The HIV test is frequently performed using the ELISA (Enzyme-Linked Immunosorbent Assay) method. This test detects the reaction between an antigen (e.g., a specific protein of a microorganism) and an antibody (a protein-based molecule) produced by the body in response to this antigen. The ELISA method utilizes an enzyme to make this reaction visible, thereby allowing for the detection of infectious agents or the antibodies formed against them, enabling the diagnosis of diseases.