if someone gets the elisa test three weeks after possible exposure -- and is, in fact, positive -- could the test still come back negative or would it be indeterminate? Thank You.

The test could come back negative, positive, or indeterminate, based on the person's specific immune response and the time of testing. Much information on HIV testing states that the majority (I know that term is not exact) of people will develop a detectable level of antibodies within three weeks of infection. One source estimates that 90% of individuals will seroconvert (become HIV antibody positive) in about one month.

Since some people may take longer than three weeks, it is generally suggested that people wait a minimum of three months following exposure to get tested. This window period allows for a margin of error and yields a definitive result. Some people prefer to wait six months to get tested, though it is extremely unlikely and rare that someone would take six months or longer to test positive on the antibody tests.

RMK