1. Central Interdisciplinary Endoscopy Unit, Department of Gastroenterology, Charité University Medical Hospitals, Berlin, Germany
2. Department of Medicine, Division of Gastroenterology and Hepatology, Oregon Health and Science University, Portland, Oregon, USA
3. Private gastroenterology offices, Berlin, Germany
4. Department of Interdisciplinary Endoscopy, University Hospital Hamburg-Eppendorf, Hamburg, Germany
5. Private statistical office, Berlin, Germany
6. Central Research Institute of Ambulatory Health Care, Berlin, Germany