Which test is the only acceptable confirmatory test per FDA?

• A. RPR
• B. ELISA
• C. FTA-ABS
• D. VDRL

Answer: (A)

The key idea here is how syphilis testing is structured: screening tests look for antibodies that can appear in a range of conditions, while confirmatory tests specifically verify true infection with Treponema pallidum.

Non-treponemal tests (like RPR and VDRL) are used for screening because they’re quick and inexpensive and their titers reflect disease activity. However, they’re not specific to syphilis and can yield false positives, so they aren’t used alone to confirm infection.

For confirmation, a treponemal-specific antibody test is used. Among FDA-cleared options, FTA-ABS is the standard confirmatory test because it detects antibodies directed against Treponema pallidum with high specificity. ELISA can also detect treponemal antibodies in some assay formats, but the established confirmatory choice in this context is FTA-ABS.