Your response, "Yes p24 antigen will always be positive prior to seroconversion. But..It will be declining as antibodies develop, and can rarely be gone before the antibody test is positive.". Base on your response, if a person has negative results on the p24 antigen and elisa tests at any given time on the same blood sample will rule out HIV. Isn't that the blood bank is using these tests to screen blood donors? Why people have to wait for the 6 months window to have a conclusive antibody test (elisa)? Is this because the currently elisa test is not sensitive enough to pick the antibody at the early stage of seroconvert? Thanks.

There are competing agencies, regulations and policy in play over this question. Screening by blood banks is different than screening people because of high risk exposure. Blood banks use both tests to screen. That will probably change because they wil probably go to viral load testing soon. The CDC still currently recommends antibody testing for 6 months as the most accurate and economical way to approach diagnosis. Viral load is not approved for diagnosis. To study acute infection, requires 100s of patients. Most of the data we have is anecdotal and thus studies will take time to work out the best screening strategies for acute infection. MH