Identification of clients at highest risk of acquiring human immunodeficiency virus (HIV) is a critical component to PrEP implementation. CDC published clinical practice guidelines for identifying individuals as PrEP candidates in 2014 and developed a risk-screening tool: HIV Incidence Risk Index for MSM (HIRI-MSM). Gilead also listed factors to identify individuals at high risk in the package insert. We examined the performance of CDC guidelines, HIRI-MSM and Gilead recommendations in identifying eligible PrEP candidates, including seroconverters, in a population-based sample of young Black men who have sex with men (YBMSM).
We followed a population-based cohort of YBMSM aged 16-29 years during PrEP roll-out in Chicago from 2013-2016 (n=618). We computed the proportion of YBMSM with indications for PrEP using CDC guidelines, HIRI-MSM, and Gilead recommendations. We also calculated the sensitivity and specificity of guidelines in predicting HIV seroconversion. HIV seroconversion was measured using 4th generation and NAAT testing at three time points. Incidence Rate Ratios using Poisson regression were computed to compare sociodemographic and network factors associated with HIV incidence.
In the study cohort, 300 HIV uninfected YBMSM contributed 390.4 person-years (PY) of follow-up. The mean age at baseline was 22.3 years (SD=3.07), HIV incidence was 8.5 cases per 100 PY (95% CI, 6.0-11.9). Overall, 49% had an indication for PrEP using CDC guidelines; 72% using HIRI-MSM, and 86% using Gilead recommendations. HIV seroconverters (n=33) were identified as PrEP eligible prior to seroconversion with sensitivity/specificity of CDC, HIRI-MSM and Gilead guidelines of: 52%/52%; 85%/30%; and 94%/15%. HIV incidence did not differ significantly by individual risk behaviors that comprise indications for PrEP: condomless anal sex (IRR 1.2, 95% CI: 0.6-2.3); drug use (IRR 1.2, 0.6, 2.3); serodiscordant partnership (IRR 0.3, 95% CI 0.04, 1.9). Having a partner ≥ 10 years older was predictive of HIV incidence (IRR 2.1, 95% CI 1.0-4.5).
Low sensitivity of CDC guidelines and limited specificity of HIRI-MSM and Gilead screening tools is of concern for PrEP implementation in most at risk populations. Consideration of local epidemiology and network factors may better guide identification of clients who could benefit the most from PrEP.