[1] Univ Penn, Sch Med, Div Gastroenterol, Philadelphia, PA 19104 USA
[2] Univ Penn, Sch Med, Ctr Clin Epidemiol & Biostat, Philadelphia, PA 19104 USA
[3] Univ Penn, Sch Med, Dept Med, Philadelphia, PA 19104 USA
[4] Univ Penn, Sch Med, Dept Biostat & Epidemiol, Philadelphia, PA 19104 USA
[5] Massachusetts Gen Hosp, Boston, MA 02114 USA
[6] Univ Chicago, Chicago, IL 60637 USA
[7] Case Western Reserve Univ, Cleveland, OH 44106 USA
[8] Cleveland Clin, Cleveland, OH 44106 USA
[9] Mt Sinai Sch Med, New York, NY USA