1. Department of Internal Medicine, Chung-Ang University College of Medicine, Seoul, Korea
2. Department of Gastroenterology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
3. Department of Gastroenterology, Inje University Ilsan Paik Hospital, Inje University College of Medicine, Goyang, Korea
4. Department of Clinical Epidemiology and Biostatistics, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
5. Department of Internal Medicine, St. Vincent’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea
6. Department of Internal Medicine, Biomedical Research Institute, Pusan National University Hospital, Pusan National University School of Medicine, Busan, Korea
7. Department of Internal Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
8. Department of Internal Medicine, Konkuk University School of Medicine, Seoul, Korea
9. Department of Internal Medicine, Gyeongsang National University Changwon Hospital, Gyeongsang National University College of Medicine, Changwon, Korea