Open Access Highly Accessed Research article

Predictors of serological failure after treatment in HIV-infected patients with early syphilis in the emerging Era of universal antiretroviral therapy use

Sadao Jinno14*, Bryan Anker1, Parveen Kaur1, Claire C Bristow2 and Jeffrey D Klausner3

Author Affiliations

1 Department of Medicine, AIDS Healthcare Foundation, Los Angeles, CA USA

2 Fielding School of Public Health, University of California, Los Angeles, CA USA

3 Division of Infectious Diseases, Program in Global Health, University of California, Los Angeles, CA USA

4 1300 N. Vermont Ave. #407, Los Angeles, CA 90027, USA

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BMC Infectious Diseases 2013, 13:605  doi:10.1186/1471-2334-13-605

Published: 26 December 2013



The optimal treatment of early syphilis (primary, secondary and early latent) in HIV-infected patients remains controversial. The Center for Diseases Control STD Treatment Guidelines recommended 1 dose of benzathine penicillin G (BPG) regardless of HIV infection. However, many providers modify the treatment for early syphilis.


We performed a retrospective chart review of all cases of early syphilis with positive serologic test results in HIV-infected patients from May 2006 to May 2011 in 2 large, urban HIV clinics. Early syphilis includes primary, secondary, and early latent syphilis. Serological failure was defined as a lack of 4-fold decrease in rapid plasma reagent (RPR) titers 9 to 12 months after syphilis treatment. Patients whose RPR titers decreased after treatment and subsequently increased 4-fold at 9 to 12 months were excluded from the analysis of serological response because of possibility as “reinfection”. Baseline characteristics were tested as predictive factors of serological failure using a univariate and multivariate logistic regression model, respectively.


Of 560 patients with confirmed cases of early syphilis, 51 (9.0%) experienced serological failure. Multivariate logistic regression modeling demonstrated that the predictive factors associated with serological failure after early syphilis treatment were baseline RPR titer ≤ 1:16 (OR 3.91 [95% CI, 2.04-7.47]), a previous history of syphilis (OR 3.12 [95% CI, 1.55-6.26]), and a CD4 T-cell count below 350 cells/ml (OR 2.41 [95% CI, 1.27-4.56]). Of note, type of syphilis treatment (1 dose versus 3 doses of BPG) did not appear to affect the proportion of serological failure (4% versus 10%, P = 0.29), however the power of this study to detect small differences was limited.


HIV-infected patients with baseline RPR titer ≤1:16, syphilis history, and/or a CD4 T-cell count <350 cells/ml should be closely monitored for serologic failure after early syphilis treatment. This study did not detect a substantial difference between treatment with > 1 dose of BPG and decreased frequency of serological failure, supporting the current recommendation that one dose of BPG is adequate treatment for early syphilis in HIV-infected patients.

Syphilis; HIV; Serological failure; Benzathine penicillin