immunodiagnostics

Immunodiagnostics refers to diagnostic methods that detect specific components of the immune response, such as antigens, antibodies, or immune complexes, using antigen–antibody interactions. Many assays rely on labeled antibodies or antigens and generate detectable signals through colorimetric, fluorescent, luminescent, or qualitative readouts.

Common methods include enzyme-linked immunosorbent assay (ELISA), which measures antigen or antibody presence in a liquid sample; Western blot, used to confirm protein-specific antibodies; immunofluorescence and immunohistochemistry, which localize antigens in cells or tissue sections; and rapid immunoassays or lateral flow tests, used at or near the point of care for quick results. Other approaches include nephelometry and flow immunoassays.

Applications span infectious diseases (detection of pathogens or host antibodies), autoimmune and allergic disorders, cancer markers, and pregnancy testing based on hormones such as hCG. Sample types include serum, plasma, whole blood, urine, and tissue specimens.

Performance characteristics include sensitivity, specificity, and predictive values, influenced by timing of exposure, cross-reactivity, and pre-analytical factors. While immunodiagnostics enable rapid screening and high-throughput testing, positive results often require confirmation by molecular methods or additional serology, particularly when window periods or low antigen/antibody levels are involved.

Quality control, standardization, and regulatory oversight help ensure accuracy and comparability of tests across laboratories and settings.