METHODS FOR DETERMINING AN ANALYTE CONCENTRATION USING SIGNAL PROCESSING ALGORITHMS

• US 20110005941A1
• Filed: 09/03/2009
• Published: 01/13/2011
• Est. Priority Date: 10/05/2006
• Status: Active Grant

• Current Assignee: Cilag Gmbh International (Johnson & Johnson)
• Original Assignee: LifeScan Scotland Limited (Johnson & Johnson)
• Inventors: Day, Emma Vanessa Jayne, Alvarez-Icaza, Manuel, BLYTHE, Stephen Patrick, Mills, Leanne, Day, Richard Michael, Leach, Christopher Philip, Cardosi, Marco F.
• Granted Patent: US 8,460,537 B2
• Time in Patent Office: Days
• US Class Current: 205/777.5
• CPC Class Codes: G01N 27/3273 Devices therefor, e.g. test element readers, circuitry details not specific to biochemical electrodes G01N33/4875

Abstract

A method for determining an analyte concentration in blood is described that reduces the effects of hematocrit using a test strip attached to a test meter. The test strip includes a working electrode and a reference electrode. The test meter applies a test voltage between the working electrode and the reference electrode. After a user applies a blood sample containing an analyte onto the test strip, the test meter measures a plurality of test currents for a test time interval.

Claims

1. A method for determining an analyte concentration using a test strip having a working electrode and a reference electrode, the method comprising:

applying a test voltage between the working electrode and the reference electrode;

measuring a plurality of test currents with the test meter when a blood sample containing the analyte is applied to the test strip;

adding a first portion of the plurality of test currents together over a first pre-determined time interval to form a first total; and

subtracting each of the plurality of test currents within a second portion from the first total to form a second total such that the second total is correlated to the analyte concentration.

2. A method for determining an analyte concentration using a test strip having a working electrode and a reference electrode, the method comprising:

applying a test voltage between the working electrode and the reference electrode;

measuring a plurality of test currents when a blood sample containing the analyte is applied to the test strip;

calculating an analyte correlation value (Y) using an equation which is

3. A method for determining an analyte concentration using a test strip having a working electrode and a reference electrode, the method comprising:

applying a test voltage between the working electrode and the reference electrode;

measuring a plurality of test currents when a blood sample containing the analyte is applied to the test strip;

calculating a first total of the test currents over a first pre-determined time interval;

multiplying the first total by a first correction factor calculating a second total of the test currents over a second pre-determined time interval;

multiplying the second total by a second correction factor;

summing together the first total and the second total to form an aggregate, wherein the aggregate is correlated to the analyte concentration.

4. The method of claim 3, wherein the second correction factor is about equal to the first correction factor multiplied by −

1.

5. A method for determining an analyte concentration using a test strip having a working electrode and a reference electrode, the method comprising:

applying a test voltage between the working electrode and the reference electrode;

measuring a plurality of test currents for a test time interval after a blood sample containing the analyte is applied to the test strip;

calculating an analyte correlation value (Y) using an equation which is

6. The method of claim 5, wherein the method further comprises the step of calculating the ending point and starting point of the first pre-determined time interval, the second pre-determined time interval, and the third pre-determined time interval (t_F1, t_L1, t_F2, t_L2, t_F3, and t_L3) using an error minimization function S, wherein the error minimization function S is based on a background sensitivity function a(t), glucose sensitivity function b(t), and hematocrit sensitivity function c(t).

7. The method of claim 6, wherein the error minimization function S is

S=[∫

a(t)c(t)q(t)dt]²+[∫

b(t)c(t)q(t)dt]²≈

0.

8. The method of claim 5, wherein a duration of the first pre-determined time interval, the second pre-determined time interval, and the third pre-determined time interval are calculated by minimizing the effects of hematocrit.

9. The method of claim 5, wherein a sum of a duration of the first pre-determined time interval and of the third pre-determined time interval does not equal the second pre-determined time interval.

10. The method of claim 5, wherein a sum of a duration of the first pre-determined time interval and of the third pre-determined time interval equals the second pre-determined time interval.

11. The method of claim 5, wherein the analyte correlation value (Y) is calculated during the test time interval, whereby a microprocessor in the test meter can calculate the analyte concentration faster than if the test meter calculates the analyte correlation value (Y) after the test time interval.

12. The method of claim 5 further comprising the step of:

determining a maximum peak time from the plurality of test current;

determining an ending point of a first pre-determined time interval by multiplying the maximum peak time times a calibration factor.

13. The method of claim 12, wherein the calibration factor ranges from about 0.5 to about less than one.

14. The method of claim 5, wherein a reagent layer is disposed over the working electrode, the reagent layer comprising:

an enzyme;

a ruthenium hexamine mediator; and

a buffer for dissolving the enzyme and the ruthenium hexamine mediator;

wherein the ruthenium hexamine has a concentration range from about 15% to about 20% (weight/volume).

15. The system of claim 14, wherein the enzyme is a material selected from the group consisting of glucose oxidase and glucose dehydrogenase.

16. The system of claim 14, wherein the buffer is a chemical selected from the group consisting of phosphate, citrate, and citraconate.

17. The system of claim 14, wherein the buffer is phosphate and has a pH of about 7.

18. The system of claim 14, wherein the formulation further comprises a filler having hydrophilic and hydrophobic domains.

19. The system of claim 14, wherein the filler comprises silica modified by surface treatment with methyl dichlorosilane.

20. The system of claim 14, wherein the formulation is printed on the working electrode via a screen that secures a plurality of interwoven threads, the plurality of interwoven threads defining a plurality of open rectangular spaces for allowing the formulation to pass therethrough, the plurality of interwoven threads having a thread spacing and a thread diameter, wherein the thread spacing ranges from about 90 threads per centimeter to about 120 threads per centimeter and the thread diameter may range from about 30 microns to about 50 microns.

21. The method of claim 5, wherein the working electrode comprises microelectrode array.

22. The method of claim 5, wherein the test strip further comprises an integrated lance.

23. A system for determining an analyte concentration, the system comprising:

a test meter; and

a test strip comprising a working electrode and a reference electrode in which the test strip is configured to be inserted into the test meter so that the test meter applies a test voltage between the working electrode and the reference electrode and determines a plurality of test currents for a test time interval after a blood sample containing the analyte is applied to the test strip to determine an analyte concentration based on an analyte correlation value (Y), where the analyte correlation value (Y) is defined by an equation which is