Systems and methods for high accuracy analyte measurement

• US 10,371,663 B2
• Filed: 03/13/2017
• Issued: 08/06/2019
• Est. Priority Date: 12/31/2010
• Status: Active Grant

• Current Assignee: LifeScan IP Holdings, LLC
• Original Assignee: LifeScan IP Holdings, LLC
• Inventors: Chatelier, Ronald C., Hodges, Alastair M.
• Primary Examiner(s): Noguerola, Alexander S
• Application Number:
  US15/457,133
• Publication Number:
  US 20170184542A1
• Time in Patent Office: 876 Days
• CPC Class Codes: C12Q 1/006 for glucose
• CPC Class Codes: C12Q 1/025 for testing or evaluating the effect of chemical or biological compounds, e.g. drugs, cosmetics antimicrobial activity C12Q1/18
• CPC Class Codes: G01N 27/30 Electrodes, e.g. test electrodes; Half-cells G01N27/414 takes precedence
• CPC Class Codes: G01N 27/327 Biochemical electrodes , e.g. electrical or mechanical details for in vitro measurements
• CPC Class Codes: G01N 27/3272 Test elements therefor, i.e. disposable laminated substrates with electrodes, reagent and channels optical biosensors G01N33/52
• 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 27/413 Concentration cells using liquid electrolytes measuring currents or voltages in voltaic cells
• CPC Class Codes: G01N 27/4163 checking the operation of, or calibrating, the measuring apparatus G01N27/3274, G01N27/4175 and G01N33/0006 take precedence
• CPC Class Codes: G01N 33/49 Blood chemical methods for determining blood cell populations G01N33/5094; chemical analysis of blood groups or blood types G01N33/80

Abstract

Methods for determining a concentration of an analyte in a sample, and the devices and systems used in conjunction with the same, are provided herein. In one exemplary embodiment of a method for determining a concentration of an analyte in a sample, a sample including an analyte is provided in a sample analyzing device having a working and a counter electrode. An electric potential is applied between the electrodes and a first analyte concentration is determined. A second analyte concentration value is calculated from the first analyte concentration value and corrected for temperature effects, fill time and capacitance to provide for a final analyte concentration value.

Claims

1. An analyte measurement system comprising:

a plurality of test strips, each test strip having one or more adhesive layers, at least two electrodes spaced apart in a test chamber and a reagent disposed therebetween to receive a sample containing an analyte; and

an analyte measurement device including;

a strip port having connectors configured to mate with respective electrodes of each test strip; and

a microprocessor coupled to the strip port and configured to measure current, test strip capacitance, and sample fill time with the electrodes of each test strip when a referential sample is deposited in the test chamber of each of the plurality of test strips and a corrected final concentration determined based on the current, sample fill time, and the test strip capacitance so that a percentage of the corrected final concentration value from the plurality of test strips are within 10% of a referential analyte value above a threshold analyte value, in which the microprocessor is configured so that when an analyte test strip of the plurality of test strips is coupled to the strip port with a sample deposited therein, an analyte in the sample reacts between the two electrodes to provide for a first analyte concentration value G1 based on measured output current values over discrete intervals, a second analyte concentration value G2 based on measured output current values over discrete intervals, a temperature corrected analyte concentration value G3 from the second analyte concentration value G2, a sample fill time corrected analyte concentration value G4 from the temperature corrected analyte concentration value, and a test strip capacitance corrected final concentration value G5 from the sample fill time corrected analyte concentration value G4, wherein the test strip capacitance is a function of a slow flow of the one or more adhesive layers into the test chamber.

2. The system of claim 1, in which the discrete intervals comprise a first interval from about 3.9 seconds to about 4 seconds and a second interval from about 4.25 seconds to about 5 seconds, the first and second intervals being measured from the time a sample is deposited in the test chamber, wherein the output current values measured over the first and second intervals comprise a first current summation i_r and a second current summation i_l, where:

3. The system of claim 2, in which the first analyte concentration value G1 comprises derivation of the current values with an equation of the form:

4. The system of claim 3, in which i₂ is determined using an equation of the form:

5. The system of claim 3, in which i_ss is determined using an equation of the form:

6. The system of claim 3, in which the temperature corrected analyte concentration value G3 is corrected by a fill time correction factor based on a fill time, the fill time correction factor is about zero when the fill time is less than a first fill time threshold and when the fill time is greater than the first fill time threshold and less than a second fill time threshold, the fill time correction factor is calculated based on the fill time and when the fill time is greater than the second fill time threshold, the fill time correction factor comprises a constant value.

7. The system of claim 3, in which the temperature corrected analyte concentration value G3 comprises a first temperature correction to the second analyte concentration value G2 whenever an ambient temperature is greater than first temperature threshold and a second temperature correction whenever the ambient temperature is less than to the first temperature threshold.

8. The system of claim 3, in which the test strip capacitance corrected final concentration value G5 is set to equal to the sample fill time corrected analyte concentration value when the sample fill-time corrected analyte concentration value G4 is less than a first concentration threshold.

9. The system of claim 2, in which the second analyte concentration value G2 comprises derivation with an equation of the form:

10. The system of claim 1, in which the test strip capacitance corrected final concentration value G5 comprises a product of a capacitance correction factor and the sample fill-time corrected analyte concentration value G4 when the sample fill-time corrected analyte concentration value G4 is greater than a first concentration threshold, the capacitance correction factor for the corrected final concentration value being based on a measured capacitance when the capacitance is less than a first capacitance threshold and the capacitance correction factor is set to a maximum value when the capacitance correction factor is greater than a set value.

