[1] Univ Penn, Sch Med, Hosp Univ Penn, Div Gastroenterol,Dept Med, Philadelphia, PA 19104 USA
[2] Univ Western Ontario, Dept Epidemiol & Biostat, Robarts Res Inst, London, ON, Canada
[3] Univ Western Ontario, Dept Med, London, ON, Canada
[4] Univ Chicago, Med Ctr, Dept Med, Gastroenterol Sect, Chicago, IL 60637 USA
[5] Atlanta Gastroenterol Associates, Atlanta, GA USA
[6] Janssen Biotech Inc, Horsham, PA USA
[7] Johnson & Johnson PRD, Biostat, Edison, NJ USA
[8] Univ Calif San Diego, Div Gastroenterol, La Jolla, CA 92093 USA