[1] Beth Israel Deaconess Med Ctr, Div Gastroenterol, 330 Brookline Ave, Boston, MA 02115 USA
[2] Beth Israel Deaconess Med Ctr, Div Gen Internal Med & Primary Care, Boston, MA 02115 USA
[3] Harvard Med Sch, Dept Hlth Care Policy, Boston, MA 02115 USA
[4] Univ Pittsburgh, Univ Ctr Social & Urban Res, Pittsburgh, PA USA
[5] Univ Pittsburgh, Dept Biomed Informat, Pittsburgh, PA USA
[6] Univ Pittsburgh, Med Ctr, Div Gastroenterol Hepatol & Nutr, Pittsburgh, PA USA
[7] Univ N Carolina, Div Gastroenterol & Hepatol, Sch Med, Chapel Hill, NC 27515 USA
[8] Kaiser Permanente Washington Hlth Res Inst, Washington, DC USA