ABSTRACT
This chapter provides a detailed and practical introduction to immunoassays. It examines the comprehensive guides to different immunoassay formats ranging from direct to competitive are provided, and subsequently, important signalling systems, including colourimetric and fluorescence-based approaches. A homogenous immunoassay does not require the physical separation of the antibody bound to the analyte from free analyte. Immunoassay methods can be further subdivided into ‘immunometric’ and ‘competitive’ immunoassays. Immunometric immunoassays are commonly used for the detection of molecules such as proteins and viruses, as these entities have the capacity to facilitate the binding of two or more antibodies. A direct antibody immunoassay involves coating analyte either passively or actively onto a solid surface. Indirect immunoassays may be used to detect antibodies in a sample that bind to a particular antigen. Competitive immunoassays are commonly used to measure the presence and concentration of small molecules such as drugs, hormones and toxins.
