1. Department of Gastroenterology, Oslo University Hospital, Postboks 4959 Nydalen, 0424 Oslo, Norway
2. University of Oslo, Institute of Health and Society, Postboks 1072 Blindern, 0316 Oslo, Norway
3. Telemark Hospital Trust, O&U, 3710 Skien, Norway
4. Institute of Clinical Medicine, University of Oslo, Postboks 1072 Blindern, 0316 Oslo, Norway
5. Health Science, Østfold University College, Postboks 700, 1757 Halden, Norway
6. Department of Gastroenterology, Østfold Hospital Trust, Sarpsborg, Norway