High Risk of Syphilis Infection, Reinfection and Treatment Failure Among HIV-Infected Patients in Care in North Carolina

Background:  A high prevalence of syphilis infection has been observed among HIV-infected populations, especially men who have sex with men (MSM). We assessed the incidence of syphilis infections, reinfections and treatment failures among HIV-infected patients seen at an infectious disease clinic in North Carolina. 

Methods:  We conducted a retrospective chart review of HIV-infected subjects enrolled in an HIV clinical cohort study between January 1996 and December 2012. Syphilis infections were identified from diagnosis codes and adjudicated by a physician in concordance with published criteria. We calculated incidence rates of syphilis infection. Subjects contributed time from their entry to care until loss to follow-up, death, or December 2015, and were followed for three years after the first syphilis diagnosis. Multivariable regression models were conducted to estimate relative risks (RR) of reinfection or treatment failure.

Results: Overall, 4,048 subjects contributed 38,352 person-years. The incidence rate of syphilis was 17 infections per 1,000 person-years; 522 (12%) patients had at least one syphilis diagnosis during the study period. After exclusion of 150 patients who were lost to follow-up or died before three years, 372 remained in the analysis including 69% MSM, 13% women and 67% Black. The stage of syphilis diagnosis was 4% primary, 16% secondary, 11% latent, 6% neurosyphilis, and 63% of unknown stage; 58 patients (16% [95% CI: 12%-20%]) met criteria for syphilis reinfection or treatment failure. In multivariable analyses, subjects with a history of ≥ 6 sexually transmitted infections had a RR of 2.85 (95% CI: 1.73, 4.69), while those with a history of hepatitis C had a RR of 0.26 (95% CI: 0.10, 0.70) for reinfection or treatment failure. 

Conclusions:  HIV infected patients are at high risk of syphilis infection, reinfection and treatment failure, reinforcing the importance of frequent testing and follow-up of sexually transmitted infections among patients in HIV clinical care.