The confirmatory test commonly used after an initial HIV screen is what?

• A. ELISA
• B. PCR
• C. RT-PCR
• D. HIV Western blot (immunoblot)

Answer: (D)

After an initial HIV screen, you want a test with high specificity to confirm true infection. HIV Western blot (immunoblot) does this by detecting antibodies to several specific HIV proteins (such as p24, gp41, and gp120/160). Because it requires antibodies to multiple viral components, it reduces the chance of a false positive that might occur with the screening test, giving a more definitive result. Historically, a positive pattern of these bands indicates infection, while incomplete or unclear patterns are considered indeterminate and require further testing. In contrast, tests that look for the virus’s genetic material (PCR or RT-PCR) or the screening test itself are not used as the standard confirmatory antibody test after the initial screen.