SYSTEMS AND METHODS OF DISCRIMINATING BETWEEN A CONTROL SAMPLE AND A TEST FLUID USING CAPACITANCE

• US 20120080323A1
• Filed: 09/30/2010
• Published: 04/05/2012
• Est. Priority Date: 09/30/2010
• Status: Active Grant

• Current Assignee: LifeScan IP Holdings, LLC
• Original Assignee: Cilag Gmbh International (Johnson & Johnson)
• Inventors: Chatelier, Ronald C., Hodges, Alastair M.
• Granted Patent: US 8,617,370 B2
• Time in Patent Office: Days
• US Class Current: 205/775
• CPC Class Codes: C12Q 1/005 involving specific analytes or enzymes including groups of enzymes, e.g. oxydases; C12Q1/004 takes precedence
• CPC Class Codes: G01N 27/28 Electrolytic cell components
• CPC Class Codes: G01N 27/3274 Corrective measures, e.g. error detection, compensation for temperature or hematocrit, calibration coding of calibration information G01N33/48771
• CPC Class Codes: G01N 33/48707 by electrical means G01N33/49, G01N33/493 take precedence

Abstract

Methods for distinguishing between an aqueous non-blood sample (e.g., a control solution) and a blood sample are provided herein. In one aspect, the method includes using a test strip in which multiple current transients are measured by a meter electrically connected to an electrochemical test strip. The current transients are used to determine if a sample is a blood sample or an aqueous non-blood sample based on characteristics of the sample (e.g., amount of interferent present, reaction kinetics, and/or capacitance). The method can also include calculating a discrimination criteria based upon these characteristics. Various aspects of a system for distinguishing between a blood sample and an aqueous non-blood sample are also provided herein.

Claims

1. A method for distinguishing between a blood sample and an aqueous non-blood sample, the method comprising:

(a) applying a first test potential between a first electrode and a second electrode when a sample is introduced into an electrochemical cell and measuring a first current transient;

(b) applying a second test potential between a first electrode and a second electrode, the second test potential being sufficient to oxidize a reduced mediator at the second electrode and measuring a second current transient;

(c) measuring a capacitance of the electrochemical cell;

(d) applying a third test potential between a first electrode and a second electrode, the third test potential being sufficient to oxidize a reduced mediator at the first electrode, and measuring a third current transient;

(e) calculating, based on the first current transient, a first reference value;

(f) calculating, based on the second and third current transients, a second reference value;

(g) calculating, based on at least the measured capacitance, a capacitance index;

(h) calculating, based on the first reference value and the capacitance index, a third reference value; and

(i) determining, based on the second and third reference values, whether the sample is a blood sample or an aqueous non-blood sample.

2. The method of claim 1, wherein the capacitance index is proportional to said measured capacitance of the electrochemical cell.

3. The method of claim 2, wherein the capacitance index is a ratio of an average capacitance of electrochemical cells of the same type and the measured capacitance of the electrochemical cell.

4. The method of claim 1, wherein the first reference value is calculated based upon at least one current value from the first current transient.

5. The method of claim 1, wherein the first reference value is calculated based upon a summation of current values measured during the first current transient.

6. The method of claim 5, wherein the summation is represented by an equation, the equation being

7. The method of claim 1, wherein the second reference value is based on a percent completion of a chemical reaction.

8. The method of claim 1, wherein the second reference value is based upon at least one current value from the second current transient and at least one current value from the third current transient.

9. The method of claim 1, wherein the second reference value is based upon a second current value at about the end of the second current transient and a third current value at about the beginning of the third current transient.

10. The method of claim 9, wherein the second reference value is based upon a ratio of the second current value and the third current value.

11. The method of claim 1, further comprising the step of measuring a concentration of an analyte.

12. The method of claim 11, wherein if the sample is found to be an aqueous non-blood sample the analyte concentration associated with the aqueous non-blood sample is flagged.

13. The method of claim 1, wherein step (i) further comprises using two inequalities to determine if the sample is an aqueous non-blood sample or a blood sample.

14. The method of claim 1, wherein step (i) further comprises:

comparing the second reference value to a pre-determined threshold equation; and

comparing the third reference value to a pre-determined threshold value to determine if the sample is an aqueous non-blood sample or a blood sample.

15. The method of claim 14, wherein the pre-determined threshold equation is a function of the third reference value.

16. The method of claim 1, wherein the aqueous non-blood sample comprises a control sample.

17. A system for distinguishing between a blood sample and an aqueous non-blood sample, the system comprising:

(a) a test strip including electrical contacts for mating with a test meter and an electrochemical cell comprising;

(i) a first electrode and a second electrode in a spaced apart relationship; and

(ii) a reagent; and

(b) a test meter including a processor adapted to receive current data from the test strip, and data storage containing discrimination criteria so that a blood sample can be distinguished from an aqueous non-blood sample based on a first reference value, a second reference value, and a capacitance index.

18. The system of claim 17, wherein the discrimination criteria is derived from a first reference value that is representative of antioxidant concentration and a second reference value that is representative of reaction kinetics.

19. The system of claim 17, wherein the discrimination criteria includes an empirically derived discrimination line.

20. The system of claim 17, wherein the capacitance index comprises a ratio of an average capacitance of electrochemical cells of the same type and a measured capacitance of the electrochemical cell.

21. The system of claim 17, wherein the aqueous non-blood sample is a control solution.

22. A method for calculating a discrimination criteria for programming into a test meter for distinguishing between a blood sample and an aqueous non-blood sample, the method comprising:

(a) calculating a first reference value and a second reference value for a plurality of aqueous non-blood samples,

(b) calculating a third reference value based on the first reference value, the third reference value being proportional to a capacitance index; and

(b) calculating a discrimination criteria based on the second reference value and the third reference value for the plurality of aqueous non-blood samples.

23. The method of claim 22, wherein the first reference value is representative of antioxidant concentration and the second reference value is representative of reaction kinetics.

24. The method of claim 22, wherein the capacitance index comprises a ratio of an average capacitance of electrochemical cells of the same type and the measured capacitance of the electrochemical cell when a sample is introduced.

25. The method of claim 22, wherein the plurality of aqueous non-blood samples comprise a plurality of control solutions.

26. A method for distinguishing between a blood sample and an aqueous non-blood sample, the method comprising:

(a) introducing a sample into an electrochemical cell, the electrochemical cell comprising;

(i) two electrodes in a spaced apart relationship; and

(ii) a reagent;

(b) applying a first test potential, having a first polarity, between the electrodes, and measuring cell current;

(c) measuring a capacitance of the electrochemical cell;

(d) summing at least two current values measured during the first test potential to generate a first reference value;

(e) calculating a capacitance index related to the measured capacitance;

(f) using the capacitance index and the first reference value to distinguish between a blood sample and an aqueous non-blood sample.

27. The method of claim 26, further comprising calculating a second reference value related to reaction kinetics;

and using the capacitance index, the first reference value, and the second reference value to distinguish between a blood sample and an aqueous non-blood sample.

28. The method of claim 26, wherein the aqueous non-blood sample comprises a control solution.

29. The method of claim 26, wherein the capacitance index comprises a ratio of an average capacitance of electrochemical cells of the same type and the measured capacitance of the electrochemical cell.