[1] Johns Hopkins Univ, Welch Ctr Prevent Epidemiol & Clin Res, Baltimore, MD 21287 USA
[2] Johns Hopkins Univ, Sch Med, Dept Med, Baltimore, MD 21287 USA
[3] Johns Hopkins Bloomberg Sch Publ Hlth, Dept Epidemiol, Baltimore, MD USA
[4] Johns Hopkins Bloomberg Sch Publ Hlth, Dept Hlth Policy & Management, Baltimore, MD USA
[5] Johns Hopkins Bloomberg Sch Publ Hlth, Dept Hlth Behav & Soc, Baltimore, MD USA
[6] Amer Coll Physicians, Div Med Practice Professionalism & Qual, Washington, DC USA