1. Department of Medicine, Greater Los Angeles Veterans Affairs, Los Angeles, California.
2. Department of Biostatistics, Boston University School of Public Health, Boston, Massachusetts.
3. Harvard School of Public Health, Boston, Massachusetts.
4. Divisions of General Medicine, Infectious Disease, and Partners AIDS Research Center, Massachusetts General Hospital, Boston, Massachusetts.
5. Department of Epidemiology, Boston University School of Public Health, Boston, Massachusetts.
6. Divisions of General Medicine, Infectious Disease, and Partners AIDS Research Center, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.