1. Department of Family and Community Medicine, College of Medicine, King Saud University, P.O. Box 11495, Riyadh, Saudi Arabia
2. College of Medicine, King Saud University, P.O. Box 11495, Riyadh, Saudi Arabia
3. Department of Medicine, College of Medicine, King Saud University, P.O. Box 11495, Riyadh, Saudi Arabia
4. Department of Clinical Medicine and Gastroenterology, Institute of Medicine, University of Bergen, Norway