U.S. patent application number 10/189729 was filed with the patent office on 2002-11-28 for system, method and computer implemented process for assaying coagulation in fluid samples.
This patent application is currently assigned to i-STAT Corporation. Invention is credited to Lauks, Imants R., Maczuszenko, Andy, Opalsky, David, Widrig Opalsky, Cindra A..
Application Number | 20020177958 10/189729 |
Document ID | / |
Family ID | 22664737 |
Filed Date | 2002-11-28 |
United States Patent
Application |
20020177958 |
Kind Code |
A1 |
Widrig Opalsky, Cindra A. ;
et al. |
November 28, 2002 |
System, method and computer implemented process for assaying
coagulation in fluid samples
Abstract
A sample analyzing system includes at least one sensor located
at least partially within a sample retaining area. In addition, the
sensor has at least one edge defining a sample detection location.
This sample detection location defines an area within which the
sensor is capable of detecting a presence or an absence of the
sample. The system analyzes sample data by first introducing the
sample into the sample retaining area and then mixing a reagent
with the sample to commence formation of a reagent product. After
mixing and upon detecting the absence of the sample from the sample
detection location by the at least one sensor, an edge of the
sample is moved past an edge of the at least one sensor and into
the sample detection location. Then, upon detecting the presence of
the sample in the sample detection location by the at least one
sensor, the edge of the sample is moved past the edge of the at
least one sensor and out of the sample detection location.
Additionally, between oscillations, data may be collected by one or
more sensors. By repeating these steps, an accumulation of material
on or about the at least one sensor may be prevented.
Inventors: |
Widrig Opalsky, Cindra A.;
(Ottawa, CA) ; Opalsky, David; (Ottawa, CA)
; Maczuszenko, Andy; (Etobicoke, CA) ; Lauks,
Imants R.; (Rockcliffe Park, CA) |
Correspondence
Address: |
Patent Administrator
KATTEN MUCHIN ZAVIS ROSENMAN
Suite 1600
525 West Monroe Street
Chicago
IL
60661-3693
US
|
Assignee: |
i-STAT Corporation
|
Family ID: |
22664737 |
Appl. No.: |
10/189729 |
Filed: |
July 8, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10189729 |
Jul 8, 2002 |
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09528238 |
Mar 17, 2000 |
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6438498 |
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60181544 |
Feb 10, 2000 |
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Current U.S.
Class: |
702/25 |
Current CPC
Class: |
B01L 2400/0478 20130101;
B01L 2200/143 20130101; B01L 2400/0439 20130101; B01L 3/502746
20130101; B01L 2200/0605 20130101; B01L 2200/0673 20130101; B01L
2400/0406 20130101; B01L 2400/0415 20130101; B01L 2300/0645
20130101; B01L 2400/0688 20130101; B01L 2200/14 20130101; G01N
33/4905 20130101; B01L 2400/0481 20130101; B01L 2300/0816 20130101;
B01L 2300/0867 20130101; B01L 2300/087 20130101; B01L 2400/0487
20130101; B01L 3/5027 20130101; G01N 11/04 20130101 |
Class at
Publication: |
702/25 |
International
Class: |
G01N 031/00 |
Claims
What we claim is:
1. A method of using a sample analyzing device having a sample
retaining area for holding a sample and at least one sensor located
at least partially within said sample retaining area, said at least
one sensor having at least one edge which defines a sample
detection location, said at least one sensor further being capable
of detecting a presence or an absence of the sample in said sample
detection location, said method comprising the steps of: (a)
introducing the sample into said sample retaining area; (b) mixing
a reagent with the sample to commence formation of a reagent
product; (c) upon detecting the absence of the sample from the
sample detection location by said at least one sensor, moving an
edge of the sample past an edge of the at least one sensor into
said sample detection location so that at least a given portion of
the sample is located therein; (d) upon detecting the presence of
the sample in the sample detection location by said at least one
sensor, moving the edge of the sample past the edge of the at least
one sensor and out of said sample detection location so that less
than the given portion of the sample is located therein; and (e)
preventing an accumulation of material on or about said at least
one sensor by repeating steps (c)-(d) until passage of a
predetermined period.
2. The method of claim 1, wherein said at least one sensor
comprises two electrodes, wherein said at least one sensor detects
the presence of the sample when the sample contiguously covers both
electrodes, and wherein said at least one sensor detects the
absence of the sample when the sample does not contiguously cover
both electrodes.
3. The method of claim 1, wherein said reagent comprises a liquid
or a solid reagent.
4. The method of claim 1, wherein said at least one sensor
comprises an electrochemical sensor.
5. The method of claim 4, wherein said electrochemical sensor
comprises at least one of an amperometric sensor, a potentiometric
sensor, or a conductivity sensor.
6. The method of claim 1, wherein said sample analyzing device
further comprises another sensor for collecting data from the
sample, said method further comprising: collecting data by said
another sensor when the sample is moved into said sample detection
location; repeating steps (c)-(d) until a sufficient predetermined
transformation of the sample is detected from said collected data;
extracting reagent product information from said collected data;
and calculating a transformation time by utilizing said extracted
reagent product information.
7. The method of claim 6, wherein said another sensor comprises an
electrochemical sensor.
8. The method of claim 7, wherein said electrochemical sensor
comprises an amperometric sensor or a potentiometric sensor.
9. The method of claim 6, wherein the predetermined transformation
comprises a chemical or physical change.
10. The method of claim 6, wherein the sample comprises blood,
wherein the transformation comprises at least a partial formation
of a blood clot, and wherein the reagent product information
comprises a clot curve, and the transformation time comprises a
clot time.
11. The method of claim 6, wherein said another sensor comprises an
amperometric sensor capable of applying a potential and measuring a
current, and wherein said collecting by said another sensor further
comprises the step of collecting said data during a real-time
formation of a clot in the sample by detecting a rise and then a
leveling off of said amperometric sensor current.
12. The method of claim 6, wherein said another sensor is capable
of applying a potential and measuring a current and wherein said
step of collecting data by said another sensor comprises: holding
voltage on said another sensor at approximately about -50 mV for
approximately about two and one half seconds; holding voltage on
said another sensor at approximately about 100 mV for approximately
about six-tenths of a second; sampling said another sensor for a
predetermined sampling period, thereby collecting data on the
sample at a single instance and creating a data point; and storing
said collected data concerning said data point.
13. The method of claim 12, wherein said predetermined sampling
period falls in the range of about 0.01 to about 0.07 seconds.
14. The method of claim 6, wherein said reagent product information
comprises clot curve information, and wherein extracting reagent
product information from said collected data comprises obtaining a
rise time, a maximum slope, and a change in current between a
baseline and an upper shoulder, wherein said baseline is defined as
a trend line drawn through a portion of an amperometric waveform
occurring before a current rise, wherein said shoulder is defined
as occurring when a slope of a clot curve drops to a predetermined
level, and wherein said rise time is defined as a time at which a
current rises to a halfway point between said baseline and said
upper shoulder.
15. The method of claim 14, wherein said predetermined level
defining said shoulder is approximately about 40% to about 60% of
said maximum slope.
16. The method of claim 6, wherein said another sensor comprises an
amperometric sensor capable of applying a potential and measuring a
current, wherein the sample comprises blood, wherein the
transformation comprises formation of a blood clot, wherein the
reagent product information comprises a clot curve, and wherein
extracting reagent product information from said data further
comprises the steps of: determining a maximum current; comparing
said maximum current with expected limits, and reporting an error
result and terminating said method if said maximum current is not
within said expected limits; determining a minimum current;
comparing said minimum current with said expected limits, and
reporting an error result and terminating said method if said
minimum current is not within said expected limits; determining a
baseline, wherein said baseline is defined as a trend line drawn
through a portion of an amperometric waveform occurring before a
current rise; comparing said baseline with said expected limits,
and reporting an error result and terminating said method if said
baseline is not within said expected limits; comparing said maximum
current with said minimum current, wherein an absence of clot
formation is reported if said maximum current is found earlier in
time than said minimum current; determining an amplitude and a time
of a maximum slope; comparing said amplitude and said time of said
maximum slope with said expected limits, and reporting an error
result and terminating said method if said amplitude and said time
of said maximum slope are not within said expected limits;
determining a time, if any, where a slope of a clot curve decays to
50% of a maximum clot curve slope, said time indicating an
occurrence of a shoulder, and recording a current at said time and
said time itself, terminating said method and reporting an absence
of clot formation if no shoulder is found; determining an idelta by
subtracting a baseline current from a shoulder current; comparing
said idelta with said expected limits, and, if said idelta is not
within said expected limits, comparing said idelta with a clot
detection limit, and reporting an error result and terminating said
method if said idelta is not within said expected limits and not
below a clot detection limit, and reporting an absence of a clot
formation and terminating said method if said idelta is not within
said expected limits but below a clot detection limit; determining
a rise time, wherein said rise time is defined as a time at which
said current rises to a halfway point between said baseline and an
upper shoulder; and comparing said rise time with said expected
results, and reporting an error result if said rise time is not
within said expected limits.
17. The method of claim 6, wherein said transformation comprises
formation of a blood clot, and wherein said calculating said
transformation time comprises utilizing time, slope and
amplitude.
18. The method of claim 6, wherein said device further comprises a
pump for moving the sample and wherein said at least one sensor is
capable of measuring conductivity, said method further comprising
the additional steps of: moving the sample forward when
conductivity measured at said at least one sensor is less than a
predetermined minimum; moving the sample backward when conductivity
measured at said at least one sensor is greater than a
predetermined maximum; and repeating said moving steps until a
sensor data point is recorded by said another sensor.
19. The method of claim 6, further comprising eliminating any
effects of motion on said another sensor by synchronizing movement
of the sample with data collection by said another sensor.
