serologies

Serology, often encountered in plural as serologies, refers to the study of serum to detect antibodies or antigens and to characterize immune responses. In clinical medicine, serology encompasses laboratory tests that identify antibodies to pathogens or antigens in patient serum, often to diagnose infections, assess immune status, or monitor responses to vaccination. The field relies on immunoassays that detect either binding antibodies or the presence of specific antigens. Common methods include enzyme-linked immunosorbent assay (ELISA), indirect immunofluorescence assays, Western blot, rapid diagnostic tests, and various agglutination or precipitation techniques. Tests may be qualitative (positive/negative) or quantitative, reporting a titer or antibody concentration.

Applications include detection of infectious diseases such as HIV, hepatitis B and C, syphilis, dengue, and many others; assessment of immunity after vaccination (antibody titers); evaluation of autoimmune serology (presence of autoantibodies such as antinuclear antibodies); and screening of blood products to ensure safety. Serology can also measure antibody avidity or neutralizing capacity in research and vaccine studies.

Interpretation requires consideration of timing relative to exposure (the window period), clinical context, and test characteristics. False positives may arise from cross-reactivity with related antigens; false negatives can occur early in infection or in immunocompromised individuals. IgM and IgG patterns help suggest acute versus past infection, but results are not definitive without clinical correlation and, when needed, supplemental testing.

Serology is distinct from other immunoassays that detect current infection by nucleic acids or antigens directly. In research settings, serology supports seroprevalence studies and evaluation of immune responses.