A 34-year-old woman being evaluated for recurrent miscarriage is found to have an RPR reactive at a titre of 1:2. Her TPPA is non-reactive and she is asymptomatic. Repeat testing after 12 weeks shows the same low-titre reactive RPR with persistently non-reactive TPPA. Which condition best explains this serological pattern?

• A Systemic lupus erythematosus ✓
• B Secondary syphilis
• C Late latent syphilis
• D Yaws

Explanation

B persistent low-titre reactive non-treponemal test with repeatedly negative treponemal tests defines a biological false positive, classically caused by antiphospholipid antibodies in systemic lupus erythematosus and antiphospholipid syndrome. Secondary syphilis, late latent syphilis and yaws are all true treponemal infections and would give a reactive TPPA or FTA-ABS, so they are excluded by the negative treponemal test. Chronic false positivity is defined as persistence beyond six months.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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