The P24 antigen test is a type of test used for early detection of
HIV infection. It detects the presence of the P24 antigen, a protein that is part of the HIV virus, in a person's blood. This test is generally used in combination with an HIV antibody test to improve the accuracy of early diagnosis during the "window period" when the body has not yet produced enough antibodies to be detected.
The P24 antigen test is most useful within a few weeks after potential exposure to HIV, as the viral load is typically highest during that time. However, it's important to note that the P24 antigen can decrease in concentration over time, and after a certain point, it may not be detectable.