SYSTEM AND METHOD FOR MEASURING AN ANALYTE IN A SAMPLE

• US 20130068633A1
• Filed: 09/14/2012
• Published: 03/21/2013
• Est. Priority Date: 01/17/2008
• Status: Active Grant

• Current Assignee: Cilag Gmbh International (Johnson & Johnson)
• Original Assignee: Lifescan Incorporated (Duv Holding Corporation)
• Inventors: Chatelier, Ronald C., Hodges, Alastair M., Nandagopalan, Santhanagopalan
• Granted Patent: US 8,916,040 B2
• Time in Patent Office: Days
• US Class Current: 205/791.5
• CPC Class Codes: C12Q 1/006 for glucose
• 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 27/4163 checking the operation of, or calibrating, the measuring apparatus G01N27/3274, G01N27/4175 and G01N33/0006 take precedence

Abstract

Methods of determining a corrected analyte concentration in view of some error source are provided herein. The methods can be utilized for the determination of various analytes and/or various sources of error. In one example, the method can be configured to determine a corrected glucose concentration in view of an extreme level of hematocrit found within the sample. In other embodiments, methods are provided for identifying various system errors and/or defects. For example, such errors can include partial-fill or double-fill situations, high track resistance, and/or sample leakage. Systems are also provided for determining a corrected analyte concentration and/or detecting some system error.

Claims

1. A method of identifying a defect in a test strip, comprising:

applying a first test voltage V₁ for a first test time interval T₁ between a first electrode and a second electrode sufficient to oxidize a reduced mediator at the second electrode;

applying a second test voltage V₂ for a second test time interval T₂ between a first electrode and a second electrode sufficient to oxidize a reduced mediator at the first electrode;

measuring a first test current i₁ and a second test current i₂ that occur during the second test time interval T₂, the second test current i₂ occurring after the first test current i₁; and

determining whether the test strip has the defect using an equation based on the first test current i₁ and the second test current i₂.

2. The method of claim 1, wherein the second test voltage V₂ is applied immediately after the first test voltage V₁.

3. The method of claim 1, wherein the equation comprises a ratio between the first test current i₁ and the second test current i₂.

4. The method of claim 3, wherein the equation comprises a ratio between the first test current i₁ and the difference between the first test current i₁ and the second test current i₂.

5. The method of claim 1, wherein the first test current i₁ is determined at about a beginning of the second time interval T₂.

6. The method of claim 1, wherein the first test current i₁ is a maximum current value occurring during the second time interval T₂.

7. The method of claim 1, wherein the second test current i₂ is determined at about an end of the second time interval T₂.

8. The method of claim 1, wherein the second test current i₂ is a minimum current value occurring during the second time interval T₂.

9. The method of claim 8, further comprising a step of providing an error message indicating a defective test strip if the ratio is greater than a first predetermined threshold.

11. The method of claim 1, wherein the equation is a

12. The method of claim 1, wherein the first test voltage ranges from about zero to about −

600 mV with respect to the second electrode.

13. The method of claim 1, wherein the second test voltage ranges from about 10 mV to about 600 mV with respect to the second electrode.

14. The method of claim 1, wherein the defect is a high track resistance R.

15. The method of claim 14, wherein the high track resistance R is between a connection point on a meter and either the first or second electrode of the test strip.

16. A method of identifying a defect in a test strip comprising:

applying a first test voltage V₁ for a first test time interval T₁ between a first electrode and a second electrode sufficient to oxidize a reduced mediator at the second electrode;

applying a second test voltage V₂ for a second test time interval between a first electrode and a second electrode sufficient to oxidize a reduced mediator at the first electrode;

measuring a first test current i₁, a second test current i₂, a third test current i₃, and a fourth test current i₄ that occur during the second test time interval T₂;

calculating a first logarithm of a first ratio based on the first test current i₁ and the second test current i₂;

calculating a second logarithm of a second ratio based on the third test current i₃ and the fourth test current i₄; and

determining whether the test strip has a defect using an equation based on the first logarithm and the second logarithm.

17. The method of claim 16, wherein the defect is a leakage of fluid between a spacer and the first electrode.

18. The method of claim 16, wherein a reagent layer is disposed on the first electrode so that a portion of the reagent layer is between the spacer and the first electrode.

19. The method of claim 16, wherein the equation is a third ratio represented by

20. The method of claim 16, further comprising a step of providing an error message indicating a defective test strip if the third ratio is less than a predetermined threshold.

21. The method of claim 16, wherein the predetermined threshold is about 1.

22. The method of claim 20, wherein the predetermined threshold is about 0.95.

23. The method of claim 16, wherein the first test current i₁ and the second test current i₂ comprise the two largest current values during the second time interval T₂.

24. The method of claim 16, wherein the fourth test current i₄ is a smallest current value occurring the second time interval T₂.

25. The method of claim 16, wherein a difference between a fourth test current time and a third test current time is greater than a difference between a second test current time and a first test current time.

26. A method of identifying an error in performing a test with a test strip, comprising:

applying a first test voltage V₁ for a first test time interval T₁ between a first electrode and a second electrode;

measuring consecutively a first test current i₁, a second test current i₂, and a third test current i₃; and

determining whether an error was performed by using an equation based on the second test current i₂ and a summation of the absolute value of the first test current i₁ and the absolute value of the third test current i₃.

10. The method of claim 29, wherein the first predetermined threshold is about 1.2.

27. The method of claim 26, wherein a time difference between the measurements of the first test current i₁ and the second test current i₂ ranges from about one nanosecond to about 100 milliseconds.

28. The method of claim 26, wherein a time difference between the measurements of the first test current i₁ and the third test current i₃ ranges from about one nanosecond to about 100 milliseconds.

29. The method of claim 26, wherein the equation is Y=2*abs(i(t))−

abs(i(t−

x))−

abs(i(t+x)), where i(t) is the second test current, i(t−

x) is the first test current, i(t+x) is the third test current, t is a time, and x is an increment of time, and abs represents an absolute function.

30. The method of claim 26, wherein the equation is Z=abs(i(t+x))−

abs(i(t)), where i(t) is the second test current, i(t+x) is the third test current, t is a time, and x is an increment of time, and abs represents an absolute function.