serologii

Serology is the study of serum and immune responses, focusing on antigen–antibody interactions to detect exposure to pathogens, diagnose diseases, and assess immune status. It encompasses laboratory techniques that identify antibodies in patient serum or antigens, and can quantify antibody levels (titers) or detect present antigens.

History: Serology emerged in the late 19th and early 20th centuries with development of antibody-based tests. Key milestones include discovery of antibodies, ABO blood grouping, and the development of precipitation, agglutination, and immunoassays such as ELISA in the latter half of the 20th century.

Principles and methods: Most serologic tests rely on specific binding between antibodies and antigens, producing detectable signals. Common methods include agglutination tests, precipitation assays, immunofluorescence, Western blot, enzyme-linked immunosorbent assay (ELISA), chemiluminescent assays, and rapid tests such as lateral flow immunoassays. Modern assays may be qualitative or quantitative.

Applications: In medicine, serology aids diagnosis of infections (HIV, hepatitis B and C, syphilis, dengue, SARS-CoV-2), assessment of prior exposure, and evaluation of vaccine responses. It is essential in transfusion medicine for blood typing and antibody screening, in autoimmune disease testing (autoantibodies), and in epidemiological seroprevalence studies.

Specimens and interpretation: Serum is the primary specimen, though plasma and other fluids may be used. Interpretation depends on test characteristics; sensitivity, specificity, and prevalence influence predictive values. Serology may detect antibodies (past or present infection) or antigens (active infection).

Limitations: Antibody presence does not always indicate current infection; cross-reactivity can cause false positives; vaccination can yield seropositivity; a window period may delay detection.

Quality and standards: Serologic testing relies on standardized reagents, controls, and validated assays to ensure accuracy. Results are reported with reference ranges, cutoffs, and confidence measures.