The HIV chemiluminescence test is an automated chemiluminescent immunoassay that detects HIV antibodies and the p24 antigen. It’s highly sensitive and specific, commonly used for screening blood and clinical samples with rapid, automated readouts. Reactive results require supplemental confirmation (nucleic acid testing or confirmatory serology) because early infection window periods and occasional false positives can occur.

Immunochromatographic (rapid) HIV tests are highly accurate for screening: sensitivity and specificity generally exceed 99% after the window period. However, they can miss very recent infections (the early window of several weeks), so negative results soon after exposure should be repeated or confirmed with lab-based antigen/NAAT testing. Positive rapid results require laboratory confirmation.

Chemiluminescence immunoassays (commonly used 4th‑generation antigen/antibody tests) can detect HIV as early as about 2 weeks after exposure (p24 antigen), are reliably positive for most people by 4–6 weeks, and reach conclusive accuracy by 3 months. If exposure was very recent, repeat testing at 4–6 weeks and again at 3 months is recommended; any reactive result needs confirmatory testing.

Seroconversion in HIV is the period after infection when the immune system produces detectable antibodies, causing an HIV test to turn positive. It typically occurs 2–4 weeks after exposure (up to three months). Many people experience flu-like symptoms — fever, sore throat, rash, swollen lymph nodes — called acute retroviral syndrome. Nucleic acid or antigen tests can detect infection earlier than antibody tests.

Chemiluminescence tests (chemiluminescent immunoassays) detect very small amounts of substances by producing light during a chemical reaction. They’re used in clinical labs to measure hormones (TSH, free T4), infectious disease markers and antibodies (HIV, hepatitis), cardiac markers (troponin), tumor markers, vitamin D, autoimmune antibodies and some drug/toxin screens, offering high sensitivity, specificity and rapid automated processing.

Two common types of HIV testing are: 1) Antigen/antibody (fourth‑generation) lab tests that detect HIV p24 antigen and antibodies, usually reliable from about 2–6 weeks after exposure; and 2) Nucleic acid tests (NAT or RNA/PCR) that detect viral genetic material and can diagnose infection earlier (often 7–14 days), though they are costlier and used for early/high‑risk detection.