immunoassay(redirected from FPIA)
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An assay that quantifies antigen or antibody by immunochemical means. The antigen can be a relatively simple substance such as a drug, or a complex one such as a protein or a virus. See Antibody, Antigen
The reactants are first mixed so that a varying quantity of one (A) is added to a constant amount of the other (B). The formation of an immune (antigen-antibody) complex is measured as a function of the varied reactant (A). The result is represented by a “standard curve” for reactant A. An unknown sample is tested by adding it to reactant B. The extent of the measured change is referred to the standard curve, and thereby is obtained the amount of reactant A which produces a comparable change. The amount is represented as the content of reactant A in the unknown sample. See Immunofluorescence, Immunology, Radioimmunoassay