20. The method of claim 6, further comprising collecting data from
a reagent rich portion of the sample by reciprocatingly moving the
sample over said another sensor.
21. The method of claim 6, wherein the detection of said
transformation comprises the detection of a real time formation of
at least one clot.
22. The method of claim 6, wherein said another sensor is capable
of measuring a current and wherein said collecting data by said
another sensor comprises: holding voltage on said another sensor at
approximately about -45 to about -55 mV for approximately about 2.5
to about 2.6 seconds; holding voltage on said another sensor at
approximately about 95 to about 105 mV for approximately about 0.5
to about 0.6 seconds; sampling said another sensor for
approximately about 0.01 to about 0.07 seconds, thereby collecting
data on the sample at a single instance and creating a data point;
and storing said collected data concerning said data point.
23. The method of claim 6, further comprising, prior to an initial
data sampling, setting an electrode potential of said another
sensor to a level that causes electrochemical activity of the
sample to remain at a predetermined minimum.
24. The method of claim 6, wherein a Faradaic component of the
collected data is maximized by imposing a time delay before
collecting data.
25. The method of claim 6, wherein electrochemical contamination of
said another sensor is prevented by varying an electrode potential
of said another sensor between each instance of data
collection.
26. The method of claim 1, wherein said mixing step (b) occurs in
said sample retaining area and comprises dissolving the reagent
into the sample by repeatedly moving the sample into and out of
said sample detection location.
27. The method of claim 1, wherein the step of mixing the sample
with the reagent comprises repeatedly moving the sample so that an
edge of the sample moves past an edge of said at least one sensor
and into said sample detection location followed by moving the
sample so that the edge of the sample moves back past the edge of
said at least one sensor and out of said sample detection
location.
28. The method of claim 1, wherein said mixing step (b) comprises
moving the sample into said sample detection location when the
sample is determined to be absent from said sample detection
location by said at least one sensor, and moving the sample out of
said sample detection location when the sample is determined to be
present in said sample detection location by said at least one
sensor.
29. The method of claim 1, wherein said device has a reagent mixing
area formed in said sample retaining area, and wherein said mixing
step (b) comprises repeated reciprocating movement through said
reagent mixing area of only a first portion of the sample whereby
movement of a remainder of the sample occurs in said sample
retaining area outside of said reagent mixing area, wherein after
said mixing, said first portion has a higher reagent concentration
than that of said remainder.
30. The method of claim 29, wherein said sample analyzing device
further comprises another sensor capable of collecting data from
the sample, said method further comprising collecting data from the
sample by said another sensor only from said first portion of the
sample.
31. The method of claim 29, wherein the reagent is initially
located in said reagent mixing area.
32. The method of claim 29, wherein the reagent is introduced into
said reagent mixing area during said mixing step (b).
33. The method of claim 1, wherein said movement in said moving
steps (c) and (d) commences a predetermined amount of time after
detection of the presence or absence of the sample in said sample
detection location.
34. The method of claim 1, wherein said movement in said moving
steps (c) and (d) commences substantially immediately after
detection of the presence or absence of the sample in said sample
detection location.
35. The method of claim 1, wherein the reagent is a substrate for
an enzyme in a coagulation cascade, wherein the reagent product is
an electroactive species, and wherein said material to be prevented
from accumulating comprises at least one or more adsorbable
components of the sample or a dried form of the sample.
36. A method of using a sample analyzing device having a sample
retaining area for holding a sample and at least one sensor having
a sensing surface located at least partially within said sample
retaining area, said at least one sensor being capable of detecting
a presence of the sample when the sample is in contact with the
sensing surface and of detecting an absence of the sample when the
sample is not in contact with the surface, said method comprising
the steps of: (a) introducing the sample into said sample retaining
area; and either or both of steps (b) and (c); (b) mixing a reagent
by moving an air-liquid boundary of the sample through a reagent
mixing region of said sample retaining area until the reagent is at
least substantially dissolved in a vicinity of the air liquid
boundary of the sample to form a reagent rich portion of the
sample; and (c) preventing an accumulation of material on said
sensing surface by moving an air-liquid boundary of the sample over
said sensing surface until completion of a sample analysis; wherein
said reciprocating movement comprises moving the sample toward the
sensing surface until the sensor detects the presence of the
sample, and moving the sample away from the sensing surface until
the sensor detects the absence of the sample.
37. A computer readable medium storing instructions for using a
sample analyzing device having a sample retaining area for holding
a sample and at least one sensor located at least partially within
said sample retaining area, said at least one sensor having at
least one edge which defines a sample detection location, said at
least one sensor further being capable of detecting a presence or
an absence of the sample in said sample detection location, said
instructions being executable by a computer and comprising the
steps of: (a) introducing the sample into said sample retaining
area; (b) mixing a reagent with the sample to commence formation of
a reagent product; (c) upon detecting the absence of the sample
from the sample detection location by said at least one sensor,
moving an edge of the sample past an edge of the at least one
sensor into said sample detection location so that at least a given
portion of the sample is located therein; (d) upon detecting the
presence of the sample in the sample detection location by said at
least one sensor, moving the edge of the sample past the edge of
the at least one sensor and out of said sample detection location
so that less than the given portion of the sample is located
therein; and (e) preventing an accumulation of material on or about
said at least one sensor by repeating steps (c)-(d) until passage
of a predetermined period.
38. A computer readable medium storing instructions for using a
sample analyzing device having a sample retaining area for holding
a sample and at least one sensor having a sensing surface located
at least partially within said sample retaining area, said at least
one sensor being capable of detecting a presence of the sample when
the sample is in contact with the sensing surface and of detecting
an absence of the sample when the sample is not in contact with the
surface, said instructions being executable by a computer and
comprising the steps of: (a) introducing the sample into said
sample retaining area; and either or both of steps (b) and (c); (b)
mixing a reagent by moving an air-liquid boundary of the sample
through a reagent mixing region of said sample retaining area until
the reagent is at least substantially dissolved in a vicinity of
the air liquid boundary of the sample to form a reagent rich
portion of the sample; and (c) preventing an accumulation of
material on said sensing surface by moving an air-liquid boundary
of the sample over said sensing surface until completion of a
sample analysis; wherein said reciprocating movement comprises
moving the sample toward the sensing surface until the sensor
detects the presence of the sample, and moving the sample away from
the sensing surface until the sensor detects the absence of the
sample.
39. A system for analyzing a sample and usable with a computer,
comprising: a sample analyzing device having a sample retaining
area for holding a sample and at least one sensor located at least
partially within said sample retaining area, said at least one
sensor having at least one edge which defines a sample detection
location, said at least one sensor further being capable of
detecting a presence or an absence of the sample in said sample
detection location; and a memory medium readable by the computer
and storing computer instructions, the instructions comprising the
steps of: (a) introducing the sample into said sample retaining
area; (b) mixing a reagent with the sample to commence formation of
a reagent product; (c) upon detecting the absence of the sample
from the sample detection location by said at least one sensor,
moving an edge of the sample past an edge of the at least one
sensor into said sample detection location so that at least a given
portion of the sample is located therein; (d) upon detecting the
presence of the sample in the sample detection location by said at
least one sensor, moving the edge of the sample past the edge of
the at least one sensor and out of said sample detection location
so that less than the given portion of the sample is located
therein; and (e) preventing an accumulation of material on or about
said at least one sensor by repeating steps (c)-(d) until passage
of a predetermined period.
40. A system for analyzing a sample and useable with a computer,
comprising: an analyzing device having a sample retaining area for
holding a sample and at least one sensor having a sensing surface
located at least partially within said sample retaining area, said
at least one sensor being capable of detecting a presence of the
sample when the sample is in contact with the sensing surface and
of detecting an absence of the sample when the sample is not in
contact with the surface; and a memory medium readable by the
computer and storing computer instructions, the instructions
comprising the steps of: (a) introducing the sample into said
sample retaining area; and either or both of steps (b) and (c); (b)
mixing a reagent by moving an air-liquid boundary of the sample
through a reagent mixing region of said sample retaining area until
the reagent is at least substantially dissolved in a vicinity of
the air liquid boundary of the sample to form a reagent rich
portion of the sample; and (c) preventing an accumulation of
material on said sensing surface by moving an air-liquid boundary
of the sample over said sensing surface until completion of a
sample analysis; wherein said reciprocating movement comprises
moving the sample toward the sensing surface until the sensor
detects the presence of the sample, and moving the sample away from
the sensing surface until the sensor detects the absence of the
sample.
41. A method for calculating a sample transformation time by
utilizing a device comprising a sample retaining area and a sensor
located at least partially within the sample retaining area to form
a data collection region, wherein data is collected from the sample
when the sample is moved into said data collection region, said
method comprising the steps of: (a) introducing the sample into
said device; (b) mixing a reagent with the sample to commence
formation of a reagent product and transformation of the sample;
(c) moving the sample into said data collection region; (d)
collecting data by said sensor when the sample is moved into said
data collection region; (e) moving the sample out of said data
collection region; (f) repeating steps (c)-(e) until a sufficient
predetermined transformation is detected from said data collected
in said step (d); (g) extracting reagent product information from
said data collected in said collecting step (d); (h) calculating
the transformation time by utilizing said reagent product
information extracted in said extracting step (g); and wherein said
movement steps (c) and (e) prevent the accumulation of material on
or about said sensor.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a system, method and
computer implemented process for conducting a variety of assays.
More particularly, the instant invention relates to a system,
method and computer implemented process for use in analyzing fluid
samples. The invention relates even more particularly to
calculating or collecting a sample transformation time or any of a
variety of sample information by moving a sample over a sensor,
during data collection, to dissolve a reagent or to prevent the
accumulation of unwanted material on or about the sensor
surface.
