1. Institute for Digestive Research, Digestive Disease Center Soonchunhyang University College of Medicine, Seoul, Korea
2. Department of Internal Medicine, Soonchunhyang University College of Medicine, Bucheon, Gyeonggi-do, Korea
3. Division of Gastroenterology, Cheonan Hospital, Soonchunhyang University College of Medicine, Cheonan, Chungcheongnam-do, Korea
4. Department of biostatistics, Soonchunhyang University Seoul Hospital, Seoul, Korea