hivtests

HIV tests are medical tests designed to determine whether a person has been infected with the human immunodeficiency virus (HIV). They detect either antibodies the immune system makes in response to infection, viral antigens, viral RNA, or a combination of these markers. Testing supports diagnosis, connects people to care, and helps prevent transmission.

Tests come in several types. Fourth-generation tests detect both HIV-1/2 antibodies and the p24 antigen and can identify many infections earlier than antibody tests alone. Nucleic acid tests (NAT) detect HIV RNA and are used to diagnose acute infection or resolve discordant results, though they are more expensive and less widely used for routine screening. Antibody-only tests look for antibodies to HIV and are common in rapid tests and some lab assays. Rapid point-of-care tests provide results within minutes, often using blood from a finger prick or oral fluid, while laboratory tests use blood samples processed in a lab.

Window period and accuracy: No test detects HIV immediately after exposure. NAT can detect infection about 10 days to two weeks after exposure; fourth-generation antigen/antibody tests usually detect infection within about 2–6 weeks for most people, with most infections detectable within 3 months. All positive screening results require a follow-up confirmatory test, such as a differentiation assay or a NAT, to confirm HIV infection.

Guidelines and access: People at risk should test at least annually, with more frequent testing (every 3–6 months) for those with ongoing risk. After potential exposure, testing should be done as soon as possible and again 3 months later if the initial result is negative. At-home tests are available in some regions, such as FDA-approved oral-fluid self-tests, but positive results require confirmatory clinical testing.

Viral load testing and care: Once diagnosed, HIV viral load tests monitor response to treatment, while antibody tests confirm infection status.