[1] Univ Penn, Div Gastroenterol & Hepatol, Perelman Sch Med, Philadelphia, PA 19104 USA
[2] Univ Penn, Div Gastroenterol, Perelman Sch Med, Philadelphia, PA 19104 USA
[3] Univ Penn, Ctr Clin Epidemiol & Biostat, Perelman Sch Med, Philadelphia, PA 19104 USA
[4] Penn State Univ, Dept Vet & Biomed Sci, University Pk, PA 16802 USA
[5] Univ Penn, Div Gastroenterol & Hepatol, Dept Med, Perelman Sch Med, Philadelphia, PA 19104 USA
[6] Univ Penn, Philadelphia, PA 19104 USA