ELISA (Enzyme-Linked ImmunoSorbent Assay) is an immunoassay technique in which an immobilized antigen is detected by an antibody linked to an enzyme capable of generating a detectable reaction. Its use is very common in many laboratories to determine whether a particular antibody is present in the blood sample of a patient. To identify the antigens, molecules are used with two coupled components: an antibody (that binds specifically to the antigen) and an enzyme (which is activated and draws antigen binding).