Syphilis treatment response among HIV-discordant couples in Zambia and Rwanda

Abstract

Background: Syphilis continues to be a common sexually transmitted infection, despite the availability of inexpensive and effective treatment. Infection in human immunodeficiency virus (HIV)-discordant couples is important because syphilis increases the risk of HIV acquisition. Current US treatment guidelines recommend 1 dose of benzathine penicillin for early syphilis, irrespective of HIV status, but data from coinfected patients are limited.

Methods: Retrospective analysis of 1321 individuals in 2 African HIV-discordant couple cohorts was performed. Cox proportional hazards analysis and multivariable modeling were used to assess predictors of serologic response to treatment at 180 days and 400 days. Modeling was performed for all episodes of positive rapid plasma reagin (RPR) test results and on a subset with higher RPR titers (≥1:4).

Results: A total of 1810 episodes of syphilis among 1321 individuals were treated with penicillin between 2002 and 2008. Although a positive RPR was more common in the HIV-infected partners, HIV infection did not impact the likelihood of serologic response to therapy (odds ratio [OR], 1.001; P = .995). By 400 days, 67% had responded to therapy, 27% were serofast, and 6.5% had documented reinfection. Prevalent infections were more likely to remain serofast than incident infections (33% vs 20% at 400 days).

Conclusions: In 2 HIV-serodiscordant couple cohorts in Africa, incident syphilis had a very good likelihood of response to penicillin therapy, irrespective of HIV infection. This supports current Centers for Disease Control and Prevention treatment guidelines. A high proportion of prevalent RPR-positive infections remain serofast despite treatment.

Keywords: HIV/AIDS; Rwanda; Zambia; discordant couples; syphilis.

Figure 1.

Flowchart of treated episodes of positive rapid plasma reagin test result. Abbreviations: BPN, benzathine penicillin; RPR, rapid plasma reagin.

Figure 2.

Adjusted survival curve for human immunodeficiency virus (HIV)–negative (solid curve) and HIV-positive patients (dashed curve). Abbreviation: HIV, human immunodeficiency virus.

Figure 3.

Adjusted survival curve by incident (solid curve) or prevalent (dashed curve) disease.