emitted by the optical target.
[0054] The device may optionally contain means of monitoring the
temperature of the probe near the target area, as well as means of
modulating the fluorescence signal in response to the temperature
of the target area. These means may be mechanical, such as a
bimetallic strip mechanical temperature sensor device hooked up to
a mechanical shutter, chemical, such as a temperature sensitive
liquid crystal thermometer, or electronic, such as a thermistor,
thermocouple, or the like. In the preferred embodiment, the
temperature sensor is electronic.
[0055] The means to modulate the target's fluorescence may be
mechanical, such as a clockwork mechanism, cam, or the like. The
means may be controlled by analog electrical circuits, such as
simple analog timers or the like, or the means may be controlled by
digital electrical circuits, such as microprocessors,
microcontrollers, and the like. In the case of mechanical means,
the algorithm encoding the state of the target's fluorescence as a
function of time is encoded into the design of the mechanical
timing elements. In the case of analog electrical circuits, the
algorithm is encoded by properly selected time constants, and the
like. In the preferred case of digital microprocessor controllers,
the algorithm is encoded by a specific program that controls
fluorescence as a function of time, and optionally temperature and
other variables.
[0056] To fully validate the analytical system's performance over a
variety of sample ranges, the algorithm will ideally simulate the
reaction occurring when samples with different relative activity
react with test reagents. The algorithm may switch from simulating
one test level to a different test level either in response to user
input, or automatically as the test algorithm runs through a preset
series of validation tests.
[0057] The verification device's probe may optionally contain one
or more additional elements that interact with and validate other
aspects of the proper function of the analytical system. For
example, the probe may test the function of systems that determine
if a cartridge has been properly inserted, or systems that
determine if sufficient sample has been added. In the case of
optical strip insertion or sample addition schemes, the probe may
contain additional light emitting or light blocking devices
designed to interact with appropriate optical detectors on the
instrument. Alternatively, in the case of electronic strip
insertion or sample addition schemes, such as those disclosed in
U.S. Pat. Nos. 5,344,754 and 5,554,531, and in Zweig et. al.,
Biomedical Instrumentation & Technology 30: 245-256 (1996), the
probe may contain one or more electrodes that interact with
corresponding electrode sensors on the analytical device, and
provide appropriate inputs to simulate normal activity.
[0058] The verification device may be constructed as a stand-alone,
independently powered unit. This may be manually inserted or
removed by the user, or inserted or removed by automated equipment.
Alternatively, the verification device may be constructed as an
integral part of the analytical device itself, and may share one or
more elements (power supply, microprocessor time, memory, etc.)
with the analytical device.
[0059] A schematic diagram of the verification device of the
instant invention interacting with a meter is depicted in FIG. 1.
In this embodiment, the meter 40 consists of an electrically heated
support stage 27, containing an optical window 30 through which
light 22 emitted from light source 21 can pass. The meter
additionally contains an optional fluorescence filter 24 and a
photodetector 26. In normal use, light 22 travels through the
optics window 30 and illuminates a fluorescent reagent target.
Fluorescent light 23 travels though filter 24 and after filtration
illuminates photodetector 26. The meter is controlled by a
microprocessor 29, which initiates test timing in response to
inputs from strip detect and sample detection electrodes 28. The
verification device circuit board additionally contains electrodes
14 that interacts with the strip detect and blood detect electrodes
28 on the meter's optics block 20. A thermocouple 11 performs an
independent measurement of the temperature of the meter's heated
optics block 27. The verification device has an optical shutter 12,
with a backing 13, and a circuit board 10. A microcontroller 15 is
also provided.
[0060] In a preferred embodiment, the verification device has an
8.times.8 pixel liquid crystal optical shutter 12, with an active
area of 0.375.times.0.375", and an exterior size of
0.5".times.0.6", made by Polytronics, Inc. This is placed on a
0.02" thick circuit board 10, with exterior dimensions of 0.75",
and length of 2". The exterior circuit board is made to the same
size as a disposable test strip unit normally used in an Avocet
Medical prothrombin time detector (see Zweig, et al., Biomedical
Instrumentation & Technology 30, 245-256; FIGS. 3 and 4).
[0061] The optical shutter has a backing 13 consisting of Rhodamine
110 mixed with epoxy. The rhodamine 110 retains its normal
fluorescence activity when mixed with the epoxy, and the epoxy
provided a way to affix the Rhodamine 110 to the back of the
optical shutter 12 in durable and permanent manner. The active
elements on the circuit board are controlled by a Texas Instruments
TSS400-S3 sensor signal processor 15, which is a combination
microcontroller, liquid is crystal display driver, and A/D
converter. The TSS400 additionally contains 2 K bytes of
programmable EEPROM, which contained the algorithm needed to drive
the system.
