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Sexually transmitted infection incidence relative to time since care entry in a longitudinal HIV clinical cohort
A.J. Mayo1, S. Napravnik2, B. Stalzer2, E.B. Quinlivan2, J.J. Eron2
1University of North Carolina Gillings School of Global Public Health, Epidemiology, Chapel Hill, United States, 2University of North Carolina, Department of Medicine, Chapel Hill, United States
Background: Since reducing high risk sexual behavior among HIV-infected individuals is a priority, we estimated incidence rates (IR) of Neisseria gonorrhoeae (GC), Chlamydia trachomatis (CT), Trichomonas vaginalis (TV), and primary and secondary (early) syphilis among HIV-infected individuals receiving primary HIV care in the Southeastern U.S.
Methods: Patients enrolled in the UNC CFAR HIV Clinical Cohort study contributed person-time from the first of January 2000 or entry to UNC HIV care, until the last of December 2007, loss to follow-up or death. Generalized estimating equations (GEE) using a Poisson distribution and a log-link function with an exchangeable correlation matrix were fit to estimate IRs, incidence rate ratios (IRR), and robust 95% confidence intervals (CI).
Results: Of 2,010 HIV-infected patients, 174 (9%) acquired ≥1 STI. Of these 174, 25% had multiple infections (range: 2-6 STI events). During 9,129 person-years of follow-up, there were 239 STI diagnoses (TV=127; GC=43; CT=43; early syphilis=33) for an overall IR of 2.6/100 person-years (95%CI: 2.3, 3.1). STI incidence was higher among women compared to men [IR=5.3; 95%CI: (4.3, 6.5) vs. IR=1.4; 95%CI: (1.1, 1.9)] although when TV was excluded, rates were similar (IR=1.2 and 1.3, among women vs men). Female gender, younger age, African-American race, HIV RNA>400 copies/ml, substance abuse, living < 30 miles from the clinic, and delaying HIV care entry by >90 days were all significantly associated with increased STI incidence in multivariable predictive models (all P< 0.05). STI incidence was consistently increased during the first two years after care entry compared to later years of care (IRR=1.6; 95%CI: 1.1, 2.4).
Conclusions: Regular care for HIV is also beneficial towards reducing STI incidence; however, rates did not decline until patients were in care for more than two years. Targeting HIV-prevention efforts and STI screening to patients during the early years after care entry might be especially important.
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