[1] Oslo Univ Hosp, Dept Gastroenterol, Oslo, Norway
[2] Univ Oslo, Inst Clin Med, Oslo, Norway
[3] Lovisenberg Diaconal Hosp, Unger Vetlesen Inst, Oslo, Norway
[4] Lovisenberg Diaconal Hosp, Dept Gastroenterol, Oslo, Norway
[5] Oslo Metropolitan Univ, Dept Publ Hlth, Oslo, Norway
[6] Vestfold Hosp Trust, Dept Gastroenterol, Tonsberg, Norway
[7] Diakonhjemmet Hosp, Dept Med, Oslo, Norway
[8] Akershus Univ Hosp, Dept Gastroenterol, Lorenskog, Norway
[9] Vestre Viken Hosp Trust, Dept Internal Med, Baerum Hosp, Gjettum, Norway
[10] Ostfold Hosp Trust, Dept Gastroenterol, Sarpsborg, Norway
[11] Innlandet Hosp Trust, Dept Internal Med, Gjovik, Norway
[12] Telemark Hosp Trust, Dept Gastroenterol, Skien, Norway
[13] Ostfold Univ Coll, Fac Hlth Welf & Org, Fredrikstad, Norway
[14] Univ Oslo, Inst Hlth & Soc, Dept Publ Hlth, Oslo, Norway
[15] Sorlandet Hosp Flekkefjord, Dept Internal Med, Flekkefjord, Norway
[16] Oslo Univ Hosp, Dept Paediat, Oslo, Norway