[1] Univ Michigan Hlth Syst, Dept Internal Med, Div Gastroenterol, Taubman Ctr 3912, Ann Arbor, MI 48109 USA
[2] Univ Nebraska Med Ctr, Eppley Inst Res Canc, Omaha, NE USA
[3] Univ Pittsburgh, Med Ctr, Div Gastroenterol, Pittsburgh, PA USA
[4] Creighton Univ, Sch Med, Dept Prevent Med, Omaha, NE 68178 USA
[5] Univ Genoa, Dept Internal Med & Med Specialties, Genoa, Italy
[6] Northshore Univ Hlth Syst, Dept Med, Evanston, IL USA
[7] Univ Chicago, Pritzker Sch Med, Chicago, IL 60637 USA
[8] Univ Nebraska Med Ctr, Dept Surg, Omaha, NE USA
[9] Univ Alabama Birmingham, Dept Pathol, Birmingham, AL 35294 USA
[10] Univ Michigan, Sch Publ Hlth, Dept Biostat, Ann Arbor, MI 48109 USA
[11] Univ Pittsburgh, Dept Biostat, Med Ctr, Pittsburgh, PA 15261 USA