Rapid Plasma Reagin Titer Variation in the 2 Weeks After Syphilis Therapy

Abstract

Background Serologic tests for syphilis (STS) results at time of diagnosis are the basis for evaluating response to syphilis therapy. Following treatment, however, STS titers may continue to increase for several weeks. We evaluated RPR titer variation over the 14 days following therapy using data from a recent large, prospective RCT. Methods Prospectively enrolled participants in North America and Madagascar with primary, secondary or early latent syphilis were randomly assigned to penicillin, doxycycline (in the case of penicillin allergy) or azithromycin treatment. Blood for RPR analysis was drawn at days 0, 7, and 14 post-treatment. All RPR titers were determined simultaneously at a central laboratory. Results 470 patients had data available for at least 2 of 3 RPR measurements. Overall, 20% of patients showed a titer increase of at least one dilution in the 14 days following therapy. The greatest proportion of titer increases following therapy was seen in patients with primary syphilis. Comparing outcome of therapy using the initial (day 0) RPR titer vs. the maximal RPR titer (over 14 days), resulted in outcome reclassification in 2.98% of participants. Conclusions Despite the fact that about 20% of early syphilis patients had increases in RPR titers immediately following treatment, these changes rarely influenced assessment of therapeutic outcome. Only 3% of patients treated would have been reclassified.

Serologic Response to Treatment in Human Immunodeficiency Virus-Negative Syphilis Patients Using Automated Serological Tests: Proposals for New Guidelines

“…These results were consistent with a prior report of nontreponemal titer variation in the two weeks following initiation of syphilis treatment13. Because of the high variation in the first six months following treatment, we concluded that evaluating seroreversion during the first six months following treatment is not necessary.…”

Management of Adult Syphilis: Key Questions to Inform the 2015 Centers for Disease Control and Prevention Sexually Transmitted Diseases Treatment Guidelines: Table 1.

“…Sena et al found that lower pretreatment RPR titers among persons with early syphilis increased the probability of being serofast 6 months after therapy [34]. A study by Holman et al suggested some variability in RPR titers in the first 14 days following therapy that did not impact treatment results at 6 months [29]. Pastusczcak et al found that the detection of treatment failures during the first 3 months following syphilis therapy was quite low [32].…”

A Nodular-Ulcerative Form of Secondary Syphilis in Aids

“…Repeat syphilis testing before these specifi ed times can create confusion, as the RPR may increase immediately after therapy of early syphilis, and the initial RPR may underestimate the maximal titer ( 12 ). In our case, the early rise in RPR posttherapy was uninterpretable, but likely was not signifi cant.…”