Temperature-adjusted analyte determination for biosensor system

• US 8,148,162 B2
• Filed: 07/20/2010
• Issued: 04/03/2012
• Est. Priority Date: 02/27/2006
• Status: Active Grant

• Current Assignee: Ascensia Diabetes Care Holdings AG (PHC Holdings Corporation)
• Original Assignee: Bayer Healthcare LLC (Bayer AG)
• Inventors: Wu, Huan-Ping, Nelson, Christine D.
• Primary Examiner(s): Wallenhorst, Maureen
• Application Number:
  US12/839,643
• Publication Number:
  US 20110039286A1
• Time in Patent Office: 623 Days
• Field of Search: 436/8, 436/14, 436/63, 436/95, 436/147, 436/149, 436/150, 436/164, 422/55, 422/68.1, 422/82.01, 422/82.02, 422/82.05, 422/82.09, 422/82.12, 422/400, 73/10.1, 73/10.2, 435/14, 708/205
• US Class Current: 436/147
• CPC Class Codes: A61B 2560/0252 using ambient temperature
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1486 using enzyme electrodes, e.g. with immobilised oxidase
• CPC Class Codes: G01N 27/26 by investigating electrochemical variables; by using electrolysis or electrophoresis
• 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: G16B 40/10 Signal processing, e.g. from mass spectrometry [MS] or from PCR
• CPC Class Codes: G16B 99/00 Subject matter not provided for in other groups of this subclass
• CPC Class Codes: Y10T 436/10 Composition for standardization, calibration, simulation, stabilization, preparation or preservation; processes of use in preparation for chemical testing
• CPC Class Codes: Y10T 436/104998 Glucose, ketone, nitrate standard or control
• CPC Class Codes: Y10T 436/12 Condition responsive control
• CPC Class Codes: Y10T 436/144444 Glucose

Abstract

A biosensor system determines analyte concentration from an output signal generated by an oxidation/reduction reaction of the analyte. The biosensor system adjusts a correlation for determining analyte concentrations from output signals at one temperature to determining analyte concentrations from output signals at other temperatures. The temperature-adjusted correlation between analyte concentrations and output signals at a reference temperature may be used to determine analyte concentrations from output signals at a sample temperature.

Claims

1. A method for determining an analyte concentration in a sample of a biological fluid, comprising:

determining a sample temperature of the sample;

generating an output signal in response to a redox reaction of an analyte in the sample;

selecting a slope value and an intercept value from a correlation of output signals and analyte concentrations previously determined at a reference temperature;

adjusting the selected slope value and the selected intercept value in response to the sample temperature to provide an adjusted slope value and an adjusted intercept value; and

calculating an analyte concentration from the output signal and the adjusted slope and intercept values.

2. The method of claim 1, where the slope adjustment is represented as follows:

S_T=S*(a₂*T₁²+a₁*T₁+a₀),

where S_T is the adjusted slope value, S is the selected slope value, a₀, a₁, and a₂ are slope temperature function coefficients, and T₁ is the sample temperature.

3. The method of claim 2, where a₀ is 0.6703, a₁ is 0.01453and a₂ is −

5.765×

10<sup>−

5</sup>.

4. The method of claim 1, where the intercept adjustment is represented as follows:

Int_T=Int*(b₂*T₁²+b₁*T₁+b₀),

where Int_T is the adjusted intercept value, Int is the selected intercept value, b₀, b₁, and b₂ are intercept temperature function coefficients, and T₁ is the sample temperature.

5. The method of claim 4, where b₀ is 1.284, b₁ is −

0.01389 and b₂ is 1.023.

6. The method of claim 1, where the analyte concentration calculation is represented as follows:

7. The method of claim 1, where sample temperature is determined by measuring the sample temperature, by calculating the sample temperature from the output signal, or by measuring an ambient temperature and assuming the sample temperature to be the same or similar to the ambient temperature.

8. The method of claim 1, where the sample temperature is determined by measuring the sample temperature using a thermister or a thermometer.

9. The method of claim 1, further comprising comparing the sample temperature with a too high temperature and a too low temperature prior to generating an output signal;

where when the sample temperature is greater than the too high temperature the method is stopped and a “

temperature too high”

error mode is set,

when the sample temperature is less than the too low temperature the method is stopped and a “

temperature too low”

error mode is set, and

when the sample temperature is within the range of the too high temperature and the too low temperature, no error mode is set and the method is allowed to proceed to generate an output signal.

10. The method of claim 9, where the too high temperature is 50°

C. and the too low temperature is 5°

C.

11. The method of claim 1, where the output signal is generated using an optical sensor system comprising a chemical indicator.

12. The method of claim 11, where the output signal is an attenuated incident beam or is light produced by the chemical indicator.

13. The method of claim 1, where the output signal is generated using an electrochemical sensor system comprising a mediator.

14. The method of claim 13, where the electrochemical sensor system uses amperometry, gated amperometry, coulometry, voltammetry, or gated voltammetry.

15. The method of claim 1, further comprising generating the output signal in response to pulsed input signals.

16. The method of claim 1, where the slope value and the intercept value are selected from a program number assignment (PNA) table.

17. The method of claim 1, where the reference temperature is 10°

C., 20°

C., 25°

C., 30°

C., or 40°

C.

18. The method of claim 1, where the slope adjustment is represented as follows:

S_T=S*(a₂*T₁²+a₁*T₁+a₀),

where S_T is the adjusted slope value, S is the selected slope value, a₀, a₁, and a₂ are slope temperature function coefficients, and T₁ is the sample temperature; and

where the intercept adjustment is represented as follows;

Int_T=Int*(b₂*T₁²+b₁*T₁+b₀),

where Int_T is the adjusted intercept value, Int is the selected intercept value, b₀, b₁, and b₂ are intercept temperature function coefficients, and T₁ is the sample temperature.

19. The method of claim 18, where the method is carried out using a sensor system comprising a sensor strip, and the slope temperature function coefficients and the intercept temperature coefficients are selected based on the sensor strip.

20. The method of claim 18, where

a₀ is 0.6703, a₁ is 0.01453 and a₂ is −

5.765×

10<sup>−

5</sup>, and

b₀ is 1.284, b₁ is −

0.01389 and b₂ is 1.023.

21. The method of claim 1, where the reference temperature is 25°

C., and the analvte concentration calculation is represented as follows;

22. The method of claim 21, where the method is carried out using a sensor system comprising a sensor strip, and the slope temperature function coefficients and the intercept temperature coefficients are selected based on the sensor strip.

23. The method of claim 21, where

a₀ is 0.6703, a₁ is 0.01453 and a₂ is −

5.765×

10<sup>−

5</sup>, and

b₀ is 1.284, b₁ is −

0.01389 and b₂ is 1.023.

24. The method of claim 1, further comprising comparing the calculated analyte concentration with a maximum allowable analyte concentration;

where when the calculated analyte concentration is greater than the maximum allowable analyte concentration the method is stopped and a “

glucose too high”

error mode is set, and

when the calculated analyte concentration is less than the maximum allowable analyte concentration the calculated analyte concentration is displayed or stored.

25. The method of claim 24, where the maximum allowable analyte concentration is 1500 mg/dL.

26. The method of claim 1, further comprising displaying the calculated analyte concentration.

27. The method of claim 1, further comprising storing the calculated analyte concentration.

28. The method of claim 1, where the analyte comprises glucose and the biological fluid comprises whole blood.