11. A method for determining a concentration of an analyte in a sample, the method comprising:

introducing a sample including an analyte to an electrochemical sensor having one or more adhesive layers, the electrochemical sensor including a reaction chamber comprising two electrodes in a spaced apart configuration; and

reacting the analyte to cause a physical transformation of the analyte between the two electrodes;

determining a concentration of the analyte that is corrected for a physical property of the electrochemical sensor using a correction factor that is based on a capacitance of the electrochemical sensor, wherein the capacitance is a function of a slow flow of the one or more adhesive layers into the reaction chamber;

wherein the method achieves an accuracy standard of at least ±

10% for analyte concentrations above an analyte concentration threshold or at least ±

10 mg/dL below an analyte concentration threshold, such that at least 95% of a series of analyte concentration evaluations yield an analyte concentration value that is accurate to within 10% of a reference analyte measurement.

12. The method of claim 11, wherein the analyte concentration threshold is about 75 mg/dL.

13. The method of claim 11, wherein the step of determining a concentration of the analyte further includes a step of correcting for one or more of a fill time of the sample, a temperature of the sample, a temperature of the electrochemical sensor, and glucose reaction kinetics.

14. The method of claim 13, wherein the step of correcting for glucose reaction kinetics includes:

calculating a first analyte concentration, and

calculating a second analyte concentration that depends on the first analyte concentration, such that the magnitude of the correction for glucose reaction kinetics is proportional to the magnitude of the first analyte concentration.

15. The method of claim 13, wherein the physical property of the electrochemical sensor is related to at least one of an age of the electrochemical sensor and a storage condition of the electrochemical sensor.

16. The method of claim 11, wherein the two electrodes comprise one of an opposing faced orientation or a facing orientation.

17. The method of claim 11, wherein the electrochemical sensor comprises a glucose sensor and the analyte comprises glucose.

18. The method of claim 11, wherein the sample comprises one of blood or whole blood.

19. A method for measuring a corrected analyte concentration in a sample, the method comprising:

detecting a presence of the sample in an electrochemical sensor, the

electrochemical sensor comprising two electrodes and one or more adhesive layers;

reacting an analyte in a reaction chamber to cause a physical transformation of the analyte;

determining a first analyte concentration in the sample; and

calculating a corrected analyte concentration based on the first analyte concentration and one or more correction factors, the one or more correction factors including a correction factor calculated in view of a physical property of the electrochemical sensor, wherein the one or more correction factors includes a correction factor based on a measured capacitance of the electrochemical sensor, the measured capacitance being a function of a slow flow of the one or more adhesive layers into the reaction chamber.

20. The method of claim 19, wherein the one or more correction factors further include correction factors calculated in view of at least one of a fill time of the sample, a temperature of the sample, and a temperature of the electrochemical sensor.

21. The method of claim 19, wherein the physical property of the electrochemical sensor is related to at least one of an age of the electrochemical sensor and a storage condition of the electrochemical sensor that induces the slow flow of the one of more adhesive layers.

22. The method of claim 19, further comprising correcting for glucose reaction kinetics, wherein correcting for glucose reaction kinetics includes calculating a second analyte concentration that depends on the first analyte concentration, such that the magnitude of the correction for glucose reaction kinetics is proportional to the magnitude of the first analyte concentration.

23. The method of claim 19, wherein the two electrodes comprise an opposing faced orientation or a facing orientation.

24. An electrochemical system, comprising:

an electrochemical sensor including electrical contacts configured to mate with a test meter, the electrochemical sensor comprising;

a reaction chamber inclusing a first electrode and a second electrode in a spaced apart relationship,

one or more adhesive layers, and

a reagent; and

the test meter including a processor configured to receive current data from the electrochemical sensor upon application of voltages to the electrochemical sensor, and further configured to determine a corrected analyte concentration based on a correction factor to correct for a physical property of the electrochemical sensor, wherein the correction factor is based on a measured capacitance of the electrochemical sensor, the measured capacitance being a function of a slow flow of the one or more adhesive layers into the reaction chamber, and one or more of a fill time of a sample, a temperature of the sample, a temperature of the electrochemical sensor, and glucose reaction kinetics.

25. The electrochemical system of claim 24, wherein the test meter includes data storage containing an analyte concentration threshold and a plurality of thresholds related to one or more of a fill time of the sample, a physical property of the electrochemical sensor, a temperature of the sample, a temperature of the electrochemical sensor, and glucose reaction kinetics.

26. The electrochemical system of claim 24, wherein the system achieves an accuracy standard of at least ±

10% for analyte concentrations above an analyte concentration threshold or at least ±

10 mg/dL for concentrations below an analyte concentration threshold, such that at least 95% of a series of analyte concentration evaluations yield an analyte concentration value that is accurate to within 10% of a reference analyte measurement.

27. The electrochemical system of claim 24, wherein the electrochemical sensor comprises a glucose sensor and the analyte comprises glucose.

28. The electrochemical system of claim 24, wherein at least one of the electrochemical sensor, the test meter, and the processor are configured to measure a temperature of the sample.

29. The electrochemical system of claim 24, wherein the sample comprises blood or whole blood.

30. The electrochemical system of claim 24, in which the first and second electrodes comprise an opposing faced orientation or a facing orientation.