Systems and methods for determining a substantially hematocrit independent analyte concentration

• US 8,293,096 B2
• Filed: 01/22/2010
• Issued: 10/23/2012
• 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., Blythe, Stephen Patrick, Finch, Matthew, Bailey, Eric Jason, Anderson, Gretchen, Comstock, Lorraine, McEvoy, Mary, Sutton, Thomas, Day, Richard Michael, Mills, Leanne, Day, Emma Vanessa Jayne, Leach, Christopher Philip, Thompson, Arlene, Naylor, Nina Antonia, Dolan, Michael Patrick
• Primary Examiner(s): Olsen, Kaj K
• Application Number:
  US12/692,120
• Publication Number:
  US 20110162978A1
• Time in Patent Office: 1,005 Days
• Field of Search: 204/403.01, 204/403.02, 205/777.5, 205/778, 205/792
• US Class Current: 205/792
• 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

A method and system is provided to allow for determination of substantially Hematocrit independent analyte concentration. In one example, an analyte measurement system is provided that includes a test strip and a test meter. The test strip includes a reference electrode and a working electrode, in which the working electrode is coated with a reagent layer. The test meter includes an electronic circuit and a signal processor. The electronic circuit applies a plurality of voltages to the reference electrode and the working electrode over respective durations. The signal processor is configured to determine a substantially hematocrit-independent concentration of the analyte from a plurality of current values as measured by the processor upon application of a plurality of test voltages to the reference and working electrodes over a plurality of durations interspersed with rest voltages lower than the test voltages being applied to the electrodes.

Claims

1. A method of determining a substantially hematocrit-independent concentration of an analyte in a fluid sample deposited on a test strip having a reference electrode and a working electrode, in which the working electrode is coated with a reagent layer, the method comprising:

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

applying a first test voltage to the reference electrode and the working electrode and measuring a first current value therebetween, the first test voltage being an absolute value from about 100 millivolts to about 600 millivolts;

applying a first rest voltage between the reference electrode and the working electrode, the first rest voltage is an absolute value from about zero to about 50 millivolts;

applying a second test voltage between the reference electrode and the working electrode and measuring a second current value, in which the second test voltage is an absolute value from about 100 millivolts to about 600 millivolts;

applying a second rest voltage between the reference electrode and the working electrode, in which the second rest voltage is an absolute value from about zero to about 50 millivolts;

applying a third test voltage between the reference electrode and the working electrode and measuring a third current value, in which the third test voltage is an absolute value from about 100 millivolts to about 600 millivolts; and

calculating substantially hematocrit-independent concentration of the analyte from the first, second and third current values, in which the calculating comprises calculating the substantially hematocrit-independent concentration of the analyte from the y-intercept of a graph representing log₁₀(I_i) versus log₁₀(time);

where;

I_i is the current value measured near the end of each test voltage and i ranges from about 1 to about 3; and

time is the time at which I_i is measured.

2. The method of claim 1, in which the duration of the first, second and third test voltages is equal and ranges from about 0.1 to about 1.0 seconds;

the duration of the first and second rest voltages is equal and ranges from about 0.05 to about 1.0 seconds;

the first, second and third current values are measured at about 0.1 to about 1.0 seconds after a test voltage is applied to the test strip;

the magnitude of the first, second and third test voltages is equal and is one of about 200 millivolts or about 400 millivolts; and

the reaction period is from about zero seconds to about five seconds.

3. The method of claim 1, in which the working electrode comprises a plurality of microelectrodes formed from gold.

4. The method of claim 1, in which the reagent layer comprises an enzyme, a mediator and a buffering solution in which the mediator is ruthenium hexamine chloride ranging in amount from about 15 percent to about 20 percent based on a ratio of a weight of the mediator to a volume of the buffering solution.

5. The method of claim 1, further comprising:

calculating a hematocrit fraction using the follow equation;

6. The method of claim 5, in which the duration of the first, second and third test voltages is equal and ranges from about 0.1 to about 1.0 seconds;

the duration of the first and second rest voltages is equal and ranges from about 0.05 to about 1.0 seconds;

the first, second and third current values are measured at about 0.1 to about 1.0 seconds after a test voltage is applied to the test strip;

the magnitude of the first, second and third test voltages is equal and is one of about 200 millivolts or about 400 millivolts; and

the reaction period is from about zero seconds to about five seconds.