Which of the following is not a common HIV viral marker tested in standard screening?

• A. HIV-1 p24 antigen
• B. Anti-HIV-1
• C. Anti-HIV-2
• D. Anti-HTLV-I/II

Answer: (A)

In HIV screening, the markers most consistently targeted are the antibodies to HIV-1 (and often HIV-2) because serology looking for these antibodies has been the cornerstone of screening for many years. The p24 antigen is a viral protein that can indicate infection earlier than antibodies, which is why it is included in newer 4th-generation tests that combine antigen and antibody detection. However, not all standard screening programs rely on p24 antigen as a routine marker; its use depends on the assay and the lab’s protocol. That variability means it isn’t as universally present as the antibody markers, making it the marker not commonly tested in all standard screening panels. Anti-HIV-1 and anti-HIV-2 antibodies are the traditional, widely used targets in screening, and while HTLV testing can be relevant in some contexts, it is not a standard HIV screening marker.