Fluid conducting test strip with transport medium

• US 5,968,836 A
• Filed: 06/22/1995
• Issued: 10/19/1999
• Est. Priority Date: 05/12/1992
• Status: Expired due to Term

• Current Assignee: Lifescan Incorporated (Duv Holding Corporation)
• Original Assignee: Lifescan Incorporated (Duv Holding Corporation)
• Inventors: Matzinger, David P., Zweig, Steven, Yu, Yeung S.
• Primary Examiner(s): ALEXANDER, LYLE
• Application Number:
  US08/493,435
• Time in Patent Office: 1,580 Days
• Field of Search: 422/56-61, 436/169-170, 436/177-178, 435/805, 210/506, 210/926
• US Class Current: 436/169
• CPC Class Codes: G01N 21/8483 Investigating reagent band test-element handling not specific to a test method G01N33/4875; analytical elements specific to chemical analysis of biological material G01N33/52; autometer with reagent band G01N35/04
• CPC Class Codes: G01N 33/525 Multi-layer analytical elements
• CPC Class Codes: Y10T 436/255 including use of a solid sorbent, semipermeable membrane, or liquid extraction

Abstract

A reagent strip is provided for measuring the concentration of an analyte in a liquid test sample, such as glucose or cholesterol in whole blood. The reagent strip includes a testing pad containing a color-forming reagent system specific to the analyte. The testing pad is disposed so that a side with relatively small pores defines a testing surface and an opposite side with relatively larger pores defines a sample-receiving surface. A porous sample transport medium is attached to the sample-receiving surface. A change in coloration caused by the color-forming reagent system at the testing surface is quantitatively related to the concentration of the analyte in the liquid test sample. The reagent strip may optionally include a rigid support member which facilitates evaluation of the change in coloration by mechanical viewing means. Also provided is a method for determining the concentration of an analyte in a liquid test sample.

Claims

1. A reagent strip for measuring the concentration of an analyte in a test sample, suitable for evaluation by the human eye or by mechanical viewing means, consisting essentially of:

a testing pad formed from an anisotropic membrane impregnated with a color-forming reagent system specific to an analyte and having a side with relatively small pores which defines a testing surface and an opposite side with relatively large pores which defines a sample receiving surface; and

a porous sample transport medium attached to the sample receiving surface of the testing pad, said transport medium being capable of accepting a whole blood sample on a sample accepting surface and transporting a detectable portion of the sample to the sample receiving surface.

2. The reagent strip of claim 1 wherein the sample accepting surface of the transport medium is coated with a film containing a hydrophobic polymer.

3. The reagent strip of claim 1 wherein the transport medium is capable of holding about 35 microliters of blood and of passing about 3 microliters of blood to said testing pad.

4. The reagent strip of claim 1 wherein the transport medium has pores which are in the size range of about 20 to about 200 micrometers.

5. The reagent strip of claim 1 wherein the transport medium is composed of polyethylene.

6. The reagent strip of claim 1 wherein the testing pad has pores in the size range of about 5 to about 50 micrometers on the side with relatively large pores decreasing to about 0.1 to about 1.0 micrometer on the side with relatively small pores.

7. The reagent strip of claim 1 wherein the testing pad is composed of polysulfone.

8. The reagent strip of claim 1 wherein an adhesive layer formed along an outer edge of the testing pad is attached to the testing pad and the transport medium.

9. The reagent strip of claim 1 wherein a discontinuous adhesive layer is positioned between and attached to the testing pad and the transport medium.

10. The reagent strip of claim 1 which further comprises a rigid support member defining an aperture therethrough and having a free surface adapted to contact and engage mechanical viewing means.

11. The reagent strip of claim 10 wherein the transport medium includes a region that does not contact the testing pad.

12. A reagent strip for measuring the concentration of an analyte in a test sample suitable for evaluation primarily by mechanical viewing means, consisting essentially of:

a rigid support member defining an aperture therethrough and having a surface adapted to contact and engage viewing means and a portion disposed about the aperture with a predetermined thickness;

a testing pad formed from an anisotropic membrane impregnated with a color-forming reagent system specific to an analyte and having a side with relatively small pores which defines a testing surface and an opposite side with relatively large pores which defines a sample receiving surface, said testing surface being attached to said support member so that the testing surface faces and overlaps the aperture; and

a porous sample transport medium attached to the sample receiving surface of the testing pad, said transport medium being capable of accepting a whole blood sample and transporting a detectable portion of the sample to the sample receiving surface;

whereby the testing surface is maintained at an optimum viewing distance relative to said viewing means when the free surface of the support member engages said viewing means.

