Syphilis

Clinic A/P, adults, Clinic A/P, Peds, Hospital A/P, Adults, Hospital A/P, Peds

Diagnosis
A presumptive diagnosis of syphilis requires use of two tests: a nontreponemal test (i.e. VDRL] or RPR]) and a treponemal test (i.e., FTA-ABS tests, TP-PA assay, EIAs, chemiluminescence immunoassays, immunoblots, or rapid treponemal assays). The nontreponemal tests (RPR or VDRL) are only screening tests which can have false positives. The confirmation is with the treponemal test.
You need both tests to avoid false negatives (in pts with primary syphilis) or false positives (in pts who don’t have syphilis).

See Screening and Treatment of Syphilis here.

*Good response to treatment is when titters decrease by more than four-fold.
*If you are treating a patient, you should get a titter on the day of treatment and use that as  the titter to follow. Why? The titter may have gone up since the time of diagnosis and you would not know the effect of your treatment.
An I.D. doc I spoke with repeats titters after 2-3 months of initiating treatment and follows it until it decreases by more than four fold.

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A patient comes with an ulcer on her labia, which has been present for a week. You suspect primary syphilis, but a rapid plasma reagin (RPR) test is negative. What should you do next? Answer: Repeat the RPR test in 2 weeks

“A nontreponemal test, such as the rapid plasma reagin (RPR) test or Venereal Disease Research Laboratory (VDRL) test, is the initial step for evaluating a patient with suspected syphilis. These tests become positive within 3 weeks of the appearance of the primary chancre, so they may be negative in patients with an early infection. Darkfield microscopy of material obtained from a swab of the lesion is often useful in this situation, but it requires special equipment and experienced technicians. If there is a strong suspicion of syphilis, a repeat nontreponemal test in 2 weeks is indicated. Patients with a positive nontreponemal test should be tested with a specific treponemal test for confirmation. These tests may lack reactivity in early primary syphilis, however, and are not indicated for use in the initial evaluation. Spinal fluid analysis is used only for the evaluation of tertiary syphilis.” ABFM

Reference

Am Fam Physician 2012;86(5):433-440.

https://www.cdc.gov/std/tg2015/syphilis.htm

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