This chapter provides an introduction to immunoassays, explaining their key characteristics, the importance of antibodies and the common assay formats.

David Wild’s career spans 40 years in diagnostics, medical devices, pharmaceuticals and biotechnology. As a University of London undergraduate, he won the Driver Prize for Biochemistry after discovering an extra electron transfer step in photosynthesis. As leaders of the University Biochemistry Society, he and his girlfriend Cindy (now wife) hosted lectures by Sir Hans Krebs and Roger Ekins. After graduation, he worked first as a molecular biologist at a pharmaceutical company R&D laboratory, then, for 25 years, in immunodiagnostics, managing product development and industrial engineering projects. More recently he managed large medical device R&D and operational projects. He worked for Amersham, Kodak, Johnson and Johnson, Bristol-Myers Squibb and ConvaTec. His Director level positions include Research and Development, Design Engineering, Global Manufacturing, and Strategy. He indulges his passion for immunoassays as Managing Editor of The Immunoassay Handbook and lectures, trains and consults on development, manufacturing and marketing strategies, and how to integrate and execute them.

Immunoassay, sensitivity, specificity, antibodies, antibody-antigen binding, immunometric, competitive, signal generation, tracer, separation, antibody testing, second antibody, enzyme-linked immunosorbent assay (ELISA), conjugate, enzyme, substrate, reagent limited, reagent excess, heterogeneous assays, homogeneous assays, standard curve, calibration, quantitative assays, qualitative assays.