A decade of development in immunoassay methodology.

Immunoassays are now very widely used in the clinical laboratory, either because no other type of assay system is feasible or because they are often the most effective and suitable of the possible analytical methods. The last decade has seen the development and refinement of many new immunoassay reagents and systems. The major trend has been away from liquid-phase assays involving radioisotopic labels, towards fast homogeneous or solid-phase assays capable of operation anywhere; and towards precise and reliable nonisotopic, automated or semi-automated laboratory assays, often with detection limits measured in pico- or attomoles. The use of monoclonal antibodies is now widespread, and the methodologies of labels and of solid-phase components are much more sophisticated. New assay formulations, novel homogeneous systems, immunosensors, free-analyte assays, the importance of thorough validation and of interfering substances, and future trends are discussed.