Enzyme-linked immunosorbent assay (ELISA) is a technique used to detect the presence of specific antibodies or antigens in a sample by using reactions between an enzyme and a substrate to produce a noticeable signal such as a change of color. The development of the enzyme-linked immunosorbent assay (ELISA) was preceded by the radioimmunoassay (RIA), an immunoassay technique that used radioactive antigens and antibodies as a reporter label in the 1960s by Solomon Berson and Rosalyn Yalow (Lequin, 2005 ). However, the use of radioactivity has raised safety concerns, hazardous waste, and the need for expensive laboratories and equipment. This led to the idea of ​​tagging antigens and antibodies with enzymes. According to Lequin (2005), Stratis Avrameas and GB Pierce, each with their respective research groups, have independently developed successful processes for linking antigens/antibodies with enzymes such as alkaline phosphatase (AP) and glucose oxidase to be detected by immunofluorescence. Around 1966, L. Wide and others discovered immunosorbent techniques for attaching antibodies with cellulose beads or Sephadex so that the antibodies could not become soluble. This is done by attaching antigens or antibodies to the surface of a container. In 1971, the Swedish research team led by Peter Pelmann and Eva Engvell at Stockholm University invented the ELISA technique by quantitatively measuring the antibodies, immunoglobulin G (IgG), of rabbits and using alkaline phosphatase as a reporter label. 'enzyme (Lequin, 2005). Boster (2013) briefly outlines the use of hybridomas (monoclonal antibodies) by Georges Kohler and Cesar Milstein in 1975. These hybridomas are immortalized cells generated by the fusion of B lymphocytes with myeloma cells...... middle of paper ... ...005) stated that the basic principle of the technique uses competition between a prepared conjugated form of the antigen and the sample for specific antibody binding sites on the plate. The enzyme-labeled conjugate and sample are mixed and added to the wells to compete for binding with specific antibodies. The conjugate can be differentiated from the sample by adding the appropriate substrate to induce the color change. The competitive ELISA differs from the sandwich or indirect ELISA because of this competition and the way the results are interpreted. In a competitive assay, a weaker colored signal represents a higher concentration of the original antigen as the sample is able to outcompete the prepared conjugate. A low sample concentration will result in greater color development as more of the conjugate binds to the antibody.