[0062] When turned on (switches not shown), the verification device
initially turns all 64 pixels of the 8.times.8 pixel optical
shutter to the opaque mode. Electrodes 14 connecting to the strip
present sensors 28 on the meter's optics block 20 are switched to
conducting mode (resistance is lowered), to allow the Avocet Meter
to detect that a test strip is inserted into the optics block. The
meter then initiates a warm-up sequence.
[0063] In this preferred embodiment, upon reaching proper
temperature, the meter then sends a signal via its sensor
electrodes 28 to the verification device electrodes 14 informing
the verification device that the meter is now warmed up.
Alternatively, the meter can signal to the user that it is ready,
and the user can manually transfer this information to the
verification device by pressing an electrical switch on the
verification device. After the verification device is informed that
the meter is now ready to proceed, the device then reduces the
resistance across a second set of electrodes 44, which interact
with the blood present sensors 42 on the meter's optics block.
Whereas this resistance drop is normally used to signal the
application of blood to the reagent strip (see, for example, U.S.
Pat. No. 5,344,754), in the instant invention it is used to signal
the meter to proceed even though no blood has actually been
applied.
[0064] In this preferred embodiment, the microcontroller 15 on the
verification device consults an algorithm, and selectively switches
an increasingly larger number of pixels on the liquid crystal
shutter 12 to transparent mode as a function of a number of
variables, including time, the setting of the verification device
(e.g. Level I or II control, etc.), and optionally the temperature
of the meter's optics stage 27 as measured by temperature sensor
11. The meter optical system 20 observes the fluorescent backing 13
through the optical shutter 12, and observes a progressive increase
in overall fluorescence as a function of time. Alternatively, the
verification device can progressively alter the voltage applied to
a single element optical shutter element (see FIG. 2A) so as to
progressively increase the transparency of the single element
shutter as a function of time and temperature.
[0065] Exemplary algorithms are as follows. The verification device
contains one or more stored reaction profile algorithms that
control the percent light transmission of the optical shutter as a
function of time. A preferred Level I algorithm is:
% fluorescence(% pixels switched on)=100*[0.01*Reaction
time-0.0.35] Equation 1:
% fluorescence(% pixels switched on)=100*[0.02*Reaction time-0.9]
Equation 2:
% fluorescence(% pixels switched on)=100*[0.01*Reaction time-0.05]
Equation 3:
[0066] In a preferred embodiment, every ten seconds (the frequency
at which the meter took data) for 240 seconds (a typical test
duration) the verification device computes all three equations, and
chose the results based upon the rule:
[0067] If Equation 1<0, % fluorescence=0;
[0068] If Equation 1>0 and <20%, % fluorescence=Equation
1
[0069] If Equation 1>20% and Equation 2<80%, %
fluorescence=Equation 2
[0070] If Equation 2>80% and Equation 3<100%, %
fluorescence=Equation 3
[0071] If Equation 3>100%, % fluorescence=100%.
[0072] This produces an "S" shaped reaction profile, shown in FIG.
3, similar to that of a normal prothrombin time (Level I) sample.
In contrast, an exemplary algorithm used for the elevated
prothrombin time (Level II) control is:
% fluorescence(% pixels on)=100*[0.007*Reaction time-0.6] Equation
1, 2, and 3:
[0073] The decision tree is the same as the Level I control shown
previously. This produces a delayed, lower slope, linear curve more
typical of that of a normal Level II sample reaction.
[0074] A typical temperature verification algorithm is as follows.
To verify that the meter's optical stage is being maintained at the
proper temperature, the thermocouple on the electronic verification
device periodically (every second) performs a temperature
measurement. The results from each temperature are converted into
degrees C. if necessary. The degree of deviation of the measured
temperature from the ideal temperature is used as input into a
temperature correction algorithm. This temperature correction
algorithm advances or retards the schedule of pixel switching on
the optical shutter in such a way as to mimic the response of a
normal test strip-reagent reaction reacting at a deviant
temperature. For a prothrombin time reaction, previous work (Daka
et al., Journal of Investigative Surgery 4: 279-290; 1991), has
shown that the optimal reaction temperature for a prothrombin time
test is at a reaction time minima, and deviations from this ideal
temperature, either positive or negative, prolong the prothrombin
time value.
