ELISA (Enzyme-Linked Immunosorbent Assay) is a laboratory-based test used in the diagnosis of various diseases. This method relies on detecting the specific reaction between an antigen (a protein specific to a microorganism) and an antibody (a protein-based molecule) produced by the body against it. An enzyme is utilized to visualize the test results. This allows for the sensitive detection of infectious agents themselves or the antibodies produced by the body against them.