USE OF MULTIPLE DATA POINTS AND FILTERING IN AN ANALYTE SENSOR

• US 20060281985A1
• Filed: 06/01/2006
• Published: 12/14/2006
• Est. Priority Date: 06/02/2005
• Status: Active Grant

• Current Assignee: Konamite Limited
• Original Assignee: Isense Corporation
• Inventors: Ward, W. Kenneth, Jacobs, Peter G.
• Granted Patent: US 7,976,466 B2
• Time in Patent Office: Days
• US Class Current: 600/365
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 5/1486 using enzyme electrodes, e.g. with immobilised oxidase

Abstract

Embodiments of the present invention improve the accuracy of measurements and/or in vivo calibrations of a biosensor by (1) using more than one sensor signal value and/or more than one directly sampled and measured value, such as a capillary blood glucose value, and/or by (2) delaying the acquisition of a sensor output value that is compared with a directly sampled and measured value, such as a capillary blood glucose value, during a calibration. In an embodiment of the present invention, the median of a series of measured values, or a median or mean of the medians, may be utilized to provide more consistent and accurate measurement data and/or to compensate for error or artifact.

Claims

1. A method of calibrating a biosensor that measures an analyte, comprising:

obtaining a blood analyte concentration;

obtaining a plurality of biosensor output signal values;

applying a median filter to said plurality of biosensor output signal values to obtain a median sensor output value;

comparing said blood analyte concentration with said median sensor output value to obtain a sensor sensitivity value; and

utilizing said sensor sensitivity value to calibrate the signal output of said biosensor.

2. The method of claim 1, wherein at least one of said plurality of biosensor output signal values is obtained between 4 and 10 minutes after obtaining said blood analyte concentration.

3. The method of claim 1, wherein at least one of said plurality of biosensor output signal values is obtained about 5 minutes after obtaining said blood analyte concentration.

4. The method of claim 1, wherein said obtaining a blood analyte concentration comprises obtaining a blood sample via a fingerstick and using an external analyte meter to measure the blood analyte concentration of the blood sample.

5. The method of claim 1, wherein said plurality of biosensor output signal values are obtained during an interval of 1 minute.

6. The method of claim 1, wherein said plurality of biosensor output signal values are obtained during a plurality of intervals.

7. The method of claim 6, wherein said median filter first obtains a median interval sensor output value for each of said plurality of intervals, and then said median filter obtains a median sensor output value from said median interval sensor output values.

8. The method of claim 6, further comprising a mean filter that first obtains a mean interval sensor output value for each of said plurality of intervals, and then said median filter obtains a median sensor output value from said mean interval sensor output values.

9. The method of claim 1, wherein obtaining a blood analyte concentration comprises obtaining a plurality of blood analyte concentrations.

10. The method of claim 9, further comprising obtaining a sensor sensitivity value for each blood analyte concentration obtained, and wherein said sensor sensitivity values are temporally weighted.

11. The method of claim 1, wherein said signal output is displayed as a value on an electronic monitoring unit.

12. The method of claim 1, further comprising obtaining a value for a background current for said biosensor and subtracting said background current value from said plurality of biosensor output signal values or from said median sensor output value prior to obtaining said sensor sensitivity value.

13. The method of claim 1, further comprising applying a physiological filter to said plurality of biosensor output signal values.

14. The method of claim 1, wherein said biosensor comprises a transcutaneous glucose sensor.

15. The method of claim 1, wherein said analyte is glucose.

16. The method of claim 1, wherein said sensor sensitivity value is obtained by extrapolating a line or curve to a fixed background current at zero glucose.

17. The method of claim 16, wherein said background current is calculated to be a fraction or multiple of the biosensor output signal values at zero glucose.

18. A system for calibrating a biosensor that measures an analyte, comprising:

an on-skin sensor control unit; and

a biosensor coupled to said on-skin sensor control unit, wherein said on-skin sensor control unit comprises programming instructions configured to receive a blood analyte concentration;

to receive a plurality of biosensor output signal values;

to apply a median filter to said plurality of biosensor output signal values to obtain a median sensor output value;

to compare said blood analyte concentration with said median sensor output value to obtain a sensor sensitivity value; and

to utilize said sensor sensitivity value to calibrate the signal output of said biosensor.

19. The system of claim 18, wherein said plurality of biosensor output signal values are obtained during a plurality of intervals, and wherein said programming instructions are further configured to apply a median filter that first obtains a median interval sensor output value for each of said plurality of intervals prior to said median filter obtaining a median sensor output value from said median interval sensor output values.

20. The system of claim 18, wherein said plurality of biosensor output signal values are obtained during a plurality of intervals, and wherein said programming instructions are further configured to apply a mean filter that first obtains a mean interval sensor output value for each of said plurality of intervals prior to said median filter obtaining a median sensor output value from said mean interval sensor output values.

21. A method of sensing analyte using a biosensor, comprising:

obtaining a plurality of raw biosensor output signal values;

applying a median filter to said plurality of raw biosensor output signal values to obtain a refined median sensor output value; and

displaying said refined median sensor output value on an electronic monitoring unit coupled to the biosensor.

22. The method of claim 21, wherein said plurality of raw biosensor output signal values are obtained during an interval of 1 minute.

23. The method of claim 21, wherein said plurality of raw biosensor output values are obtained during a plurality of intervals.

24. The method of claim 23, wherein said median filter first obtains a median interval sensor output value for each of said plurality of intervals, and then said median filter obtains a refined median sensor output value from said median interval sensor output values.

25. The method of claim 23, further comprising a mean filter that first obtains a mean interval sensor output value for each of said plurality of intervals, and then said median filter obtains a refined median sensor output value from said mean interval sensor output values.

26. The method of claim 21, further comprising obtaining a value for a background current for said biosensor and subtracting said background current value from said plurality of raw biosensor output signal values or from said refined median sensor output value prior to displaying said refined median sensor output value.

27. The method of claim 21, further comprising applying a physiological filter to said plurality of raw biosensor output signal values.

28. The method of claim 21, wherein said biosensor comprises a transcutaneous glucose sensor.

29. The method of claim 21, wherein said analyte is glucose.

30. A system for sensing analyte using a biosensor, comprising:

an on-skin sensor control unit; and

a biosensor coupled to said on-skin sensor control unit, wherein said on-skin sensor control unit comprises programming instructions configured to receive a plurality of raw biosensor output signal values;

to apply a median filter to said plurality of raw biosensor output signal values to obtain a refined median sensor output value; and

to display said refined median sensor output value on an electronic monitoring unit coupled to the biosensor.

31. The system of claim 30, wherein said plurality of raw biosensor output signal values are obtained during a plurality of intervals, and wherein said programming instructions are further configured to apply a median filter that first obtains a median interval sensor output value for each of said plurality of intervals prior to said median filter obtaining a refined median sensor output value from said median interval sensor output values.

32. The system of claim 30, wherein said plurality of raw biosensor output signal values are obtained during a plurality of intervals, and wherein said programming instructions are further configured to apply a mean filter that first obtains a mean interval sensor output value for each of said plurality of intervals prior to said median filter obtaining a refined median sensor output value from said mean interval sensor output values.