LABORATORY STUDIES AND DIAGNOSTIC TESTS

In persons with known exposure dates, the estimated median time from initial infection to the development of detectable antibody is 2.4 months; 95% of individuals develop antibody within 6 months of infection. The two antibody tests commonly used to detect HIV are the enzyme immunoassay (EIA) for screening and the Western blot for confirmation. Assays for detection of HIV RNA in plasma (e.g., polymerase chain reaction) are sensitive methods for the detection of HIV infection. However, problems with laboratory contamination, false-positive rates, and increased costs limit their routine use. At present, the false-positive and false-negative rates of HIV RNA detection methods are too high to warrant a broader role for them in either routine screening or in the confirmation of diagnosis of HIV infection.
All persons with exposure to HIV should receive postexposure testing. HIV antibody testing should be performed at baseline and for at least 6 months following exposure (e.g., at 6 weeks, 12 weeks, and 6 months). HIV testing using EIA should be performed on any exposed person who has an illness that is consistent with an acute retroviral syndrome.