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Background:Many HIV-infected men who have sex with men (MSM) remain at high risk of acquiring other sexually transmitted infections (STIs). Identifying those at greatest risk of acquiring STIs can guide screening recommendations.
Methods: We developed and validated a risk score to predict asymptomatic STI incidence (early latent syphilis, rectal and pharyngeal gonorrhea, and rectal and pharyngeal chlamydial infection) among HIV-infected MSM using medical record data from a public STD clinic. We randomly divided the data in half and used one dataset for risk score development and the other for internal validation. A stepwise selection procedure using the Akaike Information Criterion was used to identify the most parsimonious Cox proportional hazards model with time-varying covariates and recurrent failures. Censoring occurred at the individual’s last visit.
Results: From 2006-2012, a total of 1664 HIV-infected MSM received care in the clinic, of whom 780 (46%) tested for STIs >1 time before 11/20/2013. These men acquired 524 asymptomatic STIs over 2129 years of follow-up (incidence = 25 per 100 person-years). The prediction model included the following risk factors, each of which pertained to the year prior to clinical evaluation: diagnosis of ≥1 STI (contribution to score: +5), unprotected anal sex with an HIV-infected man (+3), methamphetamine use (+3), and ≥10 male sex partners (+2). Risk scores ranged from 0-13. In the validation dataset, a one-point increase in score resulted in an average 1.10-fold increase in the rate of asymptomatic STIs. Men with a risk score ≥7 had a 2.0-fold increase in risk (95% CI: 1.6-2.6) compared with those with scores ≤6 (33 vs. 16 per 100 person-years, p<0.001). These higher risk men represented 48% of visits.
Conclusions: We developed a risk score predictive of asymptomatic STI acquisition among HIV-infected MSM that may assist providers in targeting frequent screening to the highest risk men.