1. Gastrounit, Medical Division, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark;
2. Department of Gastroenterology and Hepatology, Odense University Hospital, University of Southern Denmark, Odense, Denmark;
3. Department of Diagnostics, Clinical Physiology and Nuclear Medicine Section, Copenhagen University Hospital Glostrup, Glostrup, Denmark;
4. National Institute of Public Health, University of Southern Denmark, Copenhagen, Denmark