[1] Cambridge Univ Hosp NHS Fdn Trust, Dept Gastroenterol, Addenbrookes Hosp, Cambridge CB2 0QQ, England
[2] UCL, Res Council Clin Trials Unit, London, England
[3] Dartmouth Hitchcock Med Ctr, Sect Gastroenterol & Hepatol, Inflammatory Bowel Dis Ctr, Lebanon, NH USA
[4] Geisel Sch Med, Dartmouth Inst Hlth Policy & Clin Practice, Hanover, NH USA