Background: United States syphilis rates have increased to levels last seen in the 1990s. We examined syphilis epidemiology of patients attending a Boston community health center specializing in sexual and gender minority health.
Methods: We performed a retrospective cohort study of all patients assigned male at birth screened with rapid plasma reagin from 2005 through 2015. We developed an algorithm to identify new infections and used repeat cross-sectional analysis to assess temporal trends in syphilis diagnoses. We also performed longitudinal analysis to calculate syphilis incidence using a Cox proportional hazards model that accounts for multiple infections over time.
Results: Eighteen thousand two hundred eighty-two patients had a total of 57,080 rapid plasma reagins, 1170 (2.0%) tests met criteria for syphilis. Adjusted syphilis diagnoses increased from 1.2% to 1.9%, recurrent syphilis diagnoses increased from 0.04% to 0.3% during the study period. Black and Hispanic/Latinx patients, patients aged 35 to 44 years, gay/bisexual patients, cisgender men, and human immunodeficiency virus (HIV)-infected patients and those who became HIV-infected during the study period were more likely to test positive for syphilitic infection in repeat cross-sectional analysis. Among 6199 patients screened more than 1 time over 21,745 person-years, there were 661 new syphilis cases (3.0% annual incidence; 95% confidence interval [CI], 2.8% to 3.2%). Compared with those aged 14 to 24 years, patients 45 years or older were less likely to experience syphilis. New HIV infection was associated with increased risk of incident syphilis (adjusted hazard ratio, 2.87; 95% CI, 1.61-5.13). Virally suppressed HIV-infected patients were less likely to experience incident syphilis (adjusted hazard ratio, 0.69; 95% CI, 0.55-0.87).
Conclusions: The high incidence of syphilis among patients assigned male at birth disproportionately affected young patients, black and Hispanic/Latinx patients, gay/bisexual patients, cisgender men, and those with new or chronic HIV infection. Syphilitic reinfection rates increased over time.