Methods for performing hematocrit adjustment in glucose assays and devices for same

• US 7,972,861 B2
• Filed: 05/13/2005
• Issued: 07/05/2011
• Est. Priority Date: 05/14/2004
• Status: Active Grant

• Current Assignee: Ascensia Diabetes Care Holdings AG (PHC Holdings Corporation)
• Original Assignee: Bayer Healthcare LLC (Bayer AG)
• Inventors: Deng, Yingping, Jamison, Sherry J.
• Primary Examiner(s): WALLENHORST, MAUREEN
• Application Number:
  US11/596,401
• Publication Number:
  US 20070231914A1
• Time in Patent Office: 2,244 Days
• Field of Search: 436/63, 436/69, 436/70, 436/95, 436/149, 436/150, 422/68.1, 422/73, 422/82.01, 422/82.02, 435/14, 435/287.1, 600/347, 600/365, 702/19
• US Class Current: 436/95
• 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: Y10T 436/144444 Glucose

Abstract

Methods and devices for performing in situ hematocrit adjustments during glucose testing using glucose-monitoring products and using those adjusted values to estimate the hematocrit value of blood samples to reduce or eliminate the assay bias caused by the different hematocrit levels of blood samples. One method involves measuring the glucose value, Glu_m, of the blood sample; measuring the resistance of the blood sample (R_cell) using a biosensor reagent; measuring the resistance of plasma (R_plasma) using the biosensor reagent; determining the calculated resistance of red blood cells, R_RBC, of the blood sample according to the relationship
R_RBC=R_cell−R_plasma;
calculating the percent hematocrit, % Hct_c, of the blood sample; determining whether to adjust the glucose value, Glu_m, to an adjusted glucose value, Glu_adj; and using the percent hematocrit, % Hct_c, and either the glucose value, Glu_m, or the adjusted glucose value, Glu_adj, to adjust for any bias of the biosensor reagent.

Claims

1. A method for adjusting glucose bias, if any, of a blood sample in a glucose-monitoring product comprising the acts of:

(a) measuring the glucose value, Glu_m, of the blood sample;

(b) measuring the resistance of the blood sample, R_cell, using a biosensor reagent;

(c) identifying the resistance of plasma, R_plasma, for a reagent lot of the biosensor reagent during manufacturing;

(d) determining the calculated resistance of red blood cells, R_RBC, of the blood sample according to the relationship;

R_RBC=R_cell−

R_plasma;

(e) calculating the percent hematocrit, % Hct_c, of the blood sample using the calculated resistance of red blood cells R_RBC;

(f) determining whether to adjust the glucose value, Glu_m, to an adjusted glucose value, Glu_adj using the percent hematocrit, % Hct_c; and

(g) using the percent hematocrit, % Hct_c, and the glucose value, Glu_m, or the adjusted glucose value, Glu_adj, from either act (a) or act (f) to adjust for the glucose bias of the blood sample, if any.

2. The method of claim 1, wherein the act of measuring the glucose value, Glu_m, of the blood sample involves using a laboratory glucose analyzer.

3. The method of claim 1, wherein the values of R_RBC and % Hct_c are manually calculated.

4. The method of claim 1, wherein the values of R_RBC and % Hct_c are determined by software used with the glucose-monitoring product.

5. The method of claim 1, wherein the act of measuring R_cell involves measuring the cell resistance of the blood sample between a reference electrode and a working electrode in the biosensor reagent.

6. The method of claim 1, wherein the value of R_plasma is electronically programmed into software used with the glucose-monitoring product.

7. The method of claim 1, wherein the value of R_plasma is included on a calibration chip provided with the biosensor reagent.

8. The method of claim 1, wherein the value of R_plasma is included on a label located on the biosensor reagent.

9. The method of claim 1, wherein the R_plasma involves inputting a predetermined value by a user into the glucose-monitoring product.

10. The method of claim 1, wherein the value of R_RBC is calculated by software used with the glucose-monitoring product.

11. The method of claim 1, wherein the value of R_RBC is calculated manually and input into the glucose-monitoring product.

12. The method of claim 1, wherein the value of % Hct_c is calculated by software used with the glucose-monitoring product.

13. The method of claim 1, wherein the value of % Hct_c is calculated manually and input into the glucose-monitoring product.

14. The method of claim 1, wherein the blood sample is a whole blood sample.

15. A method for adjusting glucose bias, if any, of a blood sample in a glucose-monitoring product, the method comprising the acts of:

measuring the glucose value, Glu_m, of the blood sample;

measuring the cell resistance, R_cell, of the blood sample using a biosensor reagent;

measuring the plasma resistance, R_plasma, of the biosensor reagent;

determining the calculated resistance of red blood cells, R_RBC, of the blood sample according to the relationship;

R_RBC=R_cell−

R_plasma;

calculating the percent hematocrit, % Hct_c, of the blood sample according to the relationship;

% Hct_c=−

k₁*(R_RBC)²+k₂*R_RBC+k₃

where k₁ ranges from about +100 to about −

100, k₂ ranges from about +100 to about −

100, and k₃ ranges from about +100 to about −

100;

determining whether to adjust the glucose value, Glu_m, using the percent hematocrit, % Hct_c ; and

adjusting, if necessary, the glucose value, Glu_m, using the percent hematocrit, % Hct_c, to obtain the adjusted glucose value Glu_adj according to the relationship;

Glu_adj=Glu_m+k₅,

wherein k₅ is an adjustment factor so as to adjust the glucose bias, if any, of the blood sample.

16. The method of claim 15, wherein the act of measuring the glucose value, Glu_m, of the blood sample involves using a laboratory glucose analyzer.

17. The method of claim 15, wherein the values of R_RBC and % Hct_c are manually calculated.

18. The method of claim 15, wherein the values of R_RBC and % Hct_c are determined by software used with the glucose-monitoring product.

19. The method of claim 15, wherein the act of measuring R_cell involves measuring the cell resistance of the blood sample between a reference electrode and a working electrode in the biosensor reagent.

20. The method of claim 15, wherein the value of R_plasma is electronically programmed into software used with the glucose-monitoring product.

21. The method of claim 15, wherein the value of R_plasma is included on a calibration chip provided with the biosensor reagent.

22. The method of claim 15, wherein the value of R_plasma is included on a label located on the biosensor reagent.

23. The method of claim 15, wherein the act of measuring R_plasma involves inputting a predetermined value by a user into the glucose-monitoring product.

24. The method of claim 15, wherein the value of R_RBC is calculated by software used with the glucose-monitoring product.

25. The method of claim 15, wherein the value of R_RBC is calculated manually and input into the glucose-monitoring product.

26. The method of claim 15, wherein the value of % Hct_c is calculated by software used with the glucose-monitoring product.

27. The method of claim 15, wherein the value of % Hct_c is calculated manually and input into the glucose-monitoring product.

28. The method of claim 15, wherein the blood sample is a whole blood sample.