Method for determining hematocrit corrected analyte concentrations

• US 9,046,480 B2
• Filed: 03/04/2013
• Issued: 06/02/2015
• Est. Priority Date: 10/05/2006
• Status: Expired due to Fees

• Current Assignee: Cilag Gmbh International (Johnson & Johnson)
• Original Assignee: LifeScan Scotland Limited (Johnson & Johnson)
• Inventors: Cardosi, Marco F., Gill, Andrew, Mills, Leanne, Leach, Christopher Philip, Blythe, Stephen Patrick
• Primary Examiner(s): Ball, J. Christopher
• Application Number:
  US13/783,807
• Publication Number:
  US 20130240375A1
• Time in Patent Office: 820 Days
• Field of Search: 205/775, 205/777.5, 205/778, 205/792, 20440301-40315, 435/4, 435/14, 435 25- 28, 600/345, 600/347
• US Class Current: 1/1
• CPC Class Codes: C12Q 1/006 for glucose
• CPC Class Codes: G01N 27/3271 Amperometric enzyme electrodes for analytes in body fluids, e.g. glucose in blood amperometry per se G01N27/49; aspects concerning the enzyme reagent C12Q1/001
• 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

The method includes: providing a test strip comprising a reference electrode and a working electrode coated with a reagent layer; applying a fluid sample to the test strip for a reaction period; applying a test voltage between the reference electrode and the working electrode; measuring a test current as a function of time; measuring a steady state current value when the test current has reached an equilibrium; calculating a ratio of the test current to the steady state current value; plotting the ratio of the test current to the steady state current value as a function of the inverse square root of time; calculating an effective diffusion coefficient from the slope of the linearly regressed plot of the ratio of the test current to the steady state current value as a function of the inverse square root of time; and calculating a hematocrit-corrected concentration of analyte.

Claims

1. A method of calculating a hematocrit-corrected glucose concentration in a fluid sample, the method comprising:

providing a test strip comprising a reference electrode and a working electrode formed with a plurality of microelectrodes and coated with a reagent layer;

applying a fluid sample to the test strip for a reaction period;

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

measuring a test current as a function of time;

measuring a steady state current value when the test current has reached an equilibrium;

calculating a ratio of the test current to the steady state current value;

plotting the ratio of the test current to the steady state current value as a function of the inverse square root of time;

calculating an effective diffusion coefficient from the slope of the linearly regressed plot of the ratio of the test current to the steady state current value as a function of the inverse square root of time;

substituting the estimated diffusion coefficient into an equation of the form;

2. The method of claim 1, wherein the calculating of the effective diffusion coefficient step utilizes an equation of the form:

3. The method of claim 1, wherein the test strip further comprises an insulation portion disposed on the plurality of microelectrodes and the insulation portion has a height between about one micron and about six microns.

4. The method of claim 1, wherein the reference electrode and the working electrode are comprised of gold.

5. The method of claim 1, wherein the reagent layer comprises an enzyme, a mediator and a buffering agent wherein the mediator comprises ruthenium (III) hexamine.

6. The method of claim 1, wherein the diameter of each of the plurality of microlectrodes is between about 5 microns and about 50 microns.

7. The method of claim 1, wherein each of the plurality of micoelectrodes is spaced apart by a distance ranging from about 5 to about 10 times the diameter of a microelectrode.

8. The method of claim 1, wherein each of the plurality of microelectrodes is spaced apart by a distance ranging from about 25 microns to about 500 microns.

9. The method of claim 1, wherein the shape of each of the plurality of microelectrodes is selected from a group consisting essentially of a circle, a square, a rectangle, an oval and an ellipse and combinations thereof.