HIV seroconversion among public sexually transmitted disease clinic patients: Analysis of risks to facilitate early identification

OBJECTIVES: We identified risks for HIV seroconversion among public sexually transmitted disease (STD) clinic patients. DESIGN: This was a retrospective cohort study conducted January 1993 through October 2002 of STD clinic attendees aged ≥12 years in Baltimore, Maryland. METHODS: A negative HIV enzyme immunoassay (EIA) test was required for staggered cohort entry. Observation time was 30 days to 3 years. The outcome for multivariate Poisson regression was HIV seroconversion (positive EIA and/or Western blot test) compared among patients with or without sexual risk behaviors, drug use, an STD diagnosis, and signs and symptoms at an initial HIV test. RESULTS: One hundred twenty-five HIV seroconversions occurred among 10,535 individuals and 13,693 person-years of observation, for an incidence of 0.91 HIV seroconversions per 100 person-years (95% confidence interval [CI]: 0.76 to 1.09). Median time to HIV seroconversion was 1.54 years (95% CI: 1.11 to 1.73). In multivariate analysis, increased HIV seroconversion risk was associated with older age, drug use, a sexual partner with syphilis or HIV, genital ulcers, and gonorrhea. HIV incidence per 100 person-years was 4.86 for subjects with an HIV-positive sexual partner, 3.06 for those with injection drug use, and 2.40 for those with genital ulcers. CONCLUSIONS: We found a high rate of HIV seroconversion among STD clinic patients with specific risks. Algorithms with HIV RNA testing targeted to patients at the highest risk for seroconversion may optimize prevention and resource utilization.