Test strip including integral specimen flow retarding structure

• US 5,755,231 A
• Filed: 05/17/1995
• Issued: 05/26/1998
• Est. Priority Date: 05/17/1995
• Status: Expired due to Fees

• Current Assignee: Plus Bio Incorporated
• Original Assignee: Plus Bio Incorporated
• Inventors: Krantz, Gary, Zeng, Joanne, Zipp, Adam, Chen, Shuenn-Tzong
• Primary Examiner(s): Buiz, Michael
• Assistant Examiner(s): RASCHE, PATRICK WILLIAM
• Application Number:
  US08/442,672
• Time in Patent Office: 1,105 Days
• Field of Search: 128/771, 128/760, 422/56, 422/57, 435/11, 435/14, 436/95, 436/169, 436/170
• US Class Current: 600/368
• CPC Class Codes: G01N 33/525 Multi-layer analytical elements

Abstract

A test strip includes a first layer and an overlying differential flow-retarding layer that reduces the fraction of a component of a liquid specimen percolated therethrough. An inert backing, preferably having an aperture therethrough, overlies the flow-retarding layer. For the testing of a blood specimen, the flow-retarding layer is formed of glass fibers that reduce the fraction of red blood cells in the percolate, leaving primarily, but not entirely, plasma in the percolate. The first layer includes chemicals that react with a component of the plasma such as glucose in a measurable reaction, preferably a visually measurable reaction. In using this test strip, the blood specimen is placed into the aperture of the backing and permitted to percolate through the flow-retarding layer such that a fraction of the red blood cells is removed from the percolate. The chemicals in the first layer react with the glucose in the plasma to produce a change that is visually measurable from the bottom side of the active layer with reduced visual interference from the red color of whole blood on the bottom side of the reaction layer.

Claims

1. A test strip, comprising:

a first layer comprising a first porous substrate having a first-layer chemical system impregnated therein, the first-layer chemical system comprising an indicator reagent, wherein the indicator reagent comprises a mixture selected from the group consisting of (1) a mixture of 4-aminoantipyrine and N-ethyl-N-sulfohydroxypropyl-m-toluidine, sodium salt, (2) a mixture of 4-aminoantipyrine and N-ethyl-N-2 Sulfo ethyl m-Toluidine, and (3) a mixture of 3-Methyl-2-benzothiazolinone hydrazone hydrochloride hydrate and N-ethyl-N-sulfohydroxypropyl-m-toluidine, sodium salt; and

a flow-retarding layer comprising a differential flow-retarding material having a percolation rate for blood plasma faster than a percolation rate for red blood cells, the flow-retarding layer overlying the first layer and permitting from about 10 percent to about 90 percent by volume of the red cells to pass therethrough in a period of 45 seconds.

2. The test strip of claim 1, further including

an inert backing overlying the flow-retarding layer, the backing having an aperture therethrough to the flow-retarding layer.

3. The test strip of claim 1, wherein the first-layer chemical system further comprises a reactive reagent.

4. The test strip of claim 3, wherein the reactive reagent is selected from the group consisting of (1) a mixture of glucose oxidase and peroxidase, and (2) a mixture of cholesterol esterase, cholesterol oxidase, and peroxidase.

5. The test strip of claim 1, wherein the first porous substrate comprises a nylon membrane.

6. The test strip of claim 1, wherein the differential flow-retarding material comprises a layer of glass fibers.

7. The test strip of claim 1, wherein the differential flow-retarding material comprises a layer of a material selected from the group consisting of glass fibers and polyester fibers.

8. The test strip of claim 1, further including

a second layer disposed between the first layer and the flow-retarding layer, the second layer comprising a second porous substrate having a second-layer chemical system impregnated therein, the second-layer chemical system comprising a reactive reagent.

9. The test strip of claim 1, wherein the flow-retarding layer comprises

a flow-retarding layer glass fiber paper having a thickness of from about 100 micrometers to about 240 micrometers, a basis weight of from about 20 to about 45 grams per square meter, and a mean pore size of from about 7 to about 9 micrometers.

10. A test strip, comprising:

a first layer comprising a first porous substrate having a first-layer chemical system impregnated therein, the first-layer chemical system comprising

an indicator reagent selected from the group consisting of (1) a mixture of 4-aminoantipyrine and N-ethyl-N-sulfohydroxypropyl-m-toluidine, sodium salt, (2) a mixture of 4-aminoantipyrine and N-ethyl-N-2 Sulfo ethyl m-Toluidine, and (3) a mixture of 3-Methyl-2-benzothiazolinone hydrazone hydrochloride hydrate and N-ethyl-N-sulfohydroxypropyl-m-toluidine, sodium salt, and

a reactive reagent is selected from the group consisting of (1) a mixture of glucose oxidase and peroxidase, and (2) a mixture of cholesterol esterase, cholesterol oxidase, and peroxidase;

a flow-retarding layer comprising a differential flow-retarding material having a permeation rate for blood plasma faster than a permeation rate for red blood cells, the flow-retarding material comprising a glass fiber paper having a thickness of from about 100 micrometers to about 240 micrometers, a basis weight of from about 20 to about 45 grams per square meter, and a mean pore size of from about 7 to about 9 micrometers; and

an inert backing overlying the flow-retarding layer, the backing having an aperture therethrough to the flow-retarding layer.