To develop and validate an easy-to-use prediction model for HIV acquisition among men who have sex with men (MSM).
We developed prediction models using medical records data from an STD clinic (2001–2008) and validated these models using data from the control arm of Project Explore, an HIV prevention trial (1999–2003).
Of 1903 MSM who tested for HIV more than once in the development sample, 101 acquired HIV over 6.7 years of follow-up. Annual HIV incidence was 2.57% (95% confidence interval [CI]: 2.09%, 3.12%). During 4 years of follow-up of 2081 Project Explore control arm participants, 144 acquired HIV for an incidence of 2.32% (95% CI: 1.96%, 2.73%). A prediction model that included variables indicating use of methamphetamine or inhaled nitrites in the prior 6 months, unprotected anal intercourse with a partner of positive or unknown HIV status in the prior year, ≥10 male sex partners in the prior year, and current diagnosis or history of bacterial sexually transmitted infection was well calibrated overall (expected-observed ratio = 1.01; 95% CI: 0.97, 1.05) and had modest discriminatory accuracy at 1 year (area under the receiver-operator characteristic curve = 0.67; 95% CI: 0.60, 0.75) and at 4 years (area under the receiver-operator characteristic curve = 0.66; 95% CI: 0.61, 0.71). Over 4 years, cumulative incidence ranged from 3.9% to 14.3% for groups of men defined by the prediction model.
A new risk score was predictive of HIV acquisition and could assist providers in counseling MSM and in targeting intensified prevention to MSM at greatest risk for HIV infection. Its accuracy requires further evaluation.
A validated prediction model for human immunodeficiency virus acquisition among men who have sex with men may prove useful in counseling men who have sex with men and in prioritizing prevention efforts to men who have sex with men at highest risk.
From the *The Center for AIDS and STD, University of Washington, Seattle, Washington; †Department of Epidemiology, University of Washington, Seattle, Washington; ‡Department of Public Health—Seattle and King County, Seattle, Washington; and Departments of §Global Health, ∥Medicine, and ¶Biostatistics, University of Washington, Seattle, Washington
The authors thank Deborah Donnell and Marla Husnik from the Statistical Center for HIV/AIDS Research and Prevention and Roxanne Kerani and Fred Koch from Public Health—Seattle and King County for their technical assistance.
Project Explore was supported by the HIV Prevention Trials Network and sponsored by the National Institutes of Health and the US Office of AIDS Research and also supported by NIH T32 AI07140 (to T.W.M.).
Project Explore was not conducted independent of the funding sources. However, funding organizations had no involvement in the current study’s design; data collection, analysis, or interpretation; or in the decision to publish this manuscript.
Correspondence: Timothy W. Menza, BA, Harborview Medical Center, 325 Ninth Ave, Box 359931, Seattle, WA 98104. E-mail: email@example.com.
Received for publication January 10, 2009, and accepted April 1, 2009.