[1] Univ Penn, Perelman Sch Med, Dept Med, Philadelphia, PA 19104 USA
[2] Philadelphia VA Med Ctr, Dept Med, Philadelphia, PA USA
[3] Univ Calif San Francisco, Dept Med, San Francisco, CA USA
[4] Univ Penn, Ctr Clin Epidemiol & Biostat, Philadelphia, PA 19104 USA
[5] Univ Illinois, Dept Med, Chicago, IL USA
[6] Univ Michigan, Dept Med, Ann Arbor, MI 48109 USA
[7] Cleveland Clin Fdn, Dept Med, Cleveland, OH USA
[8] Univ Penn, Dept Biostat & Epidemiol, Philadelphia, PA 19104 USA
[9] Univ Penn, Ctr Clin Epidemiol & Biostat, Perelman Sch Med, Philadelphia, PA 19104 USA
[10] Kaiser Permanente Calif, Dept Med, Dept Epidemiol & Biostat, Div Res, Oakland, CA USA