[1] Helsinki Univ Hosp, Dept Gastroenterol, Helsinki, Finland
[2] Hyvinkaa Hosp, Endoscopy Outpatient Clin, Hyvinkaa, Finland
[3] Helsinki Univ Hosp, Head & Neck Ctr, Helsinki, Finland
[4] Peijas Hosp, HUS Diagnost Ctr, Clin Physiol Unit, Vantaa, Finland
[5] Univ Eastern Finland, Dept Hlth & Social Management, Kuopio, Finland
[6] Univ Helsinki, Dept Publ Hlth, Helsinki, Finland
[7] Aava Kamppi Med Ctr, Dept Gastroenterol, Helsinki, Finland
[8] Univ Helsinki, Dept Med, Helsinki, Finland