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Syphilis Treatment Response Monitoring — SCE Infectious Diseases MCQ

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ModerateSTIsSyphilis Treatment Response MonitoringSCE Infectious Diseases

A 30-year-old woman with a recent diagnosis of secondary syphilis (RPR 1:128) is treated with Benzathine Penicillin G 2.4 MU IM. She returns for follow-up. At what timepoint is treatment response assessed, and what defines an adequate serological response?

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Correct answer: A — RPR should decline by ≥4-fold (≥2 dilutions) within 6–12 months of treatment — e.g. from 1:128 to ≤1:32

Adequate serological response to syphilis treatment is defined as a ≥4-fold decline (2 dilution steps) in non-treponemal titre (RPR/VDRL) within 6–12 months for early syphilis (6 months) or 12–24 months for late syphilis. For example, RPR 1:128 should decline to ≤1:32 by 6–12 months. Failure to achieve this decline is termed 'serological failure' and should prompt: assessment for neurosyphilis (LP), HIV testing, and consideration of retreatment. Treponemal tests (TPHA) remain positive for life and are not used for monitoring response.

Reference: BASHH 2019 – Syphilis; CDC 2021 – STI treatment