System, method and computer implemented process for assaying coagulation in fluid samples

• US 20020177958A1
• Filed: 07/08/2002
• Published: 11/28/2002
• Est. Priority Date: 02/10/2000
• Status: Abandoned Application

• Current Assignee: i STAT Corporation (Abbott Laboratories Incorporated)
• Original Assignee: i STAT Corporation (Abbott Laboratories Incorporated)
• Inventors: Opalsky, David, Maczuszenko, Andy, Widrig Opalsky, Cindra A., Lauks, Imants R.
• Application Number:
  US10/189,729
• Publication Number:
  US 20020177958A1
• Time in Patent Office: Days
• US Class Current: 702/25
• CPC Class Codes: B01L 2200/0605 Metering of fluids
• CPC Class Codes: B01L 2200/0673 Handling of plugs of fluid surrounded by immiscible fluid
• CPC Class Codes: B01L 2200/14 Process control and prevention of errors
• CPC Class Codes: B01L 2200/143 Quality control, feedback systems
• CPC Class Codes: B01L 2300/0645 Electrodes
• CPC Class Codes: B01L 2300/0816 Cards, e.g. flat sample carriers usually with flow in two horizontal directions
• CPC Class Codes: B01L 2300/0867 Multiple inlets and one sample wells, e.g. mixing, dilution
• CPC Class Codes: B01L 2300/087 Multiple sequential chambers
• CPC Class Codes: B01L 2400/0406 capillary forces
• CPC Class Codes: B01L 2400/0415 electrical forces, e.g. electrokinetic
• CPC Class Codes: B01L 2400/0439 ultrasonic vibrations, vibrating piezo elements
• CPC Class Codes: B01L 2400/0478 pistons
• CPC Class Codes: B01L 2400/0481 squeezing of channels or chambers
• CPC Class Codes: B01L 2400/0487 fluid pressure, pneumatics
• CPC Class Codes: B01L 2400/0688 surface tension valves, capillary stop, capillary break
• CPC Class Codes: B01L 3/5027 by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip B01L3/5023 takes precedence; micromixers B01F33/30; microreactors for synthesis B01J19/0093; microcapillary devices in general B81B1/00
• CPC Class Codes: B01L 3/502746 characterised by the means for controlling flow resistance, e.g. flow controllers, baffles B01L3/502738 takes precedence
• CPC Class Codes: G01N 11/04 through a restricted passage, e.g. tube, aperture
• CPC Class Codes: G01N 33/4905 Determining clotting time of blood by chemical methods G01N33/86, C12Q1/54

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.

Claims

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.