[0075] In a normal reagent reaction, the effects of temperature are
cumulative. That is, a reaction held at the proper temperature for
95% of the reaction will be only mildly affected if the temperature
is slightly deviant during 5% of the reaction. For an exemplary
prothrombin time reaction, the effects of non-ideal temperature
(either positive or negative) is to slow down the reaction (the
ideal temperature is at a reaction time minima). Our own work, as
well as the work of Daka et. al., has shown that for the
prothrombin time verification device discussed by example here, the
effects of non-ideal temperatures on the prothrombin time reaction
can be approximated by the equation:
Fluorescence(Time,Temp)=Fluorescence(Time-(a*(Temperature
Deviation)2),
[0076] where "a" is an experimentally determined coefficient (here
taken to be 0.1) used to bring the validation device's temperature
variation in line with those of an actual reagent test strip.
[0077] The verification device reaction profile, described by the
Level I and II equations above, can be temperature compensated to
match a normal reagent reaction profile, reacting at a deviant
temperature, by subtracting a factor proportional to the time
weighted temperature deviation average from the % fluorescence
calculation at each relevant time point. This delays the onset of
fluorescent development. Higher order polynomial fits, or other
temperature compensation functions, can also be used for these
purposes.
[0078] The meter's microcontroller takes a series of fluorescence
readings as for a normal test strip, and interprets the result
according to its normal test strip algorithm. Previous work (U.S.
Pat. No. 4,418,141 and the Zweig et. al., supra), has shown that
for the prothrombin time example illustrated here, the prothrombin
time (PT) time correlates linearly with the time at which the
normalized fluorescence reaction profile first exceeds 10% of its
maximum value (Time 10%). Thus by shifting the time at which the
verification device reaction profile first exceeds 10% of its
maximum value; the temperature compensation algorithm will cause a
corresponding shift in the prothrombin time value reported by the
meter after reading the verification device.
[0079] FIG. 3 depicts the verification devices' fluorescence
profiles reacting according to the Level I and Level II algorithm
at a simulated optimal temperature of 37.degree. C., and at an
aberrant lower temperature. FIG. 4 shows graphically how the
verification device's temperature correction algorithm delays the
initial onset of the fluorescent signal (Time 10%) for meters
operating at aberrant temperatures.
[0080] If the meter is working properly, the answer displayed will
be within the expected parameters. If the fluorescence detector is
working improperly, the meter's internal error detection mechanisms
will detect a problem (no signal or erratic signal) and display an
error code. If the meter's stage is at the incorrect temperature,
the deviant pattern of pixel switching on the electronic strip
emulator causes the meter to output an answer outside of the
expected parameters. The user can either be instructed to not use
the system when this happens, and or the meter can itself examine
the results, and automatically lock itself into a "safe" mode to
prevent outputting an erroneous answer when a real sample is
used.
EXPERIMENTAL EXAMPLES
[0081] The device constructed according to the preferred embodiment
disclosed above was constructed. A fluorescent backing was provided
by first mixing 50 mg/ml of Rhodamine-123 in 10 ml of isopropyl
alcohol solution, to produce a 5 mg/ml Rhodamine-123 solution. This
was mixed in a 1:3 ratio with "Clear Gloss" acrylic finish (lot
404100, Floquil-Pollt S Color Corp., Amsterdam N.Y.) The Rhodamine
dye mixed evenly with this acrylic paint. 10 microliters of this
acrylic paint-dye mix was then applied to the back of a Polytronics
liquid crystal shutter, and allowed to air dry. When dry, the paint
formed a clear durable finish encapsulating the Rhodamine-dye.
After drying, the back of the liquid crystal shutter was further
coated with black epoxy, forming a more durable, and light opaque
fluorescence backing.
[0082] The verification device was then programmed as described
above for the preferred embodiment, and tested in a prototype
Avocet PT-1000 prothrombin time instrument. The instrument
responded to the verification device as it would to a normal test
strip reacting with sample, and produced appropriate Level I
(normal prothrombin time) and appropriate Level II (prolonged
prothrombin time) answers.
[0083] All references (including appendices, books, articles,
papers, patents, and patent applications) cited herein are hereby
expressly incorporated by reference in their entirety for all
purposes.
[0084] While the invention has been described in connection with
specific embodiments thereof, it will be understood that it is
capable of further modification, and this application is intended
to cover any variations, uses, or adaptations of the invention
following, in general, the principles of the invention and
including such departures from the present disclosure as come
within known or customary practice in the art to which the
invention pertains and as may be applied to the essential features
hereinbefore set forth, and as fall within the scope of the
invention and the limits of the appended claims.
* * * * *