1. Institute for Digestive Research, Soonchunhyang University Seoul Hospital, Seoul, Korea.
2. Department of Internal Medicine, Ewha Medical Research Institute, Ewha Womans University College of Medicine, Seoul, Korea.
3. Department of Internal Medicine, Keimyung University School of Medicine, Daegu, Korea.
4. Department of Internal Medicine, Dankook University College of Medicine, Cheonan, Korea.
5. Department of Internal Medicine, Chonnam National University Hospital, Gwangju, Korea.
6. Department of Internal Medicine, Wonkwang University School of Medicine, Iksan, Korea.
7. Division of Gastroenterology, Department of Internal Medicine, Kyung Hee University School of Medicine, Seoul, Korea.
8. Department of Internal Medicine, Soonchunhyang University College of Medicine, Cheonan Hospital, Cheonan, Korea.
9. Department of Biostatistics, Soonchunhyang University Seoul Hospital, Seoul, Korea.