System and method for determining hematocrit insensitive glucose concentration

• US 9,005,426 B2
• Filed: 09/28/2012
• Issued: 04/14/2015
• Est. Priority Date: 09/28/2012
• Status: Active Grant

• Current Assignee: LifeScan IP Holdings, LLC
• Original Assignee: Cilag Gmbh International (Johnson & Johnson)
• Inventors: Malecha, Michael
• Primary Examiner(s): Ball, J. Christopher
• Application Number:
  US13/630,334
• Publication Number:
  US 20140090989A1
• Time in Patent Office: 928 Days
• Field of Search: 20440301-40315, 205/775, 205/787, 205/792
• US Class Current: 205/787
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: G01N 27/3273 Devices therefor, e.g. test element readers, circuitry details not specific to biochemical electrodes G01N33/4875

Abstract

Described are methods and systems to apply a plurality of test voltages to the test strip and measure at least a current transient output resulting from an electrochemical reaction in a test chamber of the test strip so that a glucose concentration can be determined that are generally insensitive to other substances in the body fluid sample that could affect the precision and accuracy of the glucose concentration.

Claims

1. A method of determining blood glucose concentration with a glucose measurement system that comprises 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 at least 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 coupled to the test chamber of the test strip to a strip measurement circuit;

initiating a test sequence after deposition of a sample, in which the initiating comprises;

applying a first voltage of approximately ground potential to the test chamber for a first duration;

applying a second voltage to the test chamber for a second duration after the first duration;

changing the second voltage to a third voltage different from the second voltage for a third duration after the second duration;

switching the third voltage to a fourth voltage different from the third voltage for a fourth duration after the third duration;

altering the fourth voltage to a fifth voltage different from the fourth voltage for a fifth duration after the fourth duration;

modifying the fifth voltage to a sixth voltage different from the fifth voltage for a sixth duration after the fifth duration;

changing the sixth voltage to a seventh voltage different from the sixth voltage for a seventh duration after the sixth duration, wherein each of the second to seventh voltages comprises about one millivolt;

measuring at least one of;

a first current transient output from the test chamber during a first interval proximate the second and third durations;

a second current transient output during a second interval proximate the fourth and fifth durations;

a third current transient output during a third interval proximate the fifth and sixth durations;

a fourth current transient output during a fourth interval proximate the sixth and seventh durations; and

a fifth current transient output during a fifth interval proximate the end of the seventh durations;

calculating a glucose concentration of the sample from at least one of the first, second, third, fourth, or fifth current outputs such that bias in the glucose concentration is less than ±

10% for glucose concentrations less than 75 mg/dL in hematocrits ranging from about 20% to about 60%.

2. The method of claim 1, in which the second voltage comprises a voltage opposite in polarity to the third, fifth and seventh voltages and with the same polarity as the fourth and sixth voltages.

3. The method of claim 1, in which the calculating comprises utilizing an equation of the form:

4. The method of claim 1, in which the calculating comprises utilizing an equation of the form

5. The method of claim 1, in which the calculating comprises utilizing an equation of the form

6. The method of claim 1, in which the calculating comprises utilizing an equation of the form

7. The method of claim 1, in which the calculating comprises utilizing an equation of the form

8. A method of determining blood glucose concentration with a glucose measurement system that comprises 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 at least 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 coupled to the test chamber of the test strip to a strip measurement circuit;

initiating a test sequence after deposition of a sample, in which the initiating comprises;

applying a zero potential for a first duration to the test chamber;

driving a plurality of voltages to the test chamber over a plurality of durations after the first duration in which at least one millivolt for one duration is opposite in polarity to another voltage in another duration after the one duration such that the change in polarity produces a plurality of inflections in a current output transient of the test chamber;

measuring magnitudes of the current output transient proximate respective inflections of the current transient caused by the change in polarity in the plurality of voltages, wherein the plurality of voltages comprises two voltages of equal magnitude but opposite in polarity; and

the measuring comprises summing current outputs of a decay of the current transient during an interval proximate the decay of the current transient; and

calculating a glucose concentration of the sample from magnitudes of the current transient of the measuring step.

9. The method of claim 8, in which the plurality of durations comprises second, third, fourth, fifth, sixth, and seventh durations after the first duration.

10. The method of claim 9, in which the calculating comprises utilizing an equation of the form:

11. The method of claim 9, in which the calculating comprises utilizing an equation of the form

12. The method of claim 9, in which the calculating comprises utilizing an equation of the form

13. The method of claim 9, in which the calculating comprises utilizing an equation of the form

14. The method of claim 9, in which the calculating comprises utilizing an equation of the form

15. 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 a 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 so that, when the test strip is inserted into the strip port connector and a blood sample is deposited in the test chamber for chemical transformations of glucose in the blood sample, a glucose concentration of the blood sample is determined by the microcontroller from at least one of the first, second, third, fourth, or fifth current outputs from the test chamber due to applied voltages such that bias in the glucose concentration is less than ±

10% for glucose concentrations less than 75 mg/dL in hematocrits ranging from about 20% to about 60%, in which the microcontroller calculates glucose concentration with an equation of the form;

utilizing an equation of the form

16. 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 a 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 so that, when the test strip is inserted into the strip port connector and a blood sample is deposited in the test chamber for chemical transformations of glucose in the blood sample, a glucose concentration of the blood sample is determined by the microcontroller from at least one of the first, second, third, fourth, or fifth current outputs from the test chamber due to applied voltages such that bias in the glucose concentration is less than ±

10% for glucose concentrations less than 75 mg/dL in hematocrits ranging from about 20% to about 60%, which the microcontroller calculates glucose concentration with an equation of the form;