BACKGROUND OF THE INVENTION
[0002] Numerous procedures and techniques exist for analyzing and
testing blood and other body fluids. To name one, coagulation
techniques may be used to collect a wide variety of information
from given samples of blood. While some of these procedures are
relatively simple, others can be more sophisticated and require
multiple steps or preparations. For instance, many procedures
involving blood samples require the addition of reagents to
commence the formation of clots or other steps to prepare the
sample for data collection and to account for the unique
characteristics of blood.
[0003] For example, keeping blood in a fluid state, termed
hemostasis, requires a subtle balance of pro- and anticoagulants.
In the human body, procoagulants prevent excessive bleeding by
blocking blood flow from a damaged vessel, whereas anticoagulants
prevent clots from forming in the circulating system which could
otherwise block blood vessels and lead to myocardial infarction or
stroke.
[0004] The biochemical sequence leading to a blood clot is termed
the coagulation cascade. This mechanism is based on catalytic
conversion of fibrinogen, a soluble plasma protein, to insoluble
fibrin. The enzyme catalyzing this reaction is thrombin, which does
not permanently circulate in the blood in an active form but exists
as prothrombin, the inactive precursor of thrombin. Conversion to
thrombin occurs in the presence of calcium ions and tissue
thromboplastin. This mechanism is known as the extrinsic pathway. A
second, more complex, intrinsic pathway is activated by clotting
factors associated with platelets.
[0005] Diagnosis of hemorrhagic conditions such as hemophilia,
where one or more of the twelve blood clotting factors may be
defective, can be achieved by a wide variety of coagulation tests.
In addition, several tests have been developed to monitor the
progress of thrombolytic therapy. Other tests have been developed
to signal a prethrombolytic or hypercoagulable state, or to monitor
the effect of administering protamine to patients during
cardiopulmonary bypass surgery. However, the main value of
coagulation tests is in monitoring oral and intravenous
anticoagulation therapy. Three of the key diagnostic tests are
activated partial thromboplastin time (APTT), prothrombin time
(PT), and activated clotting time (ACT).
[0006] An APTT test evaluates the intrinsic and common pathways of
coagulation. For this reason APTT is often used to monitor
intravenous heparin anticoagulation therapy. Specifically, it
measures the time for a fibrin clot to form after the activating
agent, calcium, and a phospholipid have been added to the citrated
blood sample. Heparin administration has the effect of suppressing
clot formation.
[0007] A PT test evaluates the extrinsic and common pathways of
coagulation and, therefore, is used to monitor oral anticoagulation
therapy. The oral anticoagulant coumadin suppresses the formation
of prothrombin. Consequently, this test is based on the addition of
calcium and tissue thromboplastin to the blood sample.
[0008] An ACT test evaluates the intrinsic and common pathways of
coagulation. It is often used to monitor anticoagulation via
heparin therapy. The ACT test is based on addition of an activator
to the intrinsic pathway to fresh whole blood to which no exogenous
anticoagulant has been added.
[0009] The standard laboratory technology for coagulation tests
typically uses a turbidimetric method. For analysis, whole-blood
samples are collected into a citrate vacutainer and then
centrifuged. The assay is performed with plasma to which a
sufficient excess of calcium has been added to neutralize the
effect of citrate. For a PT test, tissue thromboplastin is provided
as a dry reagent that is reconstituted before use. This reagent is
thermally sensitive and is maintained at 4 degrees C. Aliquots of
sample and reagent are transferred to a cuvette heated at 37
degrees C., and the measurement is made based on a change in
optical density.
[0010] As an alternative to the turbidimetric method, Beker et al.
(See, Haemostasis (1982) 12:73) introduced a chromogenic PT reagent
(Thromboquant PT). The assay is based on the hydrolysis of
p-nitroaniline from a modified peptide, Tos-Gly-Pro-Arg-pNA, by
thrombin and is monitored spectrophotometrically.
[0011] Coagulation monitors are known for the analysis of whole
blood. For example, a unit-use cartridge has been described in U.S.
Pat. No. 4,756,884 in which dry reagents are placed into the
analyzer which is then heated to 37 degrees C. before a drop of
blood is introduced. The sample is mixed with the reagent by
capillary draw. The detection mechanism is based on laser light
passing through the sample. Blood cells moving along the flow path
yield a speckled pattern specific to unclotted blood. When the
blood clots, movement ceases producing a pattern specific to
clotted blood.
[0012] An automatic coagulation timer has been described which
measures the activated clotting time (ACT) in blood samples from
patients during cardiopulmonary bypass. The sample is added to a
cartridge which incorporates a stirring device onto which the clot
forms. Motion of the stirring device is controlled by a photo
optical detector (See, Keeth et al., Proceedings Am. Acad.
Cardiovascular Perfusion (1988) 9:22).
[0013] U.S. Pat. No. 4,304,853 discloses the use of a substrate
which produces an electroactive product on reaction with the enzyme
thrombin. A sensor is used to detect the electroactive product. The
disclosure does not include a single-use cartridge and does not
disclose the use of a second sensor to monitor the location of the
sample.
[0014] U.S. Pat. No. 4,497,744 discloses a turbidometric method for
assaying coagulation. Plasma containing an excess of citrate is
used in the test. A reagent which induces clotting is added, the
sample is placed in a turbidometer, and coagulation is indicated by
an increase in the turbidity of the sample.
[0015] U.S. Pat. No. 5,096,669, incorporated herein by reference,
includes the general format for use of a cartridge and analytzer
for blood chemistry testing such as potassium and glucose blood
levels and the use of a pump to move a sample fluid to a sensor
region in a single direction.
[0016] U.S. Pat. No. 5,200,051, incorporated herein by reference,
discloses efficient methods of microfabrication of sensor devices
for analysis of analytes.
[0017] U.S. Pat. No. 5,302,348 discloses a blood coagulation test
apparatus in which blood is forced to traverse a capillary conduit.
When the time for traverse exceeds the previous time by a certain
percentage, coagulation is deemed to have occurred. The apparatus
includes an unclosed entry port which is connected to two conduits,
the first receiving the sample to be assayed, the second receiving
overflow sample.
[0018] U.S. Pat. Nos. 5,447,440 and 5,628,961, both incorporated
herein by reference, disclose a single-use cartridge and reader
used in coagulation assays. The condition of the sample is
determined by its flow properties as detected, for example, by a
conductivity sensor.
[0019] U.S. Pat. No. 5,526,111 discloses a method for calculating a
coagulation characteristic of a sample of blood, a blood fraction,
or a control. This method uses a backwards looking approach to
determine a slope of an envelope at each of a number of stored
envelope values from which the coagulation characteristic is
determined. However, this method uses a fixed or predetermined
sampling time and rectifies stored sample values to provide its
envelope values. In addition, this method requires storing the
envelope values as well as the sampled signal values.
[0020] U.S. Pat. Nos. 5,916,522 and 5,919,711 disclose a device
which uses ion-specific electrodes to measure ionic activity of
fluids including bodily fluids. The fluids are metered and
transported within the device by centrifugation and pressurization
of the device.
[0021] As evident from the above discussion, the majority of blood
tests require the addition and dissolution of some sort of reagent
into the sample before data collection can commence. Thus, a need
exists for a system, method, and computer implemented process which
can be used to efficiently and effectively introduce and dissolve a
reagent into a sample. Furthermore, as generally true with other
types of medical procedures, the speed and time required to
complete the tests are of paramount importance. Thus, a need exists
also for a system and method which can dissolve or distribute a
reagent into a blood sample in a relatively short amount of
time.
[0022] Also, the compactness and smaller physical size of today's
testing devices has directly resulted in limits on the amount of
reagent which may be stored in a sampling device. Consequently, a
need exists for a system, method, and computer implemented process
which can make use of a limited amount of reagent without placing
restrictions on the amount of blood to be sampled. In this manner,
a relatively small amount of reagent may be used with samples of
any volume. On a related note, in situations where limited amounts
of reagent are dissolved in relatively larger amounts of sample, a
need also exists for a system, method and computer implemented
process which is capable of collecting data from only those
portions of sample containing the highest amounts of reagent.
[0023] In addition, since data collection can be adversely affected
by the accumulation of undesirable material contained in blood--a
problem familiar to those skilled in the art of collecting
electrical and electrochemical measurements in biological fluids, a
need exists also for a method, system and computer implemented
process which is capable of preventing such an accumulation in the
data collection region of the analyzing device.
SUMMARY OF THE INVENTION
[0024] Thus, to address these and other needs of the prior art, it
is an object of the present invention to provide a novel system,
method and computer implemented process for use in analyzing fluid
samples by, for example, reciprocatingly and repeatedly moving a
sample over a sensor for purposes of calculating a sample
transformation time.
[0025] It is also an object of the present invention to provide a
technique which can be used to efficiently and effectively mix and
dissolve a reagent into a sample.
[0026] It is another object of the present invention to provide a
technique which can dissolve or distribute a reagent into a fluid
sample in a relatively short amount of time.
[0027] It is yet another object of the present invention to provide
a technique which can make use of a limited amount of reagent
without placing restrictions on the amount of fluid to be
sampled.
[0028] It is still another object of the present invention to
provide a technique which is capable of collecting data from only
those portions of sample containing the highest amounts of
reagent.
[0029] Further yet, it is another object of the present invention
to provide a technique which is capable of preventing an
accumulation of unwanted material in a data collection region of an
analyzing device.
