Risk Factors and Incidence of Syphilis in HIV Outpatients, (HOPS 1999-2015)

Risk factors and incidence of syphilis in HIV-infected persons, the HOPS, 1999-2015 BACKGROUND: The incidence of syphilis has been increasing, especially among gay, bisexual and other men who have sex with men (MSM) for at least a decade in the United States (U.S.). We assessed incidence, temporal trends and associated risk factors for newly diagnosed syphilis infections among HIV infected patients in care during a 15-year period. METHODS: We analyzed data from the HIV Outpatient Study (HOPS) cohort participants seen at ten U.S. HIV clinical practice sites from January 1, 1999 to June 30, 2015. New syphilis cases were defined based on a combination of established laboratory parameters as well as clinical diagnoses. We assessed incidence rates of syphilis by patient socio-demographic, clinical and behavioral characteristics, and performed multivariable Cox proportional hazards regression analyses of risk factors for new syphilis infections. RESULTS: We studied 6888 HIV-infected participants, among whom 641 had one or more new syphilis diagnoses during a median follow-up of 5.2 years (Interquartile range: 2.0 to 10.8). Most study participants were male (78%) and aged 31-50 years (Table) and 56% of participants were MSM, 28% heterosexuals, 10% persons who inject drugs (PWID) and 6% other/unknown risk. There were a total of 799 syphilis diagnoses for an overall incidence of 1.8 per 100 person-years (95% Confidence Interval [CI] 1.6-1.9). The crude incidence rate was higher among MSM than heterosexuals (2.6 vs. 0.7, P <0.001), was higher among participants aged 18-30 years than over 50 years (3.0 vs. 0.8, P<0.001), and was elevated among non Hispanic blacks vs. white and Hispanic/Latino participants (Table). Rates of diagnosed syphilis were highest in the most recent time period, 2011 2015, as compared with prior periods. In multivariable analyses, the independent risk factors for syphilis included (all P< 0.001): being aged 18-30 years (hazard ratio [HR] 1.8, CI 1.5-2.1) vs older, having MSM HIV risk (HR 4.4, CI 3.6-5.5) vs other HIV risks, being black, non Hispanic (HR 1.8, CI 1.5-2.1) vs other race/ethnicities, and being observed during 2011-2015 (HR 2.3, CI 1.7-3.0) vs earlier periods. CONCLUSIONS: The steady increases in the syphilis incidence rate through 2015, particularly among HIV-infected patients who are younger, black, non-Hispanic and MSM, reflect ongoing sexual risk. Results highlight need for enhanced and targeted prevention interventions in this population.