1. Department of Medicine, University of British Columbia, British Columbia Centre for Excellence in HIV/AIDS, Vancouver, BC, Canada
2. Clinical Addiction Research and Education Unit, Section of General Internal Medicine, Department of Medicine, Boston University School of Medicine and Boston Medical Center, Boston, MA, USA
3. Department of Biostatistics, Boston University School of Public Health, Boston, MA, USA
4. Data Coordinating Center, Boston University School of Public Health, Boston, MA, USA
5. Section of Infectious Diseases, Department of Medicine, Boston University School of Medicine and Boston Medical Center, Boston, MA, USA
6. Department of Community Health Sciences, Boston University School of Public Health, Boston, MA, USA