HIV P24 Antigen

The HIV p24 antigen test is a diagnostic tool used to detect the presence of the p24 protein, a core structural component of the HIV virus. High levels of this antigen are present in the blood during the initial stage of an HIV infection, known as the acute or primary phase, before the body has produced a significant amount of antibodies. Because p24 antigen can be detected as early as 11-14 days after infection, this test is valuable for the early diagnosis of HIV, helping to shorten the "window period"—the time between exposure and when a test can accurately detect the virus. While older, standalone p24 tests existed, the p24 antigen is now most commonly detected as part of a fourth-generation HIV test, which simultaneously checks for both p24 antigen and HIV antibodies, making it the most reliable and widely used screening test for early HIV detection.