[1] Brigham & Womens Hosp, Div Gen Med & Primary Care, Dept Med, Boston, MA 02115 USA
[2] Partners Healthcare Syst, Ctr Appl Med Informat Syst Res, Boston, MA USA
[3] Harvard Univ, Sch Med, Boston, MA USA
[4] Univ Calif San Francisco, UCSF Coordinating Ctr, Dept Med, San Francisco, CA 94143 USA
[5] Univ Calif San Francisco, Dept Epidemiol & Biostat, San Francisco, CA 94143 USA