In the reverse syphilis screening algorithm (EIA/CLIA first, then VDRL), a specimen tests reactive on treponemal EIA but non-reactive on VDRL. The recommended next step is:

• A Treat for syphilis empirically — single reactive treponemal test is definitive
• B Repeat VDRL in 3 months — early seroconversion explains the discordance
• C Perform a different treponemal test (TPHA/TP-PA) to resolve discordance ✓
• D Discard as false-positive EIA — VDRL is the gold standard

Explanation

In the reverse (EIA-first) algorithm, a reactive treponemal EIA with a non-reactive VDRL creates a discordant result. The CDC recommends reflex testing with a second treponemal test such as TP-PA (Treponema pallidum particle agglutination) to resolve the discordance. If TP-PA is reactive, the result suggests true syphilis (possibly remote/treated or very early); if non-reactive, it is likely a false-positive EIA. Clinical history (prior syphilis treatment, risk factors) is integrated with results. Empirical treatment without additional testing may lead to unnecessary treatment in false-positive cases.

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

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Written and medically reviewed by the StethoPrep medical team.