Enzyme-linked Immunosorbent Assay (ELISA) is a biomolecular technique that utilizes the specificity of an antibody, as well as the sensitivity of enzyme assays, to detect and quantify molecules such as hormones, peptides, antibodies, and proteins.

ELISA (enzyme-linked immunosorbent assay) is a method used to quantitatively detect an antigen within a sample. An antigen is a toxin or other foreign substance, for example, a flu virus or environmental contaminant, that causes the vertebrate immune system to mount a defensive response. The range of potential antigens is vast, so ELISAs are used in many areas of research and testing to detect and quantify antigens in a wide variety of sample types. Cell lysates, blood samples, food items, and more can be analyzed for specific substances of interest using ELISAs.

There are three common variations of ELISAs: double antibody sandwich ELISA, indirect ELISA, and competitive ELISA, giving rise to a wide variety of applications – including clinical, forensic, and food research.