1. Center for Clinical Epidemiology, Odense University Hospital , 5000 Odense C , Denmark
2. Research Unit of Clinical Epidemiology, Department of Clinical Research, University of Southern Denmark , 5000 Odense C , Denmark
3. Department of Medical Gastroenterology, Hospital of Southwest Jutland , Esbjerg , Denmark
4. Department of Regional Health Science, University of Southern Denmark , Esbjerg , Denmark
5. Department of Medical Gastroenterology S, Odense University Hospital , 5000 Odense C , Denmark
6. Research Unit of Medical Gastroenterology, Department of Clinical Research, University of Southern Denmark , 5000 Odense C , Denmark