Test device and method for colored particle immunoassay

Abstract

Disclosed is a test cell and a method for detection of a preselected ligand in a liquid sample such as a body fluid. The test cell includes an elongate outer casing which houses an interior permeable material capable of transporting an aqueous solution and defining a sample inlet, a test volume, and a reservoir volume. The reservoir volume is disposed in a section of the test cell spaced apart from the inlet and is filled with sorbent material. The reservoir acts to receive liquid transported along a flow path defined by the permeable material and extending from the inlet and through the test volume. In the test volume is a test site which includes a first protein having a binding site specific to a first epitope of the ligand immobilized in fluid communication with the flow path. The test site can be observed through a window of the casing.

Description

BACKGROUND OF THE INVENTION [0001] This invention relates to assays for ligands, e.g., antigens, in a liquid sample such as a body fluid. More particularly, the invention relates to a method and apparatus for the detection of a ligand in a body fluid such as urine using a conjugate comprising colored particles and a novel flow-through test cell. [0002] Many types of ligand-receptor assays have been used to detect the presence of various substances, often generally called ligands, in body fluids such as urine. These assays involve antigen antibody reactions, synthetic conjugates comprising radioactive, enzymatic, fluorescent, or visually observable metal sol tags, and specially designed reactor chambers. In all these assays, there is a receptor, e.g., an antibody, which is specific for the selected ligand or antigen, and a means for detecting the presence, and often the amount, of the ligand-receptor reaction product. Most current tests are designed to make a quantitative determinati...

AI Technical Summary

Benefits of technology

[0008] In a preferred embodiment, the flow path is restricted or narrowed in the test area, thereby channeling and concentrating fluid-flow into contact with the test site. It is also preferred that the test cell include a solution filtering means disposed in the flow path between the sample inlet and the test site. The filtration means can comprise a separate, conventional filter element disposed within the casing of the test cell in fluid communication with the permeable material defining the flow path, but preferably is defined simply by a portion of the permeable material itself. The provision of such a filtration means in the test cell has the effect of removing by entrapment from impure samples, such as urine samples, a portion of the particulates and nonspecific interfering factors which sometimes cause false positive readings.

[0017] The use of the colored particle detection system in combination with the filtration means, the concentrating effect of flow of the sample, and the ease of comparison between the colors of the test and control sites, together enable construction of a family of extremely sensitive assay systems which minimize false positives and can be used effectively by untrained persons.

Problems solved by technology

False positives can also be troublesome, particularly with agglutination and other rapid detection methods such as dipstick and color change tests.

These techniques have not solved all of the problems encountered in these rapid detection methods.

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