[0030] To meet these and other objects, the present invention
contemplates providing a method, system and computer readable
medium storing instructions for using a sample analyzing device
having a sample retaining area for holding a sample and at least
one sensor located at least partially within the sample retaining
area. In this embodiment, the at least one sensor has at least one
edge which defines a sample detection location and is capable of
detecting a presence or an absence of the sample in the sample
detection location. The invention further includes: (a) introducing
the sample into the sample retaining area; (b) mixing a reagent
with the sample to commence formation of a reagent product; (c)
upon detecting the absence of the sample from the sample detection
location by the at least one sensor, moving an edge of the sample
past an edge of the at least one sensor into the sample detection
location so that at least a substantial portion of the sample is
located therein; (d) upon detecting the presence of the sample in
the sample detection location by the at least one sensor, moving
the edge of the sample past the edge of the at least one sensor and
out of the sample detection location so that less than a
substantial portion of the sample is located therein; and (e)
preventing an accumulation of material on or about the at least one
sensor by repeating steps (c)-(d) until passage of a predetermined
period.
[0031] In another embodiment, the present invention contemplates
providing a system, method and computer readable medium storing
instructions for using a sample analyzing device having a sample
retaining area for holding a sample and at least one sensor having
a sensing surface located at least partially within the sample
retaining area. In this embodiment, the at least one sensor is
capable of detecting a presence of the sample when the sample is in
contact with the sensing surface and of detecting an absence of the
sample when the sample is not in contact with the surface. This
embodiment further includes: (a) introducing the sample into the
sample retaining area; and at least one of steps (b) and (c); (b)
mixing a reagent by moving an air-liquid boundary of the sample
through a reagent mixing region of the sample retaining area until
the reagent is at least substantially dissolved in a vicinity of
the air liquid boundary of the sample to form a reagent rich
portion of the sample; and (c) preventing an accumulation of
material on the sensing surface by moving an air-liquid boundary of
the sample over the sensing surface until completion of a sample
analysis; and wherein the reciprocating movement includes moving
the sample toward the sensing surface until the sensor detects the
presence of the sample, and moving the sample away from the sensing
surface until the sensor detects the absence of the sample.
[0032] In yet another embodiment, the present invention
contemplates providing a system, method and computer readable
medium storing instructions for calculating a sample transformation
time by utilizing a device comprising a sample retaining area and a
sensor located at least partially within the sample retaining area
to form a data collection region. In this embodiment, the data is
collected from the sample when the sample is moved into the data
collection region. This embodiment further includes: (a)
introducing the sample into the device; (b) mixing a reagent with
the sample to commence formation of a reagent product and
transformation of the sample; (c) moving the sample into the data
collection region; (d) collecting data by the sensor when the
sample is moved into the data collection region; (e) moving the
sample out of the data collection region; (f) repeating steps
(c)-(e) until a sufficient predetermined transformation is detected
from the data collected in step (d); (g) extracting reagent product
information from the data collected in the collecting step (d); (h)
calculating the transformation time by utilizing the reagent
product information extracted in the extracting step (g); and
wherein the movement steps (c) and (e) prevent the accumulation of
material on or about the sensor.
[0033] There has thus been outlined, rather broadly, the more
important features of the invention in order that the detailed
description thereof that follows may be better understood, and in
order that the present contribution to the art may be better
appreciated. There are, of course, additional features of the
invention that will be described hereinafter and which will form
the subject matter of the claims appended hereto.
[0034] In this respect, before explaining at least one embodiment
of the invention in detail, it is to be understood that the
invention is not limited in its application to the details of
construction and to the arrangements of the components set forth in
the following description or illustrated in the drawings. The
invention is capable of other embodiments and of being practiced
and carried out in various ways. Also, it is to be understood that
the phraseology and terminology employed herein are for the purpose
of description and should not be regarded as limiting.
[0035] As such, those skilled in the art will appreciate that the
conception, upon which this disclosure is based, may readily be
utilized as a basis for the designing of other structures, methods
and systems for carrying out the several purposes of the present
invention. It is important, therefore, that the claims be regarded
as including such equivalent constructions insofar as they do not
depart from the spirit and scope of the present invention.
[0036] Further, the purpose of the foregoing abstract is to enable
the U.S. Patent and Trademark Office and the public generally, and
especially the scientists, engineers and practitioners in the art
who are not familiar with patent or legal terms or phraseology, to
determine quickly from a cursory inspection the nature and essence
of the technical disclosure of the application. The abstract is
neither intended to define the invention of the application, which
is measured by the claims, nor is it intended to be limiting as to
the scope of the invention in any way.
[0037] These together with other objects of the invention, along
with the various features of novelty which characterize the
invention, are pointed out with particularity in the claims annexed
to and forming a part of this disclosure. For a better
understanding of the invention, its operating advantages and the
specific objects attained by its uses, reference should be had to
the accompanying drawings and descriptive matter in which there is
illustrated preferred embodiments of the invention.
[0038] Other objects of the present invention will be evident to
those of ordinary skill, particularly upon consideration of the
following detailed description of the preferred embodiments.
NOTATIONS AND NOMENCLATURE
[0039] The detailed descriptions which follow may be presented in
terms of program procedures executed on computing or processing
systems such as, for example, a computer or network of computers.
These procedural descriptions and representations are the means
used by those skilled in the art to most effectively convey the
substance of their work to others skilled in the art.
[0040] A procedure is here, and generally, conceived to be a
self-consistent sequence of steps leading to a desired result.
These steps are those requiring physical manipulations of physical
quantities. Usually, though not necessarily, these quantities take
the form of electrical or magnetic signals capable of being stored,
transferred, combined, compared and otherwise manipulated. It
proves convenient at times, principally for reasons of common
usage, to refer to these signals as bits, values, elements,
symbols, characters, terms, numbers, or the like. It should be
noted, however, that all of these and similar terms are to be
associated with the appropriate physical quantities and are merely
convenient labels applied to these quantities.
[0041] Further, the manipulations performed are often referred to
in terms, such as adding or comparing, which are commonly
associated with mental operations performed by a human operator. No
such capability of a human operator is necessary, or desirable in
most cases, in any of the operations described herein which form
part of the present invention; the operations are machine
operations. Useful machines for performing the operation of the
present invention include general purpose digital computers or
similar devices.
BRIEF DESCRIPTION OF THE FIGURES
[0042] FIG. 1 depicts a cross-sectional plan view of one example of
a system capable of implementing and utilizing the techniques of
the present invention;
[0043] FIG. 2 depicts a cross section of a sample entry port of the
system of FIG. 1;
[0044] FIG. 3 depicts a cross section of a sample retaining area of
the system of FIG. 1;
[0045] FIG. 4 depicts a perspective view of an overflow chamber of
the system of FIG. 1;
[0046] FIG. 5 depicts a conductimetric and amperometric sensor of
the system of FIG. 1;
[0047] FIGS. 6A-6C depict an oscillating movement of a sample in an
analysis location of the system of FIG. 1;
[0048] FIG. 7 depicts an example of an overview of a coagulation
procedure implementable by the system of FIG. 1;
[0049] FIG. 8 depicts a data collection step of the procedure of
FIG. 7;
[0050] FIGS. 9A-9C depict an information extraction step of the
procedure of FIG. 7;
[0051] FIG. 10 depicts yet another example of a system capable of
implementing and utilizing the techniques of the present
invention;
[0052] FIG. 11 depicts a block diagram representation of the major
components of the system of FIG. 10; and
[0053] FIG. 12 depicts an example of a memory medium readable by
the computing system of FIG. 10 and of storing computer
instructions, in accordance with the principles of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0054] In accordance with the principles of the present invention,
a method, system and computer readable medium for using a sample
analyzing device are disclosed. More particularly, the present
invention includes using a sample analyzing device which has a
sample retaining area formed therein and at least one sensor
located at least partially within the sample retaining area. The
sensor, in turn, is capable of detecting a presence or an absence
of the sample within a sample detection location defined by the
sensor edges. Advantageously, the present invention includes mixing
a reagent by moving an air-liquid boundary, or edge, of the sample
through a reagent mixing region of the sample retaining area to
dissolve the reagent within the vicinity of the air-liquid
boundary. Additionally, the present invention also includes
preventing the accumulation of material on or about the sensor by
moving, upon detection of the absence of the sample from the sample
detection location, an edge of the sample past an edge of the
sensor and into the sample detection location. Similarly, upon
detection of the presence of the sample in the sample detection
location, the invention includes moving the edge of the sample back
past the edge of the sensor and out of the sample detection
location. Thus, in the above manner, various tests, for instance
blood coagulation tests or immunoassays, may be efficiently and
effectively performed.
[0055] In accordance with the principles of the present invention,
one example of a system capable of implementing and utilizing the
present invention is depicted in FIG. 1. Furthermore, in addition
to the example depicted in FIG. 1, the techniques of the present
invention are flexible enough so that they may be implemented and
utilized in numerous other devices. For instance, U.S. Pat. Nos.
5,628,961; 5,447,440; and 5,096,669; and U.S. Provisional
Application No. 60/164,935, all of which are incorporated herein by
reference, are directed to various devices for assaying viscosity
changes in fluid samples and for performing real time fluid tests,
and serve as other examples capable of implementing and utilizing
the techniques of the present invention.
[0056] Referring to FIG. 1, a cross sectional view of a cartridge
or housing 10 implemented according to the principles of the
present invention is depicted. A sample entry port 12 allows
introduction of a sample into the housing and is surrounded by a
circumferential excess sample well 14. A snap cover 38 encloses the
sample entry port 12 with the formation of an air-tight seal.
