A 28-year-old woman presents with secondary syphilis — diffuse maculopapular rash involving palms and soles. RPR titre is 1:64. Which further test must be performed to confirm the diagnosis?

• A Repeat RPR in 4 weeks
• B Treponema pallidum particle agglutination assay (TPPA) or FTA-ABS ✓
• C Dark field microscopy of skin scrapings
• D VDRL on CSF

Explanation

RPR and VDRL are non-treponemal tests that detect reagin antibodies (anti-cardiolipin); they are reactive in syphilis but can give biological false positives in SLE, pregnancy, malaria, and other conditions. A reactive non-treponemal test must always be confirmed by a specific treponemal test — TPPA (Treponema pallidum particle agglutination) or FTA-ABS (fluorescent treponemal antibody absorption) — which detect anti-treponemal antibodies and remain positive lifelong post-infection. Dark-field microscopy is used for primary syphilis chancre exudate. CSF VDRL is reserved for suspected neurosyphilis.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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