Which test confirms secondary syphilis?

• A. Lyme titer
• B. C-reactive protein
• C. FTA-ABS
• D. Weil-Felix test

Answer: (C)

A confirmatory test for syphilis in the setting of suspected secondary disease is a test that detects antibodies specifically against Treponema pallidum. FTA-ABS, the fluorescent treponemal antibody absorption test, does just that by identifying T. pallidum–specific antibodies in the patient’s serum. It’s highly specific for syphilis and typically remains positive for life, making it reliable to confirm infection after an initial screen has suggested exposure. In practice, screening tests like non-treponemal assays may be positive in secondary syphilis, but the treponemal test provides the definitive confirmation. Other options don’t fit the diagnosis: a Lyme titer targets Borrelia burgdorferi, C-reactive protein is a nonspecific inflammatory marker, and the Weil-Felix test is used for certain rickettsial infections.