Fluidically connected to the sample entry port 12, at one end, is a
sample holding chamber or sample retaining area 20. Located at the
other end of the sample retaining area 20 is a capillary stop 22. A
pre-sensor channel 24 leads from the capillary stop 22 to an
analysis location 31. In addition, a hydrophobic layer 26 is
positioned between the pre-sensor channel 24 and the analysis
location 31. A reagent and/or a substrate 30 may be deposited or
introduced into the system at analysis location 31. Although the
reagent 30 is depicted as being downstream of sensors 28 and 29, it
is possible to position the reagent 30 upstream of sensors 28 and
29 so that a sample passes through the reagent 30 before reaching
the sensors. Furthermore, in communication with the analysis
location 31 are one or more conductimetric sensors 28, one or more
amperometric sensors 29, and one or more reference sensors 32. Also
in communication with the analysis location 31 is a waste tube
34.
[0057] A sample may be moved within the system through use of a
flexible diaphragm pump 36. Pump 36 facilitates movement of the
sample by pumping air throughthe air tube 18, through overflow
chamber 16, and finally into sample retaining area 20. Furthermore,
although the pump in FIG. 2 is depicted as being a flexible
diaphragm pump, any suitable pump or the like may be used, such as
piston and cylinder, electrodynamic, or sonic.
[0058] In accordance with the principles of the present invention,
FIG. 2 depicts a cross-sectional view of the sample entry port area
of the cartridge or housing 10. More specifically, a wall or tape
or film 42 is shown interposed between an upper housing 40 and a
lower housing of the cartridge. In this regard, tape 42 has an
adhesive layer on each side and adheres to the top 40 and base 44
sides of the cartridge. In this particular illustration, the sample
entry port 12 as well as the sample retaining area 20 and
circumferential well 14 are shown filled with sample 46.
[0059] FIG. 3 depicts a cross-sectional view of the conjunction of
the sample retaining area 20, the pre-sensor chamber 24, and the
capillary stop 22. As depicted in FIG. 3, sample holding chamber 20
and pre-sensor channel 24 are formed or molded respectively in base
44 and base 40. The tape 42, in turn, forms the top wall of the
sample holding chamber 20 and the bottom wall of the pre-sensor
chamber 24. Tape 42 is pierced to form a capillary bore or
through-hole 22 and functions as a capillary stop by restricting
flow between the sample holding chamber 20 and the pre-sensor
chamber 24. Although the capillary stop of FIG. 3 is a circular
bore or through-hole, other suitable shapes for the capillary stop
include rectangular and various irregular shapes. If rectangular in
shape, one example has a smallest dimension of about 100 microns to
about 400 microns. In such examples, the largest dimension of the
capillary stop is about 100 microns to about 1000 microns.
[0060] FIG. 4 depicts a perspective view of the overflow chamber
16. In particular, the overflow chamber 16 is located directly
above the sample retaining area and has a bottom wall formed by
tape 42. An orifice 48 in the tape 42 fluidically connects the
overflow chamber 16 to the sample holding chamber 20. The orifice
may be any of a circular, rectangular, or irregular shape. The
overflow chamber is constructed in the form of a box with
relatively low walls. Air tube 18 delivers air from the pump 36 to
the overflow chamber 16. The volume of the overflow chamber is in
the range of 0.2 microliters to 1 milliliter. A preferred volume of
the overflow chamber is in the range of 1 microliter to 10
microliters. The diameter of the circular orifice ranges from about
100 microns to about 1000 microns.
[0061] The capillary stop is designed to have a sufficient
resistance to stop capillary draw into the pre-sensor channel, but
not sufficient to resist sudden pressure changes that occur as the
cartridge closure is snapped shut. To reduce the force at the
capillary opening at this point, two "overflow" features are
incorporated within the cartridge. The first is the overflow well
14 in FIGS. 2 and 3. As the snap closure is shut, some excess
sample is pushed into the well rather than into the cartridge. The
second feature used to address overflow is orifice 48 or pressure
vent, depicted in FIG. 4, through which excess sample may flow into
the overflow chamber 16.
[0062] As previously discussed, the overflow chamber 16 is a low
volume chamber formed in the cartridge top side and located above
the sample retaining area, separated from the chamber by a tape 42
wall. The orifice 48 in the tape 42 allows flow of excess sample
into the overflow chamber and has a greater area than the opening
of the capillary stop. As a result, orifice 48 has a lower flow
resistance than the capillary stop mentioned above.
[0063] The overflow chamber 16 above the tape opening or orifice 48
has relatively low walls so that once sample is pushed through this
hole, it contacts the corona-treated plastic and is drawn into the
chamber. The sample displaced as the cartridge is closed is
therefore trapped within this chamber. When the air bladder is
compressed, air is forced through the air pipe 18 into the overflow
chamber 16. The high surface area to volume ratio of this region
encourages sample shear so that the air pushes a path through the
excess sample leaving the excess sample on the walls of the
overflow chamber.
[0064] FIG. 7 depicts a conductimetric sensor 28 and an
amperometric sensor 29 located on a sensor chip. This sensor chip,
in turn, is positioned at least partially within sample retaining
area 20. More specifically, sensor 28 includes two parallel bars or
electrodes which together constitute a sensor surface. The
electrodes are oriented, in this example, perpendicularly to the
length of the sample retaining area or sensor channel. In addition,
edges of the sensor surface define a sample detection location
within which sensor 29 is capable of detecting the presence or the
absence of a sample by measuring a conductivity (or alternatively
an electrical resistance) between the two electrodes. By doing so,
the sensor 28 may monitor the relative position of the fluid front.
At the extremes, an open circuit reading indicates that the fluid
has been pushed off the sensor (i.e., the sample is not
contiguously covering the electrodes) and a closed circuit reading,
on the other hand, indicates the sensor is covered with fluid
(i.e., the sample is contiguously covering the electrodes). As will
be discussed in greater detail below, movement of the sample,
forward and backward, and at a specified velocity may be controlled
through use of sensor 28.
[0065] In addition to including sensor 28, the present invention
may optionally include an amperometric or potentiometric sensor 29.
In this example, sensor 29 may be capable of applying a potential
and measuring a current through use of its antenna shaped electrode
31.
[0066] Further, although the sensors in this particular discussion
are amperometric and conductimetric sensors, other sensors, for
example, any type of electrochemical or potentiometric sensor or
the like, may be used. For example, a sensor capable of detecting
ion species such as Na.sup.+ and K.sup.+ may be used. Further,
although the sensors in the instant example are depicted as being
positioned downstream of the sample retaining area, both of sensors
28 and 29 may be located anywhere within the fluid conduit.
[0067] In the example shown in FIG. 7, a potential may be applied
to the amperometric sensor 29 with the generation of an
electrochemical signal, wherein the signal is proportional to the
concentration of the product in the fluid sample. The amperometric
sensor has an applied potential of approximately +0.4 V versus a
silver-silver chloride electrode and, in another preferred
embodiment, the amperometric sensor has an applied potential of
approximately +0.1 V versus a silver-silver chloride electrode. The
signal generated by the enzyme reaction product at approximately
+0.1 V is distinguishable from the signal generated by the
unreacted substrate at approximately +0.4 V.
[0068] Sample.
[0069] The coagulation assays commonly performed with the present
invention use, for example, a sample of blood, or a sample of a
blood derivative such as blood containing an additive or diluent,
plasma, serum, or plasma or serum containing an additive or
diluent.
[0070] Sample Introduction.
[0071] The sample may be deposited into the system through the
sample entry port 12 shown in FIGS. 1 and 2. The entry port 12 is
designed so that capillary forces draw a drop of a sample through
the port of the system and toward the sample holding chamber. In
particular, this drawing action is caused by the geometry and high
surface energy of the plastic conduit of the system. The high
surface energy is achieved with a corona treatment or equivalent
treatment, such as an ion-plasma treatment, before assembly. Once
blood reaches the sample retaining area, the geometry and
corona-treated surface of the conduit cause the blood to pass along
its length up to the capillary stop. As one example, the upper
limit of the cross-sectional area of the sample retaining area is
that which would prevent capillary draw if the system were to be
held upright as it is filled. Also in this example, the lower limit
of the cross-section is set to the sample volume required for
testing and the reproducibility required of this volume. As one
example, the sample holding chamber contains 19 microliters with a
cross-sectional area of 0.0075 cm.sup.2. In other embodiments the
volume of the metered fluid sample is in the range of 1 microliter
to 1 milliliter. A preferred volume of the metered fluid sample is
in the range of 15 microliters to 50 microliters.
[0072] Metering the Fluid Sample.
[0073] The reproducibility of the volume of sample moved into the
sensor channel for mixing may affect the reproducibility of the
final concentration of dissolved reagent in the blood. In one
embodiment, the sample, for instance blood, is initially moved into
the analysis location 31. The blood sample is then moved forward by
air from pump 36 via air pipe 18. The volume of the metered fluid
sample will be approximately the volume of the holding chamber 20
between the orifice 48 in the wall of the holding chamber and the
capillary stop 22. The volume of blood that is moved depends
primarily on the volume of blood in front of the orifice, and
secondarily on the surface area-to-volume ratio of the
sample-holding chamber. Other factors include the sample hematocrit
(the percent of the blood volume comprised of red blood cells), and
the fluid speed. These latter three parameters determine the volume
of sample that will remain on the walls of the sample retaining
area as the chamber is evacuated. The fluid will be metered most
precisely at low velocity from a chamber with a low
surface-area-to-volume ratio. The lower limit on the sample holding
chamber cross-sectional area is determined by the allowable
variation in the volume loss to shear at the necessary fluid
speed.
[0074] To fill the sample holding chamber, a sufficient capillary
draw is utilized to provide an adequate amount of sample. In
addition, a stop feature is provided to prevent a sample from
overflowing into the pre-sensor channel. As discussed above,
capillary stop 22 is formed by a small bore or through-hole in the
tape gasket 42 between overlapping sections of the sample holding
chamber 20 and the pre-sensor channel 24. The capillary stop 22
that is formed is relatively small and has, for example, a
thickness equal to that of the tape 42. Although this may decrease
the resistance of the capillary and thereby decrease its
effectiveness in stopping the fluid, it also minimizes the high
shear zone through which the sample must pass before entering the
pre-sensor channel. The low volume high-shear region minimizes the
loss of sample to the walls of the capillary and decreases the
potential for the inclusion of entrapped air segments as the back
end of the moving fluid exits the capillary region.
