AIDS and HIV Infection • Being tested
What the HIV antibody test can tell you
The standard tests to determine whether you are infected with HIV are based on detection of antibodies to HIV in the blood, not of the virus itself.
Different types of antibody tests exist such as the enzyme-linked immunosorbent assay (ELISA) and simple rapid (S/R) tests. In recent years, tests have been developed that detect HIV antibodies in saliva and urine.
The first antibody test a person gets is called a screening test.
HIV screening tests can sometimes give false-positive readings, especially in populations where HIV is not present in high numbers, which is why confirmatory testing is always done on positive screening test results. This confirmation is needed to rule out false-positive screening results.
In regard to the accuracy of the antibody tests:
- It takes, on average, 25 days for an HIV test to show positive after a person becomes infected with HIV. This is a much shorter timeframe than before the introduction of very sensitive tests now used.
- If a person has been infected very recently, the test may show a negative result.
- When saliva and urine are tested, it takes longer for antibodies to become detectable.
- More than 99 percent of infected persons will show positive after three months.