Immunochemical assays in the clinical laboratory

State-of-the-art immunochemical assays and future directions in this science are reviewed. Immunochemical assays may be categorized as follows: Type I, or single-site noncompetitive immunoassays; type II, two-site noncompetitive immunoassays; type III, homogenous competitive immunoassays; and type IV, nonhomogenous competitive immunoassay. Assay systems use radionuclides, enzymes, fluorescence, chemiluminescence, and particles as reporters in the tests. Radionuclides will continue to decline in importance as other systems are refined. More sensitive reporters and clever multi-analyte systems will continue to be developed.