A patient with secondary syphilis (maculopapular rash including palms and soles, painless mucosal patches) has a positive RPR titre 1:64. A confirmatory test is performed. Which statement about FTA-ABS is correct?

• A FTA-ABS becomes non-reactive after successful treatment, making it useful for monitoring therapeutic response
• B FTA-ABS is a treponemal test that detects antibodies to Treponema pallidum antigens; it remains reactive for life in most treated patients ('serofast') and cannot be used to monitor treatment ✓
• C FTA-ABS is a non-treponemal test like RPR and VDRL
• D FTA-ABS becomes reactive only in tertiary syphilis

Explanation

FTA-ABS (fluorescent treponemal antibody absorbed) is a specific treponemal test that remains reactive (serofast) for life in most treated individuals and cannot be used to monitor treatment response; the non-treponemal tests (RPR, VDRL) whose titres correlate with disease activity are used for treatment monitoring. A fourfold fall in RPR/VDRL titre after treatment indicates an adequate response. FTA-ABS becomes reactive in primary syphilis (before non-treponemal tests) and remains so throughout all stages.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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