p24 testing may be used to detect early HIV infection and to screen donated blood for HIV. Since p24 levels rise and fall with HIV levels, the test may also be used to monitor anti-HIV therapy and to evaluate disease progression. The advantages of the p24 test are that it can detect HIV infection days earlier, before antibodies develop, and that it is a quantitative test that tells the intensity of HIV expression in the body, which is a measure of how fast the disease is progressing.

A p24 test may be ordered if you have been recently exposed to HIV and wish to know your HIV status. It may also be ordered if you are donating blood or if you already have HIV and your doctor wants to monitor your response to therapy or to determine if HIV is progressing into AIDS.

A positive result means that you are infected with HIV: the more p24 protein, the higher the amount of HIV in your blood.

The p24 test is one of the earlier tests developed to detect HIV infection. Because p24 is only detectable during a short window of time, its utility is limited. However, this test can still be used when other tests are unavailable.