1. Department of Internal Medicine, Division of Gastroenterology and Hepatology, Landspitali University Hospital, Reykjavik, Iceland;
2. Faculty of Medicine, University of Iceland, Reykjavik, Iceland;
3. Department of Pathology, Landspitali University Hospital, Reykjavik, Iceland;
4. Icelandic Cancer Registry, Iceland Cancer Society, Krabbameinsfelagid Island, Reykjavik, Iceland