1. Academic Department of Gastroenterology; Medical School of National and Kapodistrian University of Athens, Laiko General Hospital of Athens; Athens Greece
2. 4th Department of Internal Medicine; Medical School of Aristotle University, Hippokration General Hospital of Thessaloniki; Thessaloniki Greece
3. IFI Institute at Asklepios Klinik St. Georg; University of Hamburg; Hamburg Germany
4. Department of Hygiene, Epidemiology, and Medical Statistics; Medical School of National and Kapodistrian University of Athens; Athens Greece