Abstract: A test card incorporates a colorimetric indicator test to determine the presence of a minute amount of a specific substance in a liquid medium. The test card includes top and bottom sheets adhesively secured to an intermediate frame member which, together with the top and bottom sheets, defines a filter chamber having a flat filter therein which incorporates a test portion. The test portion of the filter has a binding substrate to which antibodies of the specific substance have been bound. This binding substrate is in communication with a test port. In the method of the invention a substance to be tested is administered through the test port and contains an unknown amount of antigen. After the sample is administered an aqueous solution of enzyme labelled antigen is administered and, subsequently, a liquid substrate is added to cause a color change in the filter below the test portion inversely proportional to the amount of antigen contained in the sample administered at the test port.

Abstract: A stabilized radioimmunoassay product consisting of an antibody protein-bound to the cell wall of a selected bacterium whereby the antibody is irreversibly bound to the protein and remains specific for the antigen against which it was developed. The radioimmunoassay product is also characterized by the fact that the resultant complete product includes a phase of serum protein treatment to isolate the protein sites or other sites of nonspecific reactivity with the labelled antigen such that the non-specific binding of labelled antigen is significantly reduced. Also within the contemplation of the invention is the method of manufacturing the radioimmunoassay product which includes the initial phase of protein binding of the antibody to the selected bacterium and the subsequent serum treatment to isolate previously unutilized protein sites such that when said sites are subsequently exposed to labelled antigen it will be rejected.