1. Department of Internal Medicine, Division of Gastroenterology, Landspitali-The National University Hospital of Iceland, Reykjavik, Iceland
2. deCODE genetics/Amgen Inc., Reykjavik, Iceland
3. Faculty of Pharmaceutical Sciences, University of Iceland, Reykjavik, Iceland
4. Department of Clinical and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway