Method for determining analyte concentration based on slope-based compensation

• US 10,739,350 B2
• Filed: 12/08/2008
• Issued: 08/11/2020
• Est. Priority Date: 12/10/2007
• Status: Active Grant

• Current Assignee: Ascensia Diabetes Care Holdings AG (PHC Holdings Corporation)
• Original Assignee: Ascensia Diabetes Care Holdings AG (PHC Holdings Corporation)
• Inventors: Wu, Huan-Ping
• Primary Examiner(s): Whaley, Pablo S
• Application Number:
  US12/329,698
• Publication Number:
  US 20090177406A1
• Time in Patent Office: 4,264 Days
• Field of Search: None
• CPC Class Codes: G01N 27/3273 Devices therefor, e.g. test element readers, circuitry details not specific to biochemical electrodes G01N33/4875
• CPC Class Codes: G01N 33/66 involving blood sugars, e.g. galactose

Abstract

A biosensor system determines analyte concentration from an output signal generated from a light-identifiable species or a redox reaction of the analyte. The biosensor system adjusts a correlation for determining analyte concentrations from output signals with one or more index functions extracted from the output signals. The index functions determine at least one slope deviation value, ΔS, or normalized slope deviation from one or more error parameters. The slope-adjusted correlation between analyte concentrations and output signals may be used to determine analyte concentrations having improved accuracy and/or precision from output signals including components attributable to bias.

Claims

1. A method for determining an analyte concentration in a fluid sample via a biosensor system, comprising:

providing an analyte measurement device and a sensor strip, the analyte measurement device including a storage device, a sensor interface, and a processor, the processor coupled to storage device and the sensor interface, the sensor interface for receiving the sensor strip, the sensor strip including an electrode that contacts the sensor interface of the measurement device when the sensor strip is placed in the sensor interface;

applying an electrical input signal to the sample via the electrode of the sensor strip when the sensor strip is placed in the sensor interface of the analyte measurement device and a fluid sample is applied to the sensor strip;

generating at least one output signal value from an analysis of the fluid sample via the sensor interface of the analyte measurement device, the at least one output signal value responsive to the analyte concentration in the sample;

determining at least one Δ

S value from at least one error parameter via the processor of the analyte measurement device, where the at least one Δ

S value is a value of slope deviation or a value of normalized slope deviation in relation to at least one previously determined reference correlation relating previously determined reference output signal values to reference sample analyte concentration values, the previously determined reference sample analyte concentration values obtained from a reference instrument, the previously determined reference correlation stored in the storage device of the analyte measurement device, and where the at least one error parameter causes one or more errors in the at least one output signal value; and

determining the analyte concentration in the sample from the at least one output signal value, the at least one Δ

S value, and the at least one previously determined reference correlation relating the at least one output signal value to one of the reference sample analyte concentration values via the processor of the analyte measurement device,

where the determining the analyte concentration in the sample comprises adjusting the at least one previously determined reference correlation with the at least one Δ

S value, and

where the determining the at least one Δ

S value from at least one error parameter and the determining the analyte concentration in the sample from the at least one output signal value are performed by the processor of the analyte measurement device using computer readable software code.

2. The method of claim 1, where the fluid sample is a biological fluid.

3. The method of claim 1, where the analyte comprises glucose and the sample comprises whole blood.

4. The method of claim 1, where a percent bias of an absolute bias value over the reference value in the determined analyte concentration is at most ±

10%.

5. The method of claim 1, where over 95% of the analyte concentrations determined from the method fall within a ±

20% bias limit.

6. The method of claim 1, where the determining of the at least one Δ

S value from the at least one error parameter includes determining the at least one Δ

S value from at least one predetermined index function, the predetermined index function being determined by a regression equation of a plot between the deviation in a slope of the reference correlation in response to the at least one error parameter and, where the at least one predetermined index function is responsive to the at least one error parameter and provides the at least one Δ

S value as a value of slope deviation or a value of normalized slope deviation in relation to the at least one previously determined reference correlation.

7. The method of claim 6, where the at least one error parameter is responsive to error contributors causing an alteration of the at least one output signal value.

8. The method of claim 6, where the at least one error parameter is selected from the group consisting of temperature and hematocrit level.

9. The method of claim 6, where when the at least one error parameter includes multiple error parameters, the multiple error parameters are independently responsive to different error contributors.

10. The method of claim 6, where the at least one error parameter has a correlation with a Δ

S_cal value, the Δ

S_cal value representing the difference between the reference correlation and a hypothetical perfect correlation having an R² value of at least 0.3.

11. The method of claim 6, where the at least one index function transforms the at least one error parameter into the at least one Δ

S value.

12. The method of claim 1, where the input signal comprises pulsed electrical excitations.

13. The method of claim 1, where the output signal value is generated from light.

14. The method of claim 1, where the determining is represented as follows:

15. The method of claim 1, where the at least one previously determined reference correlation and the at least one output signal value are modified with a second Δ

S value, each Δ

S value determined from a different predetermined index function, where the at least one index function is responsive to the at least one error parameter and provides a value of slope deviation or a value of normalized slope deviation in relation to the at least one previously determined reference correlation.

16. The method of claim 15, where different error parameters are transformed by the different index functions to provide the at least two Δ

S values.

17. The method of claim 16, where a correlation between analyte concentration and the different error parameters is represented as follows:

18. The method of claim 17, where Δ

S₁ represents the error parameter responsive to an error contributor providing the largest bias in the determined analyte concentration.

19. The method of claim 14, further comprising determining the remaining system error values, Δ

S_2cal is represented as follows;

20. The method of claim 1, where the determining is with an equation relating percent bias to current.

21. The method of claim 1, where the sample is selected from the group consisting of a biological fluid, a derivative of a biological fluid, and combinations thereof.

22. The method of claim 1, where the measurement device is a portable measurement device.

23. The method of claim 1, further comprising normalizing the at least one Δ

S value.

24. The method of claim 23, further comprising normalizing the at least one Δ

S value in response to a slope of the at least one previously determined reference correlation.

25. The method of claim 23, further comprising normalizing the at least one Δ

S value in response to a normalized slope function.

26. The method of claim 6, where the at least one predetermined index function is predetermined from normalized slope deviations with a calibration slope of the at least one previously determined reference correlation.

27. The method of claim 6, further comprising generating at least two output signal values from the sample,

where the at least two output signal values are responsive to the analyte concentration of the sample,

where the at least one predetermined index function represents a correlation between %-bias of the analyte concentration of the sample and a ratio of the at least two output signal values.