Risk Factors for Anal Human Papillomavirus Infection Type 16 Among HIV-Positive Men Who Have Sex With Men in San Francisco

Background: HIV-positive men who have sex with men (MSM) are at high risk of anal cancer compared with the general population. Human papillomavirus (HPV) infection, particularly HPV 16, is causally associated with anal cancer. However, the risk factors for anal HPV 16 infection are poorly understood. We determined the prevalence and risk factors for anal HPV 16 infection in a population of HIV-positive MSM, most of whom were being treated with antiretroviral therapy. Design: Cross-sectional data from the baseline visit of a 4-year prospective cohort study. Methods: Three hundred forty-eight HIV-positive MSM were recruited in San Francisco, and they received a detailed sexual behavior risk factor questionnaire. An anal swab was used to collect specimens for HPV type-specific DNA testing using L1 HPV DNA polymerase chain reaction. We used log-binomial multivariable models to determine the risk factors for anal HPV 16 infection. Results: Ninety-two percent of HIV-positive MSM had at least 1 anal HPV type, 80% had at least 1 oncogenic HPV type, and 42% had HPV 16. Non-Hispanic white race and higher level of education were associated with a decreased risk of HPV 16 infection. A higher number of total male partners was associated with HPV 16 (relative risk: 1.6, 95% confidence interval 1.1 to 2.4, P = 0.01) for 201-1000 partners compared with 1-200. Injection drug use was independently associated with anal HPV 16 infection (relative risk: 1.5, 95% confidence interval 1.2 to 1.9, P = 0.003). Conclusions: The prevalence of anal HPV infection, including HPV 16, is high in HIV-positive MSM. HIV-positive MSM should be counseled about the risk associated with increased partners and injection drug use.