SYSTEMS AND METHODS OF DISCRIMINATING CONTROL SOLUTION FROM A PHYSIOLOGICAL SAMPLE

• US 20090084687A1
• Filed: 09/16/2008
• Published: 04/02/2009
• Est. Priority Date: 09/28/2007
• Status: Active Grant

• Current Assignee: Cilag Gmbh International (Johnson & Johnson)
• Original Assignee: Lifescan Incorporated (Duv Holding Corporation)
• Inventors: Chatelier, Ronald C., Hodges, Alastair M.
• Granted Patent: US 8,778,168 B2
• Time in Patent Office: Days
• US Class Current: 205/792
• CPC Class Codes: C12Q 1/001 Enzyme electrodes
• 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 33/5438 Electrodes
• CPC Class Codes: G01N 33/96 involving blood or serum control standard

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 at least two characteristics (e.g., amount of interferent present and reaction kinetics). The method can also include calculating a discrimination criteria based upon at least two 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) 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;

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

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

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

2. The method of claim 1, wherein the first reference value is proportional to a concentration of an interferent in the sample.

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

4. 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.

5. The method of claim 4, wherein the summation is represented by an equation, the equation being

$i_{\mathrm{sum}}=\sum _{}^{}$

t = 0.05 1 

i 

( t ) ,

where isum is the summation of current values and t is a time.

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

7. 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.

8. 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.

9. The method of claim 8, wherein the second reference value is based upon a ratio of the second current value and the third current value.

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

11. The method of claim 10, 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.

12. The method of claim 1, wherein step (f) further comprises using statistical classification to determine if the sample is an aqueous non-blood sample or a blood sample.

13. The method of claim 1, wherein step (f) further comprises:

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

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

14. The method of claim 13, wherein the pre-determined threshold equation is a function of the first reference value.

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

16. 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 for distinguishing a blood sample from an aqueous non-blood sample based on antioxidant concentration and reaction kinetics.

17. The system of claim 16, wherein the discrimination criteria is derived from an interferent index that is representative of antioxidant concentration and a residual reaction index that is representative of reaction kinetics.

18. The system of claim 16, wherein the discrimination criteria includes an empirically derived discrimination line.

19. The system of claim 16, wherein the aqueous non-blood sample is a control solution.

20. 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 an interferent index and a residual reaction index for a plurality of aqueous non-blood samples; and

(b) calculating a discrimination criteria based on a regression of the interferent index and the residual reaction index for the plurality of aqueous non-blood samples.

21. The method of claim 20, wherein the method further comprises the step of:

plotting an interferent index and a residual reaction index for a plurality of blood samples and shifting the discrimination line towards the plurality of blood samples.

22. The method of claim 20, wherein the plurality of aqueous non-blood samples are a plurality of control solutions.

23. 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) summing at least two current values measured during the first test potential to generate an interferent index; and

(d) using the interferent index to distinguish between a blood sample and an aqueous non-blood sample.

24. The method of claim 23, wherein the aqueous non-blood sample is a control solution.