Error detection in analyte measurements based on measurement of system resistance

• US 7,517,439 B2
• Filed: 04/15/2005
• Issued: 04/14/2009
• Est. Priority Date: 04/15/2005
• Status: Active Grant

• Current Assignee: Agamatrix Incorporated (AgaMatrix Holdings LLC d/b/a WaveForm Diabetes)
• Original Assignee: Agamatrix Incorporated (AgaMatrix Holdings LLC d/b/a WaveForm Diabetes)
• Inventors: Williams, Richard, Diamond, Steven, Harding, Ian
• Primary Examiner(s): Noguerola; Alex
• Assistant Examiner(s): Ball; J. Christopher
• Application Number:
  US10/907,817
• Publication Number:
  US 20060231424A1
• Time in Patent Office: 1,460 Days
• Field of Search: 205/792, 205/775, 204/401, 204/775
• US Class Current: 204/401
• CPC Class Codes: C12Q 1/006 for glucose
• CPC Class Codes: G01N 27/3273 Devices therefor, e.g. test element readers, circuitry details not specific to biochemical electrodes G01N33/4875

Abstract

Measurement of the series resistance of a working and counter electrode pair in an electrochemical test strip provide error detection for multiple variations in the quality of the test strip, as well as the operation of strip in the test meter. In particular, a single measurement of series resistance can be used to detect and generate an error message when an incorrect reading is likely to result due to (1) damaged electrode tracks, (2) fouled electrode surfaces, (3) dirty strip contacts, or (4) short circuit between the electrodes.

Claims

1. A method for determination of an analyte in a sample comprising the steps of:

(a) introducing the sample to an electrochemical test strip having working and counter electrodes;

(b) applying a potential difference, V_app, between the electrodes of the test strip and observing a current signal sufficient to provide a determination of analyte in the sample;

(c) switching off the applied potential at time t_switch, and determining the magnitude, V_drop, of a voltage drop occurring immediately after t_switch, wherein the magnitude of V_drop, if present, is indicative of the magnitude of series electrode resistance;

(d) checking the determined magnitude of V_drop against a predetermined range, and rejecting the test if the magnitude of V_drop falls outside of the range, and

(e) if the magnitude is within the predetermined range, proceeding to display or communicate the result from the determination of analyte.

2. The method of claim 1, wherein V_drop is defined as the difference in potential between V_app and the potential measured at a predetermined time after t_switch.

3. The method of claim 1, wherein V_elect is defined as the difference in potential between V_app and the electrochemical potential, V_elect.

4. The method of claim 3, wherein V_elect is determined by extrapolating voltage decay observed in a time interval after t_switch when decrease in potential associated with series electrode resistance has occurred and determining the extrapolated value of potential at time t_switch.

5. The method of claim 4, wherein the time interval after t_switch starts at from 0.5 to 2 milliseconds after t_switch.

6. The method of claim 5, wherein the time interval after t_switch starts at 1 millisecond after t_switch.

8. The method of claim 2, wherein the predetermined time after t_switch is about 1 millisecond.

7. A method for detecting erroneous conditions in an analyte determination in an electrochemical test strip comprising determining the magnitude of series electrode resistance during analyte determination, checking the determined magnitude against a predetermined range, and rejecting the test if the magnitude of series electrode resistance is outside of the range.