This chapter reviews the more common and most interesting labelling and signal detection methods, including radioactive, enzyme (colorimetric, fluorometric, chemiluminescent, enhanced chemiluminescent), direct fluorescent, time-resolved fluorescent, direct chemiluminescent, phosphorescent, micro- and nanoparticle, streptavidin/avidin-biotin and protein A. There are sections on amplification strategies, multiple analytes and miniaturization (including microarrays).

Rui Liu, at Chengdu University of Technology in China, pointed out that there have been significant developments using inductively coupled plasma mass spectrometry as a detection method for immunoassays in conjunction with element tagging. Tags (labels) include metal ions, nanoparticles and metal-containing polymers. A variety of formats have been used, including capillary electrophoresis. This methodology lends itself to multiplex assays using MS to distinguish between and quantify multiple labels in the same assay. He and his colleagues have written an excellent review of the subject: Inductively-Coupled Plasma Mass Spectrometry-based Immunoassay: A Review. Mass Spectrometry Reviews 33, 373–393 (2014).

Professor Ian Weeks BSc PhD DSc CChem FRSC FRCPath is presently Professor in Translational Biochemistry at Cardiff University School of Medicine where he is Deputy Director in the Institute of Translation, Innovation, Methodology and Engagement. His interests are in the development of non-invasive tests, based on biochemical methods, for the prediction, diagnosis and prognosis of disease. Advances in molecular signaling technologies now permit the development of highly sensitive and specific tests which can be used in multiplex formats within laboratory environments or as the basis for point-of-care platforms to better inform diagnostic decisions and subsequent interventions. He has over 30 years experience in the research and development of in vitro diagnostic test systems in both academia and industry and in the commercialization of novel diagnostic technologies.

This chapter also contains material by Larry Kricka and David Wild from the third edition of The Immunoassay Handbook.

Signal generation, signal detection, radioimmunoassay, radioactive, isotope, half-life, iodine-125, tritium, scintillation, label, sensitivity, specific activity, chemiluminescence, electrochemiluminescence, enhanced chemiluminescence, enzymeimmunoassay, colorimetric, fluorescence, fluorophore, Stokes’ shift, quantum yield, quantum efficiency, quenching, bridge, alkaline phosphatase, horseradish peroxidase, conjugation, quantum dots, time-resolved fluorescence, bioluminescence, phosphorescence, up-converting phosphor, latex particle, colloidal gold, silver enhancement, gold cluster, magnetic particles, streptavidin, avidin, biotin, protein A, amplification, enzyme amplification, catalyzed reporter deposition, polymerase chain reaction, expression immunoassay, confocal microscopy, microarray, matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy, atomic force microscopy, mosaic-format immunoassay.