ELISA is an immunoassay (IA). Basis: immobilization of antigens or antibodies and enzymatic labeling of antigens or antibodies. After the substrate of the enzymatic reaction is added, the substrate is catalyzed by the enzyme to become a colored product, and the amount of the product is directly related to the amount of the test substance in the sample, thereby performing qualitative or quantitative analysis.

        This solid phase enzyme immunoassay was originally called Enzyme Linked ImmunoSorbent Assay ( ELISA) when it was first established in 1971.