[1] Harvard Univ, Sch Med, Dept Hlth Care Policy, Boston, MA 02115 USA
[2] Brigham & Womens Hosp, Dept Med, Div Gen Med & Primary Care, Boston, MA 02115 USA
[3] Brigham & Womens Hosp, Dept Med, Div Gastroenterol, Boston, MA 02115 USA
[4] Harvard Univ, Sch Publ Hlth, Dept Hlth Policy & Management, Boston, MA 02115 USA
[5] Hlth Canada, Westborough, MA USA
[6] Harvard Vanguard Med Associates, Boston, MA USA