[0075] Movement of Sample.
[0076] To move the sample, pump 36 is activated to force air
through air pipe 18 into overflow chamber 16 to force a metered
amount of sample from the sample retaining area 20 through the
pre-sensor channel 24 and into the analysis location 31. In
addition, an even flow is effected by ensuring that the surface
energy of the conduit is equal on all of its sides (i.e., by using
materials having equivalent surface energy or by treating the
surfaces to ensure uniformity), thereby preventing the formation of
air bubbles within the sample.
[0077] Reagent.
[0078] Depending on the test or analysis to be performed, a variety
of components may be included in the reagent, some of which may
contribute to rapid redissolving of the reagent by the fluid
sample. These include a water-soluble polymer, gelatin, agarose, a
polysaccharide, polyethylene glycol, polyglycine, a saccharide,
sucrose, an amino acid, glycine, a buffer salt, sodium phosphate,
HEPES buffer, or a dye molecule. In addition materials suitable for
inducing coagulation via an extrensic pathway may be used including
celite, kaolin, diatomaceous earth, clay, silicon dioxide, ellagic
acid, natural thromboplastin, recombinant thromboplastin,
phospholipid, and mixtures thereof. Furthermore, liquid reagents as
well as solid reagents may be used. Finally, the reagent may be
initially located in the reagent area, or introduced at any
convenient time and at any desired location during testing.
[0079] Thrombin-Substrate Reaction.
[0080] In one example, the substrate used in the electrogenic assay
has an amide linkage that mimics the thrombin-cleaved amide linkage
in fibrinogen. Specifically, the substrate may be a
tosyl-glycyl-prolinyl-ar- ginyl-, H-D-phenylalanyl-pipecolyl-, or
benzyl-phenylalanyl-valyl-arginyl-- moiety attached to a
N-phenyl-p-phenylenediamine or
N-[p-methoxyphenyl-]-p-phenylenediamine moiety. Thrombin cleaves
the amide bond at the carboxy-terminus of the arginine residue or
pipecolyl residue because the bond structurally resembles the
thrombin-cleaved amide linkage in fibrinogen. The product of the
thrombinsubstrate reaction is the electrochemically inert
tosyl-glycyl-prolinyl-arginyl-, H-D-phenylalanylpipecolyl-, or
benzyl-phenylalanyl-valyl-arginyl- and the electroactive compounds
N-phenyl-p-phenylenediamine or
N-[p-methoxyphenyl-]-p-phenylenediamine. The tripeptide sequence is
used because it renders the substrate virtually non-reactive with
blood proteases other than thrombin and the reactivity of thrombin
with the arginine amide linkage in the molecule is very similar to
its reactivity with the target amide linkage in fibrinogen. When
the substrate is present in a blood or blood derivative sample,
generated thrombin simultaneously converts it and fibrinogen to
their cleavage products. The electrochemical species reaction
product may be detected by, for example, an electrochemical
sensor.
[0081] There are a wide variety of suitable electrogenic materials
which exhibit reversible or quasi-reversible electrochemical
reactions which may be assayed using the amperometric sensor of the
present system. For example, ferrocene, ferrocyanide, and other
organometallic species may be detected. Others include phenazine
derivatives. Any suitable electrogenic material may be combined
with a suitable substrate for use in assaying an enzyme. For
example, suitable electrogenic materials may be combined with a
suitable tripeptide with an arginine residue for use in determining
the presence of thrombin.
[0082] An indicator electrogenic material which is detected at a
potential different from the detection potential for the substrate
or the electrogenic product of the enzymatic reaction may be
included in the reagent. Such a second electrogenic material is
useful for standardizing the amperometric sensor. Suitable
electrogenic materials for this purpose include ferrocene,
ferrocyanide, and other organometallic species, phenazine
derivatives, N-phenyl-p-phenylenediamine and
N-[p-methoxyphenyl-]-p-phenylenediamine.
[0083] The test is termed "electrogenic" because the
electrochemically detectable species is generated to allow
determination of a rate measurement or the test endpoint. This is
similar to "chromogenic" or "fluorogenic" endpoint tests in which a
change in the light absorbing or emitting properties of a sample
indicates the rate measurement or endpoint. In a chromogenic test,
for example, the cleaved portion of the substrate molecule is
colorless when attached to the tripeptide and brightly colored when
liberated by the action of thrombin. By monitoring the wavelength
at which the free species absorbs light, the time at which active
thrombin is produced can be determined. Chromogenic APTT and PT
tests have been shown to have good correlation to traditional APTT
and PT plasma tests.
[0084] Reagent Mixing.
[0085] In accordance with the principles of the present invention,
the reagent of the system may be rapidly and efficiently mixed. In
particular, the system moves an edge or air-liquid interface of the
sample repeatedly over the reagent, advantageously promoting
reagent dissolution. More specifically, when the sensor determines
that the sample is absent from the sample detection location, the
sample and its edge are moved toward the sensor surface and into a
sample detection location (defined by an edge of the sensor).
Likewise, when the sensor determines that the sample is present in
the sample detection location, the sample and its edge are moved
away from the sensor surface and out of the sample detection
location. This procedure is repeated to create an oscillating
movement until the reagent is sufficiently dissolved.
[0086] To further illustrate reference is made to FIGS. 6A-6C. In
this example, a length of the conduit is coated with reagent 30.
Oscillating a segment of the sample over the reagent induces
convection thereby rapidly dissolving the reagent. The motion is
controlled so that the trailing edge of the blood segment
continually moves back and forth across the reagent coating.
Furthermore, the movement may occur for any amount of time and is
preferably of a length sufficient to dissolve at least a
substantial portion of the reagent. In addition, the movement may
occur immediately upon the detection of the absence or the presence
of the sample, or after a brief amount of time after detection.
[0087] FIGS. 6A-C illustrate the analysis location 31 along with
other portions of the fluid path including the pre-sensor channel
24 and the waste tube 34. As mentioned above, the reagent may be
deposited in the analysis location 31 or introduced any time after
the procedure has commenced. FIG. 6B shows sample 46 after its edge
has moved past the reagent deposit. Similarly, FIG. 6C shows the
sample 46 after its edge has been moved back over the reagent
deposit. Although the reagent 30 is shown deposited in the analysis
location 31 in FIG. 6A, it is possible to place the reagent at any
location along the entire fluid path.
[0088] Data Collection and Preventing Accumulation of Unwanted
Material on Sensor.
[0089] In accordance with the principles of the present invention,
data is collected through use of, for example, sensor 29. To
prevent accumulation of unwanted material on or about the sensor,
an edge of the sample is reciprocatingly moved repeatedly over the
sensor surface. Examples of unwanted material include biological
materials such as dried blood or blood components such as plasma,
serum, cells, proteins, other molecules, salts, etc., and/or the
physical adsorption of blood components, e.g., proteins, small
molecules, molecules containing thiol groups or anything located on
the electrode to block the surface or change its
electroactivity.
[0090] In one embodiment, the oscillation or reciprocating motion
may be at a frequency in the range of 0.2 to 10 Hertz for a period
in the range of 1 to 100 seconds. In another embodiment, the
oscillation is at a frequency in the range of about 1.5 Hertz for a
period of about 20 seconds. In yet another embodiment, the
oscillation is at a frequency of about 0.3 Hertz. To gather or
extract data, the amperometric or second sensor generates a signal
at each oscillation. In this embodiment, the amperometric sensor
determines the concentration of the product each time the sample is
oscillated past the amperometric sensor.
[0091] In this embodiment, a first amperometric sensor signal is
stored by the system and subsequent signals from the amperometric
sensor are stored and compared with the first and other stored
signals in order to determine the maximum rate of change in the
amperometric sensor signal. These data are analyzed to determine a
fixed fraction of the maximum rate of change of the amperometric
sensor signal and used to determine, for example, the coagulation
parameter of interest.
[0092] In the embodiments of the invention which use the substrates
tosyl-glycyl-prolinyl-arginyl-, H-D-phenylalanyl-pipecolyl-, or
benzyl-phenylalanyl-valyl-arginyl-moiety attached to a
N-phenyl-p-phenylenediamine or
N-[p-methoxyphenyl-]-p-phenylenediamine moiety, the intact
substrates are detected at a voltage of approximately +0.4V. The
electrogenic reaction products N-phenyl-p-phenylenediamine or
N-[p-methoxyphenyl-]-p-phenylenediamine are detected at a voltage
of approximately +0.1 V. Thus in these embodiments, the system
applies a potential to an amperometric sensor with the generation
of an electrochemical signal which is proportional to the
concentration of the substrate in the fluid sample. Also, the
system applies a potential to an amperometric sensor with the
generation of an electrochemical signal which is proportional to
the concentration of the product in the fluid sample. After
hydrolysis of the substrate by thrombin, a product is formed which
reacts at the amperometric sensor with the generation of a signal
distinguishable from the signal generated by the substrate.
[0093] It should be noted that the exact voltages used to
amperometrically detect the substrate and the product will vary
depending on the chemical structure of the substrate and product.
It is important that the difference in the voltages used to detect
the substrate and the product be large enough to prevent
interference between the readings. With some substrates, the
voltage required to electrochemically detect the substrate is so
high as to be beyond practical measurement. In these cases, it is
only necessary that the product be detectable amperometrically.
