ANALYTE MEASUREMENT TECHNIQUE AND SYSTEM

• US 20130284611A1
• Filed: 04/30/2012
• Published: 10/31/2013
• Est. Priority Date: 04/30/2012
• Status: Active Grant

• Current Assignee: LifeScan IP Holdings, LLC
• Original Assignee: Cilag Gmbh International (Johnson & Johnson)
• Inventors: MATZINGER, David
• Granted Patent: US 8,709,232 B2
• Time in Patent Office: Days
• US Class Current: 205/782
• CPC Class Codes: G01N 27/3274 Corrective measures, e.g. error detection, compensation for temperature or hematocrit, calibration coding of calibration information G01N33/48771

Abstract

Described are methods and systems to apply a plurality of test voltages to the test strip and measure a current transient output resulting from an electrochemical reaction in a test chamber of the test strip so that highly accurate glucose concentration can be determined.

Claims

1. A method of determining blood glucose concentration with a glucose measurement system that includes a test strip and test meter, the test meter having a microcontroller configured to apply a plurality of test voltages to the test strip and measure a current transient output resulting from an electrochemical reaction in a test chamber of the test strip, the method comprising:

inserting the test strip into a strip port connector of the test meter to connect at least two electrodes of the test strip to a strip measurement circuit;

initiating a test sequence after deposition of a sample;

applying a first voltage for a first time duration;

switching the first voltage to a second voltage different than the first voltage;

changing the second voltage to a third voltage different from the second voltage;

measuring a second current output of the current transient from the electrodes after the changing from the second voltage to the third voltage;

estimating a current that approximates a steady state current output of the current transient after the third voltage is maintained at the electrodes;

calculating a blood glucose concentration based on the first, second and third current output of the current transient with an equation of the form;

2. The method of claim 1, in which the measuring of the first current output comprises measuring a current output of the at least two electrodes at about 1.1 seconds after initiation of the test sequence.

3. The method of claim 2, in which the measuring of the second current output comprises measuring a current output of the at least two electrodes at about 4.1 seconds after initiation of the test sequence.

4. The method of claim 2, in which the estimating of the steady state current output comprises measuring a current output of the at least two electrodes at about 5 seconds after initiation of the test sequence.

5. The method of claim 1, in which the manufacturing parameter a′

comprises approximately 0.14, b′

comprises approximately 4.9, c comprises approximately 4.24, d comprises approximately 11.28, p′

comprises approximately 0.548, and zgr′

comprises approximately 9.38.

6. A method of determining blood glucose concentration with a glucose measurement system that includes a test strip and test meter, the test meter having a microcontroller configured to apply a plurality of test voltages to the test strip and measure a current transient output resulting from an electrochemical reaction in a test chamber of the test strip, the method comprising:

inserting the test strip into a strip port connector of the test meter to connect at least two electrodes of the test strip to a strip measurement circuit;

initiating a test sequence after deposition of a sample;

applying a first voltage;

switching the first voltage to a second voltage different than the first voltage;

changing the second voltage to a third voltage different from the second voltage;

measuring a second current output of the current transient from the electrodes after the changing from the second voltage to the third voltage;

estimating a current that approximates a steady state current output of the current transient after the third voltage is maintained at the electrodes;

deriving an initial glucose proportional current based on the first current, second current, and estimated current;

formulating a hematocrit compensation factor based on the initial glucose proportional current; and

calculating a glucose concentration from the derived initial glucose proportional current and the hematocrit compensation factor.

7. The method according to claim 6, in which the deriving comprises calculating the initial glucose proportional current i2corr′

based on the following equation;

8. The method of claim 7, in which i_4.1 comprises the current measured at about 4.1 seconds after initiation of the test sequence, i₅ comprises the current measured at about 5 seconds after initiation of the test sequence;

and i_1.1 comprises the current measured at about 1.1 seconds after initiation of the test sequence.

9. The method according to claim 7, in which the hematocrit compensation factor comprises a ratio of the initial glucose proportional current divided by an integration of current outputs during application of the second voltage less an offset based on a current output measured during application of the second voltage.

10. The method according to claim 9, in which the hematocrit compensation factor is of the form:

11. The method of claim 10, in which the calculating comprises utilizing an equation of the form:

12. A blood glucose measurement system comprising:

an analyte test strip including;

a substrate having a reagent disposed thereon;

at least two electrodes proximate the reagent in test chamber;

an analyte meter including;

a strip port connector disposed to connect to the two electrodes;

a power supply; and

a microcontroller electrically coupled to the strip port connector and the power supply, the microcontroller programmed to determine a glucose concentration G₁ based on a hematocrit compensation factor and initial glucose proportional current in which the hematocrit compensation factor comprises a ratio that includes the initial glucose proportional current so that at least 97% of corrected test results are within respective bias criterion of ±

10 mg/dL at 65 mg/dL, 240 mg/dL, or at 450 mg/dL as compared to reference YSI data;

±

12 mg/dL at 65 mg/dL, 240 mg/dL, or 450 mg/dL as compared to reference YSI data; and

±

15 mg/dL at 65 mg/dL, 240 mg/dL, or 450 mg/dL as compared to reference YSI data.

13. The system of claim 12, in which the manufacturing parameters a′

, b′

, c, d, p′

, zgr′

are such that a′

comprises approximately 0.14, b′

comprises approximately 4.9, c comprises approximately 4.24, d comprises approximately 11.28. p′

comprises approximately 0.548 and zgr′

comprises approximately 9.38.

14. A method of determining a hematocrit compensation factor with a glucose measurement system that includes a test strip and test meter, the test meter having a microcontroller configured to apply a plurality of test voltages to the test strip and measure a current transient output resulting from an electrochemical reaction in a test chamber of the test strip, the method comprising:

initiating a test sequence after deposition of a sample;

applying a first voltage;

measuring a plurality of current outputs from the test chamber;

deriving an initial glucose proportional current based on the plurality of measured current outputs; and

formulating a hematocrit compensation factor based on the derived initial glucose proportional current.

15. The method of claim 14, in which the formulating a hematocrit compensation factor comprises dividing the derived initial glucose proportional current by initial glucose proportional current and integration of current outputs during application of a second voltage.

16. The method of claim 15, in which the integration includes an offset to the integration based on a measured current during application of a second voltage.

17. The method of claim 16, further comprising the step of calculating a glucose concentration based on a compensation of the derived initial glucose proportional current with the hematocrit compensation factor.

18. The method of claim 17, in which the hematocrit compensation factor is of the form:

19. The method of claim 18, in which the calculating comprises utilizing an equation of the form: