If a patient has a reactive HIV screening test but nonreactive anti-HIV-1 and anti-HIV-2 results, which test should be performed on the same sample to detect acute infection?

• A. Repeat testing in 3 months
• B. Western blot on the present sample
• C. HIV nucleic acid amplification test on the present sample
• D. Notify the primary care provider

Answer: (C)

Detecting HIV during the acute phase requires looking for the virus itself, not just the antibodies. When a screening test is reactive but the anti-HIV-1/2 antibodies are nonreactive, it suggests infection in the window period before seroconversion. HIV RNA becomes detectable in blood earlier than antibodies, so performing an HIV nucleic acid amplification test on the same sample will reveal the presence of viral RNA and confirm acute infection. Western blot relies on antibodies, so it would often be negative during this early stage and isn’t useful for diagnosing acute infection. Repeating antibody testing later could confirm infection after seroconversion, but it wouldn’t identify the current acute infection promptly. Notifying the primary care provider is not a diagnostic test.