[0094] The sensors are preferably microfabricated of any suitable
electroconductive material and are preferably made of gold,
platinum, silver or iridium. It is also desirable to coat the
sensor with a thin organic layer which prevents poisoning of the
sensor surface by blood components such as a self-assembled thiol
film. Mercaptoalkanols form self-asseed thiol firms, and some
examples include mercaptoethanol, mercaptopropanol,
mercaptobutanol, and mixtures thereof.
[0095] Thus, by reciprocatingly moving the sample into contact with
the sensor and then out of contact with the sensor, the
accumulation of unwanted material on the sensor surface may be
prevented, thereby resulting in measurements that are more accurate
than previously available from the prior art.
[0096] Creating a Reagent Rich Portion in the Sample.
[0097] In accordance with the principles of the present invention,
a reagent rich portion may be created in the sample by
reciprocatingly moving only a portion of the sample through the
reagent mixing area. In this manner, because reagent need not be
dissolved in the entire sample, a relatively small amount of
reagent may be used without compromising the quality of the
performed procedure. More specifically, only a first portion of the
sample is moved through the reagent mixing area (i.e., the area
where the reagent is introduced or deposited) whereby movement of
the remainder of the sample occurs in the fluid conduit outside of
the reagent mixing area. As a result, after mixing, the first
portion of the sample has a higher reagent concentration than that
of the remainder of the sample. Advantageously, the data collected
by, for example, sensor 29 from this reagent rich first portion
yields results that are much more accurate than the results
collected from prior art methods.
[0098] Maintaining the Fluid Position.
[0099] In accordance with the principles of the invention,
quiescence may be maintained within the sample throughout the
course of the test. This is achieved through active position
control using feedback from the fluid position sensor employed to
monitor the mixing and to facilitate data collection. For short
duration tests, the resistance (or conductivity) between the bars
of the sensor is maintained within a window of a predetermined
minimum and a predetermined maximum, or in other words a set number
of ohms above the closed circuit reading, until a data point is
recorded by the system or the sensor. The sample air-liquid
interface is therefore held between the two bars. If the sample
drifts back toward the sample-holding chamber, the resistance will
decrease until a pre-set limit is triggered causing the system to
push the sample forward until the control resistance is again
achieved. If the sample drifts toward the waste tube, the
resistance will increase causing the system to pull the sample
backwards. With the present invention, the fluid front can be
maintained within 100 microns of a nominal position. In addition,
the movements are of a low enough amplitude and speed as to avoid
convection within the sample.
[0100] The position control feature of the present invention may
advantageously be used in conjunction with the accumulation
prevention feature to produce exceptional results. For instance,
with coagulation tests that require lengthy amounts of time to
produce an endpoint, for example 15 minutes, red blood cells or
other unwanted material may settle or blood components may dry on
or about the sensor surface. These conditions can cause the
resistance for a given fluid position to increase and interfere
with the position controller. In the case of settling, the
resistance can gradually increase causing the controller to respond
as though the fluid has drifted forward causing inaccurate
results.
[0101] To circumvent these problems, the fluid is periodically
moved to the fully closed circuit position where the closed circuit
resistance is measured. The fluid is then repositioned at a
resistance value offset relative to the new closed circuit reading.
This oscillation continually wets the chip to prevent drying and
the offset resistance is set relative to the closed circuit reading
for the settled sample.
[0102] Coagulation Test.
[0103] In accordance with the principles of the present invention,
and as mentioned above, the present techniques and procedures may
be utilized to perform a number of fluid and blood tests. As one
example, the present invention may be used to determine an amount
of time required for a blood sample to coagulate or undergo some
other chemical or physical transformation. When blood is used as
the sample to be analyzed, the transformation of interest is
typically the formation of a blood clot, and the reagent product
information is generally a clot curve. As to the actual procedure,
referring to FIG. 7, after a blood sample is introduced into the
sample retaining area according to, for example, the above
procedures, the sample is mixed with the reagent to commence
formation of a reagent product 710.
[0104] As described above, this mixing includes moving an
air-liquid boundary of the sample through a reagent mixing region
of the sample retaining area until the reagent is at least
substantially dissolved in a vicinity of the air liquid boundary of
the sample. Specifically, the reciprocating movement includes
moving the sample toward the sensing surface of the sensor until
the sensor detects the presence of the sample, followed by moving
the sample away from the sensing surface of the sensor until the
sensor detects the absence of the sample. Thus, upon detecting the
absence of the sample from the sample detection location by the
sensor, the system moves an edge of the sample past an edge of the
sensor into the sample detection location so that at least a
substantial portion of the sample is located therein. Likewise,
upon detecting the presence of the sample in the sample detection
location by the sensor, the system moves the edge of the sample
past the edge of the sensor and out of the sample detection
location so that less than a substantial portion of the sample is
located therein. Additionally, although in this embodiment movement
occurs immediately upon the detection of the presence or the
absence of the sample, in alternate embodiments this movement may
be delayed to occur a predetermined amount of time after
detection.
[0105] In addition, this movement may be used to create a reagent
rich portion in the sample. More specifically, the mixing movement
occurs in a reagent mixing area formed in the sample retaining
area. In this embodiment, the mixing includes repeated
reciprocating movement through the reagent mixing area by only a
first portion of the sample. As a result, movement of a remainder
of the sample occurs in the sample retaining area outside of the
reagent mixing area. In this manner, the first portion has a higher
reagent concentration than that of the remainder.
[0106] Hence, data may be collected by a sensor from only this
first portion of the sample to obtain results that are more
accurate than available from prior art devices.
[0107] By repeating this movement for a predetermined period of
time, for instance long enough to dissolve the reagent, a reagent
rich portion is formed in the sample. Through similar repeated
movements, that is, moving an air-liquid boundary of the sample
over the sensing surface until completion of a sample analysis, an
accumulation of material on or about the sensor may also be
prevented during data collection 720.
[0108] After data collection 720, as will be discussed below, the
procedure continues with a step of extracting reagent product
information, or in this case, clot curve data 730 and then
concludes with the actual calculation of the sample clot time
740.
[0109] In accordance with the principles of the present invention,
data collection by, for example, the amperometric sensor occurs
simultaneously with real-time clot detection and sample position
control. In particular, data collection occurs with each movement
of the sample into the sample detection location (i.e., the area in
the vicinity of the amperometric sensor). These movements continue
until a sufficient predetermined transformation of the sample is
detected. The transformation can be any kind of chemical or
physical change, and in this embodiment is at least the partial
formation of a blood clot in the sample.
[0110] Data collection 720 is now discussed in greater detail with
reference to FIG. 8. Initially, the voltage on the sensor is held
at approximately about -45 to about -55 mV for approximately about
2.5 to about 2.6 seconds 810. The voltage on the sensor is then
held at approximately about 95 to about 105 mV for approximately
about 0.5 to about 0.6 seconds 815. Subsequently, the sensor is
sampled for a predetermined sampling period, for instance about
0.01 to about 0.07 seconds, to collect data on the sample at a
single instance 820. This is used to create a data point which is
then stored within, for example, system memory. By varying an
electrode potential of the sensor between each instance of data
collection, electrochemical contamination of the sensor is
prevented. Furthermore, in an alternate embodiment, prior to an
initial data sampling, the electrode potential of the sensor may be
set to a level that causes electrochemical activity of the sample
to remain at a predetermined minimum. Additionally, a Faradaic
component of the collected data is maximized by imposing a time
delay before collecting data.
[0111] After the collection of each data point, reagent product
information (i.e., clot curve information) is extracted and
analyzed for the real time formation of a blood clot 825. As will
be discussed below with reference to FIG. 9, the formation of a
blood clot is determined by analyzing the data, basically, for a
rise and then a leveling off of the amperometric sensor current
830. If such a condition is not detected, processing resumes with
the sampling procedure described above. However if such a condition
is detected, the transformation time is calculated by utilizing the
extracted reagent product information.
[0112] Occurring simultaneously with the data collection is the
procedure of maintaining the sample position 850. By facilitating
synchronized movement of the sample with data collection, the
effects of motion on the sensor may be eliminated. As to this
synchronized movement, the sample is moved forward when
conductivity measured at the sensor is less than a predetermined
minimum. Likewise, the sample is moved backward when the
conductivity measured at the sensor is greater than a predetermined
maximum. This process is repeated until a sensor data point is
recorded by the sensor 855.
[0113] Upon indication of a sensor data point, the sample is moved
backward to completely cover the sensor surface 860. This movement
continues until an edge of the sample moves past an edge of the
sensor 865. At that time, movement stops thus holding the position
of the sample 870. Subsequently, the sample is moved forward until
the sample edge passes the edge of the sensor 875. From there,
processing returns to the step of maintaining sample position for
the collection of another data point 850.
[0114] The process of extracting reagent product information from
the data to determine a transformation time is now discussed with
reference to FIGS. 9A-9C. In this particular example, the process
basically calculates a transformation time by utilizing time, slope
and amplitude of the clot curve, or in other words, the reagent
product information. Specifically, the process utilizes a curve
rise time, a maximum slope, and a change in current between a
baseline and an upper shoulder, which are defined, respectively, as
a trend line drawn through a portion of an amperometric waveform
occurring before a current rise and as a point occurring when a
slope of a clot curve drops to a predetermined level. Furthermore,
the curve rise time is defined as a time at which a current rises
to a halfway point between the baseline and the upper shoulder.
Even more particularly, the predetermined level defining the
shoulder may be approximately about 40% to about 60% of the maximum
slope.
[0115] Initially, the system accesses data collected in the
procedure discussed above from, for example, system memory 910.
Then, a maximum current is determined 912. Using this information,
a comparison is made between the maximum current and the expected
limits of the current 914. Based on this comparison, an error
result is reported and the analysis is terminated if the maximum
current is not within its expected limits 916. If, however, the
maximum current is within the expected limits, processing continues
with the determination of a minimum current 918.
