Conductivity measurement cell

• US 9,689,821 B2
• Filed: 12/24/2009
• Issued: 06/27/2017
• Est. Priority Date: 12/31/2008
• Status: Active Grant

• Current Assignee: SPD Swiss Precision Diagnostics GmbH (Abbott Laboratories)
• Original Assignee: SPD Swiss Precision Diagnostics GmbH (Abbott Laboratories)
• Inventors: Barnard, Jonathan D., Carlisle, Stephen J., Jones, Malcolm R.
• Primary Examiner(s): WHITE, DENNIS MICHAEL
• Application Number:
  US13/142,561
• Publication Number:
  US 20110291670A1
• Time in Patent Office: 2,742 Days
• Field of Search: 422 52, 422 73, 422 8201, 422 8205, 422 8208, 422 8209, 422 8211, 422 99, 422102, 422400, 422401, 422420, 422421, 422422, 422423, 422424, 422425, 422426, 422427, 422428, 422429, 422 681, 422 8206, 422407, 422501, 422502, 422503, 422504, 436164, 436177, 436 43, 436 63, 435 29, 435 4, 435 6, 435 71
• CPC Class Codes: G01N 27/07 Construction of measuring vessels; Electrodes therefor
• CPC Class Codes: G01N 33/493 urine
• CPC Class Codes: H03K 3/0315 Ring oscillators

Abstract

The application relates to a conductivity measurement cell for measuring the concentration of a preselected biomarker or analyte in a body fluid, such as urine. In order to reduce the effect of sample dilution on measured concentration, the measured concentration can be normalized by a dilution factor, which can be determined from electrical conductivity. A test strip and measurement apparatus is disclosed for performing such normalized concentration measurement.

Claims

1. A conductivity measurement system comprising:

a test strip having a body, a sample container, a reference chamber, and a plurality of electrodes; and

a measurement component coupled to the electrodes and configured to obtain a plurality of conductance measurements, wherein;

the sample container and the reference chamber are separated by a coincident membrane, the coincident membrane having two opposed sides, one side in contact with the sample container and the other side in contact with the reference chamber, and

the measurement component is coupled to the sample container, the reference chamber, and the electrodes, and configured to;

based on the plurality of conductance measurements, provide a determination that a temperature of the sample container and a temperature of the reference chamber are substantially the same and,

based on the determination, derive a corrected amount or concentration of an analyte in a sample situated in the sample chamber.

2. A conductivity measurement system according to claim 1 in which the sample container and the reference chamber are arranged so as to maximize the ratio of membrane surface area to sample container volume.

3. A conductivity measurement system according to claim 1, wherein the plurality of electrodes comprises a first electrode and a second electrode, wherein the first and second electrodes are spaced apart and arranged so as to connect electrically in parallel across the reference chamber and the sample container.

4. A conductivity measurement system according to claim 1, wherein the plurality of electrodes comprises a first electrode, a second electrode and a third electrode, the first and second electrodes spaced apart and arranged so that in use they connect across the reference chamber, and the second and third electrodes arranged so that in use they connect across a sample contained in the sample container.

5. A conductivity measurement system according to claim 1 comprising a sample application zone which fluidically connects to the sample container via a capillary channel.

6. A conductivity measurement system according to claim 1 wherein the reference chamber is sealed and contains a reference liquid, gel or solid, or the reference chamber comprises an electrical component.

7. A conductivity measurement system according to claim 6 wherein the reference gel comprises potassium chloride.

8. A conductivity measurement system according to claim 1 further comprising a binding reagent for the analyte of interest.

9. A conductivity measurement system according to claim 1 wherein the electrodes have a chamfered edge in contact with the sample and/or reference, or the electrodes have surface features which increase their contact surface area with the reference and/or sample.

10. A conductivity measurement system according to claim 1 wherein the electrodes are over-molded.

13. The conductivity measurement system according to claim 1, wherein the measurement component is configured to obtain the plurality of conductance measurements, and wherein the plurality of conductance measurements comprises:

a measurement of a first, inherent conductance of the measurement component;

a measurement of a second conductance associated with a reference situated in the reference chamber is connected electrically to the measurement component; and

a measurement of a third conductance associated with the reference and the sample situated in the reference chamber and the sample container, respectively; and

wherein the measurement component provides the determination based on the measurements of the first, second and third conductances.

11. A conductivity measurement system comprising:

a conductivity measurement test strip having a body, a sample container and a reference chamber, the sample container and the reference chamber separated by a coincident membrane, the coincident membrane having two opposed sides, one side in contact with the sample container and the other side in contact with the reference chamber;

a measurement component having a first node and a second node,

wherein the test strip is configured for use with the measurement component for deriving a temperature corrected measure of electrical conductivity of a sample, and wherein the measurement component is configured to provide;

a measurement of a first, inherent conductance of the measurement component;

a measurement of a second conductance when a reference is connected electrically to the measurement component between the first node and the second node;

a measurement of a third conductance when a sample is connected electrically to the measurement component; and

further configured to;

provide a determination that a temperature of the sample container and a temperature of the reference chamber are substantially the same by combining the first, second and third conductance measurements; and

,

based on the determination, derive a corrected amount or concentration of an analyte in the sample.

12. A method, comprising:

measuring a plurality of conductances using a conductivity measurement system comprising;

a test trip having a body, a sample container and a reference chamber, the sample container and the reference chamber separated by a coincident membrane, the coincident membrane having two opposed sides, one side in contact with the sample container and the other side in contact with the reference chamber, and

a measurement component;

based on the plurality of conductance measurements, providing a determination that a temperature of the sample container and a temperature of the reference chamber are substantially the same; and

based on the determination, deriving a corrected amount or concentration of an analyte in the sample.

14. A device for deriving a corrected amount or concentration of an analyte in a sample, comprising:

a conductivity measurement test strip having a body, a sample container, a reference chamber, the sample container and the reference chamber separated by a coincident membrane, the coincident membrane having two opposed sides, one side in contact with the sample container and the other side in contact with the reference chamber; and

a measurement component switchably electrically coupled to the sample container and the reference chamber and configured to measure a plurality of conductances, wherein the plurality of measured conductances are used to provide a determination that a temperature of the sample container and a temperature of the reference chamber are substantially the same, and configured to, based on the determination, derive a corrected amount or concentration of an analyte in the sample.

15. The device according to claim 14, wherein the plurality of measured conductances comprise:

a first, inherent conductance of the measurement component;

a second conductance when a reference in the reference chamber is connected electrically to the measurement component; and

a third conductance when a sample in the sample container is connected electrically to the measurement component, and

wherein the measurement component is configured to derive a temperature corrected measure of conductivity from the first, second and third conductance measurements in order to provide the determination.