13. The reagent strip of claim 12 wherein the portion of the support member disposed about the aperture has a thickness in the range of about 0.002 to about 0.050 of an inch.

14. The reagent strip of claim 12 wherein the transport medium is capable of holding about 35 microliters of blood and of passing about 3 microliters of blood to said testing pad.

15. The reagent strip of claim 12 wherein the transport medium has pores which are in the size range of about 20 to about 200 micrometers.

16. The reagent strip of claim 12 wherein the transport medium is composed of polyethylene.

17. The reagent strip of claim 12 wherein the testing pad has pores in the size range of about 5 to about 50 micrometers on the side with relatively large pores decreasing to about 0.1 to about 1.0 micrometer on the side with relatively small pores.

18. The reagent strip of claim 12 wherein the testing pad is composed of polysulfone.

19. The reagent strip of claim 12 wherein an adhesive layer formed along an outer edge of the testing pad is attached to the testing pad and the transport medium.

20. The reagent strip of claim 12 wherein a discontinuous adhesive layer is positioned between and attached to the testing pad and the transport medium.

21. A method for measuring the concentration of an analyte in a test sample containing solid color bodies which comprises:

providing a reagent strip which consists essentially of a testing pad formed from a porous anisotropic membrane impregnated with a color-forming reagent system specific to an analyte which defines a testing surface and a sample receiving surface, and a porous sample transport medium attached to the sample-receiving surface;

contacting a test sample of a biological fluid which contains the analyte and solid color bodies with the transport medium;

absorbing the test sample into the transport medium, transporting the test sample to the sample receiving surface, and distributing the test sample across the sample-receiving surface;

transporting and filtering the test sample through the testing pad in a direction which exposes the sample to progressively smaller pores, separating at least some of the solid color bodies from the test sample; and

chemically reacting the testing reagent with the analyte to vary coloration of the testing surface INS H1.

22. The method of claim 21 in which the coloration of the testing surface is compared to a calibrated color standard to determine the concentration of the analyte in the test sample.

23. The method of claim 21 which further comprises locating the testing surface a reproducible distance from a viewing means by contacting the viewing means with a rigid support member which has a controlled thickness, defines an aperture, and abuts the testing surface.

24. A reagent strip for measuring the concentration of an analyte in a liquid sample which exhibits an optically visible color change as a function of the concentration of said analyte in said sample, consisting essentially of:

a relatively rigid support member having opposed first and second major surfaces and having an aperture therethrough;

a testing pad overlying said aperture on said first major surface, said testing pad having a sample receiving surface and an opposed testing surface, with said testing surface in face-to-face relationship with said first major surface of said support and with a portion of said testing surface being optically visible through said aperture;

said testing pad formed from a porous anisotropic membrane, said pores decreasing in effective diameter from said sample receiving surface to said testing surface;

said testing pad impregnated with reactants selected to react with said analyte if present in said testing pad to produce a color change visible at said testing surface;

a porous sample transport medium overlying said sample receiving surface of said testing pad and having portions extending beyond the perimeter of said testing pad to overlie, in face-to-face contact, the first surface of said support member;

whereby said liquid sample may be applied to said transport medium, a portion of said sample may be transported to the sample receiving surface of said testing pad and a portion of said sample may be transported through said testing pad, wherein analyte if present will react with said reactants in said testing pad and any resulting color change will be visible on the testing surface through said aperture, and whereby said portion of the transport medium extending beyond the perimeter of the testing pad provides a reservoir for excess liquid sample applied to the transport surface.

25. The test pad of claim 24 wherein the transport medium comprises essentially incompressible material to ameliorate the unintended expulsion of applied liquid sample.

26. The test pad of claim 25 wherein the outer surface of said transport medium is hydrophobic with respect to the remainder of the transport medium.