[1] Univ Western Ontario, Dept Epidemiol & Biostat, London, ON, Canada
[2] Global Forum MSM & HIV, Oakland, CA USA
[3] Univ Calif San Francisco, Community Hlth Syst, San Francisco, CA 94143 USA
[4] Univ Calif San Francisco, Dept Med, San Francisco, CA USA
[5] San Francisco Dept Publ Hlth, San Francisco, CA USA
[6] Columbia Univ, Int Ctr AIDS Care & Treatment Programs ICAP, Mailman Sch Publ Hlth, New York, NY USA
[7] Columbia Univ, Dept Socialmed Sci, Mailman Sch Publ Hlth, New York, NY USA