[0116] Subsequently, a comparison is made between the minimum
current and with the current's expected limits 920. If the minimum
current is not within the expected limits, an error result is
reported and the process is terminated 922. On the other hand, if
the minimum current is within the expected limits, processing
continues with the determination of a baseline, as discussed
below.
[0117] After verifying that the maximum and minimum currents are
within their expected limits, a baseline is determined 924, which
as mentioned above is a trend line drawn through a portion of an
amperometric waveform occurring before a current rise. As one
example, this baseline may be a flat line drawn through the minimum
current. The baseline is then compared with its expected limits
926. Based on this comparison, an error result is reported and the
analysis is terminated if the baseline is not within the expected
limits 928. In contrast, if the baseline is within its expected
limits, processing continues with a comparison between the times of
occurrence of the maximum and minimum currents 930.
[0118] If the maximum current is found earlier in time than the
minimum current, then the absence of clot formation is reported
932. However, if the maximum current is found later in time than
the minimum current, the process continues with the determination
of an amplitude and a time of the maximum slope 934. From there,
both the amplitude and time of maximum slope are compared with
their expected limits 936. If the amplitude and time of maximum
slope are not within the expected limits, an error result is
reported and the process is terminated 938.
[0119] Subsequent to the amplitude and maximum slope checks, the
system of the present invention calculates the time of the
occurrence, if any, of the shoulder, which as discussed above is
the point where a slope of the clot curve decays to 50% of the
maximum clot curve slope. If such an occurrence is identified, the
time of such occurrence as well as the actual current at that time
are recorded in, for instance, system memory 940. According to this
determination, if a shoulder was not found 942, the absence of clot
formation is indicated and the process is terminated 944.
[0120] On the other hand, if a shoulder was detected, a current
change or idelta is determined by subtracting the baseline current
from the shoulder current 946. This idelta, then, is compared with
its expected limits 948. If idelta is not within its expected
limits, idelta is compared with a clot detection limit 950. Then,
if idelta is not within its expected limits and not below the clot
detection limit, an error result is indicated and the instant
process is terminated 952. If idelta is not within the expected
limits but is nevertheless below a clot detection limit, an absence
of a clot formation is reported and the process is terminated
954.
[0121] Returning to the comparison of idelta with its expected
limits 948, if idelta is within its expected limits, a rise time is
determined 956. As mentioned above, this rise time is the time at
which the current rises to a halfway point between the baseline and
the upper shoulder. Next, the rise time is compared with its
expected results 958. If the rise time is not within the expected
limits an error is reported. Otherwise, the rise time is reported
as the clot formation time, and with this final determination, data
extraction in this embodiment ends with all relevant data being
stored to system memory.
[0122] In addition, several other features should be noted. More
particularly, the reagents used in the method of the invention may
be a substrate for an enzyme in a coagulation cascade. In this
case, the reagent product is an electroactive species, and the
material to be prevented from accumulating comprises either
components of the sample adsorbable onto the surface of a sensor
(thus, potentially fouling the sensor) and/or components of a dried
form of the sample. In another embodiment of the invention, a
sensor may have immobilized on it a receptor, which is capable of
binding to a ligand in the sample.
[0123] Although the techniques of the present invention as shown as
being implemented on the systems described above, it is to be
understood that other systems are equally capable of implementing
the above features. For example, even though the above systems are
intended to be useable as hand-held point-of-care devices, it is
alsonceivable that the instant invention may be implemented in a
computing unit such as that depicted in FIG. 10. In this regard,
FIG. 10 is an illustration of a main central processing unit which
is also capable of implementing some or all of the computer
processing in accordance with a computer implemented embodiment of
the present invention. The procedures described herein are
presented in terms of program procedures executed on, for example,
a computer or network of computers.
[0124] Viewed externally in FIG. 10, a computer system designated
by reference numeral 218 has a computer 234 having disk drives 236
and 238. Disk drive indications 236 and 238 are merely symbolic of
a number of disk drives which might be accommodated by the computer
system. Typically, these would include a floppy disk drive 236, a
hard disk drive (not shown externally) and a CD ROM indicated by
slot 238. The number and type of drives vary, typically with
different computer configurations. Disk drives 236 and 238 are in
fact optional, and for space considerations, are easily omitted
from the computer system used in conjunction with the production
process/apparatus described herein.
[0125] The computer system also has an optional display 240 upon
which information is displayed. In some situations, a keyboard 242
and a mouse 244 are provided as input devices to interface with the
central processing unit 234. Then again, for enhanced portability,
the keyboard 242 is either a limited function keyboard or omitted
in its entirety. In addition, mouse 244 optionally is a touch pad
control device, or a track ball device, or even omitted in its
entirety as well. In addition, the computer system also optionally
includes at least one infrared transmitter and/or infrared received
for either transmitting and/or receiving infrared signals, as
described below.
[0126] FIG. 11 illustrates a block diagram of the internal hardware
of the computer system 218 of FIG. 10. A bus 248 serves as the main
information highway interconnecting the other components of the
computer system 218. CPU 250 is the central processing unit of the
system, performing calculations and logic operations required to
execute a program. Read only memory (ROM) 252 and random access
memory (RAM) 254 constitute the main memory of the computer. Disk
controller 256 interfaces one or more disk drives to the system bus
248. These disk drives are, for example, floppy disk drives such as
262, or CD ROM or DVD (digital video disks) drive such as 258, or
internal or external hard drives 260. As indicated previously,
these various disk drives and disk controllers are optional
devices.
[0127] A display interface 264 interfaces display 240 and permits
information from the bus 248 to be displayed on the display 240.
Again as indicated, display 240 is also an optional accessory. For
example, display 240 could be substituted or omitted.
Communications with external devices, for example, the other
components of the system described herein, occur utilizing
communication port 266. For example, optical fibers and/or
electrical cables and/or conductors and/or optical communication
(e.g., infrared, and the like) and/or wireless communication (e.g.,
radio frequency (RF), and the like) can be used as the transport
medium between the external devices and communication port 266.
Peripheral interface 246 interfaces the keyboard 242 and the mouse
244, permitting input data to be transmitted to the bus 248. In
addition to the standard components of the computer, the computer
also optionally includes an infrared transmitter and/or infrared
receiver. Infrared transmitters are optionally utilized when the
computer system is used in conjunction with one or more of the
processing components/stations that transmits/receives data via
infrared signal transmission. Instead of utilizing an infrared
transmitter or infrared receiver, the computer system optionally
uses a low power radio transmitter and/or a low power radio
receiver. The low power radio transmitter transmits the signal for
reception by components of the production process, and receives
signals from the components via the low power radio receiver. The
low power radio transmitter and/or receiver are standard devices in
industry.
[0128] FIGS. 12 is an illustration of an exemplary memory medium
268 which can be used with disk drives illustrated in FIGS. 10 and
11. Typically, memory media such as floppy disks, or a CD ROM, or a
digital video disk will contain, for example, a multi-byte locale
for a single byte language and the program information for
controlling the computer to enable the computer to perform the
functions described herein. Alternatively, ROM 252 and/or RAM 254
illustrated in FIGS. 10 and 11 can also be used to store the
program information that is used to instruct the central processing
unit 250 to perform the operations associated with the production
process.
[0129] Although computer system 218 is illustrated having a single
processor, a single hard disk drive and a single local memory, the
system 218 is optionally suitably equipped with any multitude or
combination of processors or storage devices. Computer system 218
is, in point of fact, able to be replaced by, or combined with, any
suitable processing system operative in accordance with the
principles of the present invention, including sophisticated
calculators, and hand-held, laptop/notebook, mini, mainframe and
super computers, as well as processing system network combinations
of the same.
[0130] Conventional processing system architecture is more fully
discussed in Computer Organization and Architecture, by William
Stallings, MacMillan Publishing Co. (3rd ed. 1993); conventional
processing system network design is more fully discussed in Data
Network Design, by Darren L. Spohn, McGraw-Hill, Inc. (1993), and
conventional data communications are more fully discussed in Data
Communications Principles, by R. D. Gitlin, J. F. Hayes and S. B.
Weinstain, Plenum Press (1992) and in The Irwin Handbook of
Telecommunications, by James Harry Green, Irwin Professional
Publishing (2nd ed. 1992). Each of the foregoing publications is
incorporated herein by reference. Alternatively, the hardware
configuration is, for example, arranged according to the multiple
instruction multiple data (MIMD) multiprocessor format for
additional computing efficiency. The details of this form of
computer architecture are disclosed in greater detail in, for
example, U.S. Pat. No. 5,163,131; Boxer, A., Where Buses Cannot Go,
IEEE Spectrum, February 1995, pp. 41-45; and Barroso, L. A. et al.,
RPM: A Rapid Prototyping Engine for Multiprocessor Systems, IEEE
Computer February 1995, pp. 26-34, all of which are incorporated
herein by reference.
[0131] In alternate preferred embodiments, the above-identified
processor, and, in particular, CPU 250, may be replaced by or
combined with any other suitable processing circuits, including
programmable logic devices, such as PALs (programmable array logic)
and PLAs (programmable logic arrays). DSPs (digital signal
processors), FPGAs (field programmable gate arrays), ASICs
(application specific integrated circuits), VLSIs (very large scale
integrated circuits) or the like.
[0132] The many features and advantages of the invention are
apparent from the detailed specification, and thus, it is intended
by the appended claims to cover all such features and advantages of
the invention which fall within the true spirit and scope of the
invention. Further, since numerous modifications and variations
will readily occur to those skilled in the art, it is not desired
to limit the invention to the exact construction and operation
illustrated and described, and accordingly, all suitable
modifications and equivalents may be resorted to, falling within
the scope of the invention.
* * * * *