Early Detection vs. Reliability

The HIV p24 antigen test is proof that not all HIV tests are created equally. This HIV test is valuable for early detection, however there are several shortcomings to this method of testing.

The HIV p24 antigen test is an early detection HIV test that can diagnose the virus as early as one week after exposure. This HIV test measures the level of p24 antigens which are excessively produces shortly after infection. Compared to a standard antibody test which takes three months to produce its most accurate results, the HIV p24 antigen test is a quick alternative.

However, p24 antigens are only detectable until antibodies are produced. In some people, antibodies can develop as early as two weeks. Since there is only a small window of opportunity to detect p24 antigens, this is not an effective HIV test. The HIV p24 antigen test has been largely replaced by the HIV PCR test for early detection.

The technology utilized with the HIV p24 antigen test is now a part of fourth generation HIV tests. These advanced test combine p24 antigen testing and standard antibody testing to reduce the diagnostic window period for highly accurate, early detection HIV testing. Although FDA approved in June 2010, fourth generation HIV tests are not yet widely available.