Dual Frequency Impedance Measurement of Hematocrit in Strips

• US 20120111739A1
• Filed: 10/08/2008
• Published: 05/10/2012
• Est. Priority Date: 10/08/2008
• Status: Abandoned Application

• Current Assignee: Nipro Diagnostics, Inc.
• Original Assignee: Nipro Diagnostics, Inc.
• Inventors: Carlson, Angela, Pasqua, John J., Shields, Christine
• Application Number:
  US12/247,563
• Publication Number:
  US 20120111739A1
• Time in Patent Office: Days
• US Class Current: 205/777.5
• CPC Class Codes: G01N 27/07 Construction of measuring vessels; Electrodes therefor
• CPC Class Codes: G01N 27/3272 Test elements therefor, i.e. disposable laminated substrates with electrodes, reagent and channels optical biosensors G01N33/52
• CPC Class Codes: G01N 27/3273 Devices therefor, e.g. test element readers, circuitry details not specific to biochemical electrodes G01N33/4875
• CPC Class Codes: G01N 33/48757 Test elements dispensed from a stack
• CPC Class Codes: G01N 33/49 Blood chemical methods for determining blood cell populations G01N33/5094; chemical analysis of blood groups or blood types G01N33/80

Abstract

This invention is a method for determining a hematocrit value. The steps include applying a first pulse of potential excitation at a first frequency to a test strip containing a fluid sample. The method also includes applying a second pulse at a second frequency that is higher than the first frequency. Based on first and second impedance measurements associated with each pulse, a hematocrit value may be determined. Also, a concentration of an analyte contained within the fluid sample may be determined based on the hematocrit value.

Claims

1. A method for determining a hematocrit value of a sample fluid, comprising:

providing a sample fluid to a test strip;

applying to the test strip a first pulse at a first frequency and a second pulse at a second frequency, wherein the second frequency is at least about 20 kHz and higher than the first frequency;

measuring a first impedance associated with the first pulse and a second impedance associated with the second pulse; and

determining a hematocrit value based on the first and second impedance measurements.

2. The method of claim 1, wherein the first frequency is greater than at least one of 10 kHz, 50 kHz, 100 kHz, and 1 MHz.

3. The method of claim 1, wherein the second frequency is higher than the first frequency by a multiple of at least one of 2, 5, 10, 20, 50, and 100.

4. The method of claim 1, wherein impedance includes at least one of a resistive component, a reactive component, and a phase angle.

5. The method of claim 1, further comprising:

determining a concentration of an analyte within the sample fluid based in part on the hematocrit value.

6. The method of claim 5, wherein the analyte is glucose.

7. The method of claim 6, wherein the sample fluid includes an enzyme of at least one of glucose oxidase and glucose dehydrogenase and a mediator of at least one of potassium ferricyanide and hexaammineruthenium chloride.

8. The method of claim 1, further comprising:

determining a calibration curve based on one or more hematocrit values.

9. The method of claim 1, wherein the first pulse is applied following the application of the second pulse.

10. A system for determining a hematocrit value of a sample fluid, comprising:

a set of electrodes configured to apply an excitation pulse to the sample fluid;

a processor configured to;

measure a first impedance associated with a first pulse, wherein the first pulse is applied to a sample fluid and the first pulse has a first frequency;

measure a second impedance associated with a second pulse, wherein the second pulse is applied to the sample fluid, and has a second frequency that is at least about 20 kHz and higher than the first frequency; and

determine a hematocrit value based on the first and second impedance measurements.

11. The system of claim 10, wherein the first frequency is greater than at least one of 10 kHz, 50 kHz, 100 kHz, and 1 MHz.

12. The system of claim 10, wherein the second frequency is higher than the first frequency by a multiple of at least one of 2, 5, 10, 20, 50, and 100.

13. The system of claim 10, wherein impedance includes at least one of a resistive component, a reactive component, and a phase angle.

14. The system of claim 10, wherein the processor is further configured to determine a concentration of an analyte within the sample fluid based in part on the hematocrit value.

15. The system of claim 14, wherein the analyte is glucose.

16. The system of claim 15, wherein the sample fluid includes an enzyme of at least one of glucose oxidase and glucose dehydrogenase and a mediator of at least one of potassium ferricyanide and hexaammineruthenium chloride.

17. The system of claim 10, wherein the processor is further configured to determine a calibration curve based on one or more hematocrit values.

18. The system of claim 10, further including a display configured to show the hematocrit value.

19. The system of claim 10, wherein the processor is further configured to apply the first pulse following application of the second pulse.

20. A computer readable media, wherein the media comprises a plurality of instructions configured to direct a processor to:

measure a first impedance associated with a first pulse, wherein the first pulse is applied to a sample fluid and the first pulse has a first frequency;

measure a second impedance associated with a second pulse, wherein the second pulse is applied to the sample fluid, and has a second frequency that is at least about 20 kHz and higher than the first frequency; and

determine a hematocrit value based on the first and second impedance measurements.

21. The computer readable media of claim 20, wherein the first frequency is greater than at least one of 10 kHz, 50 kHz, 100 kHz, and 1 MHz.

22. The computer readable media of claim 20, wherein the second frequency is higher than the first frequency by a multiple of at least one of 2, 5, 10, 20, 50, and 100.

23. The computer readable media of claim 20, wherein impedance includes at least one of a resistive component, a reactive component, and a phase angle.

24. The computer readable media of claim 20, wherein the instructions further direct the processor to determine a concentration of an analyte within the sample fluid based in part on the hematocrit value.

25. The computer readable media of claim 24, wherein the analyte is glucose.

26. The computer readable media of claim 25, wherein the sample fluid includes an enzyme of at least one of glucose oxidase and glucose dehydrogenase and a mediator of at least one of potassium ferricyanide and hexaammineruthenium chloride.

27. The computer readable media of claim 20, wherein the instructions further direct the processor to determine a calibration curve based on one or more hematocrit values.

28. The computer readable media of claim 20, wherein the instructions further direct the processor to output a signal representing the hematocrit value to a display.

29. The computer readable media of claim 20, wherein the instructions further direct the processor to apply the first pulse following application of the second pulse.

30. A test strip for determining a hematocrit value and a glucose value of a blood sample, comprising:

a sample chamber configured to test a blood sample, wherein the chamber includes an aperture configured to receive the sample;

a first set of electrodes configured to apply a first excitation to determine a hematocrit value of the sample, wherein the first set of electrodes are generally free of reagents;

a second set of electrodes configured to apply a second excitation to determine a glucose value of the sample, wherein at least one of the second set of electrodes is located downstream of at least one of the first set of electrodes;

a reagent layer, wherein the layer substantially covers at least one of the second set of electrodes.

31. The test strip of claim 30, wherein at least one of the first set of electrodes and at least one of the second set of electrodes is the same electrode.

32. The test strip of claim 30, wherein the reagent layer includes an enzyme of at least one of glucose oxidase and glucose dehydrogenase and a mediator of at least one of potassium ferricyanide and hexaammineruthenium chloride.