ELISA

Enzyme-Linked ImmunoSorbent Assay (ELISA Assay) is a biochemistry technique which is used to determine if a particular protein is present in a protein sample and to quantify how much of the protein is present. ELISA is also used in immunology to detect the presence antibodies or antigens in a given sample.

The ELISA assay utilizes two antibodies: one antibody is specific to the antigen of interest (i.e your protein of interest); and the 2nd antibody is coupled to an enzyme. The second antibody gives the Elisa assay its "Enzyme-linked" name or the EL of ELISA. This secondary antibody catalyzes chromogenic or fluorogenic changes in the presence of a chromgenic or fluorogenic substrate respectively.

Generally there are 5 types of ELISA:

1. Direct ELISA
2. Indirect ELISA
3. Sandwich ELISA
4. Competitive ELISA
5. Multiplex ELISA

ELISA is used to identify the presence of an antigen, such as a disease-related agent, from a sample of body fluid. This is usually the first test used to detect infection with HIV. If antibodies to HIV are present (positive), the test is usually repeated to confirm the diagnosis. If ELISA is negative, other tests are not usually needed.