1. Division of Gastroenterology and Hepatology, Department of Internal Medicine, Ansan Hospital, Korea University College of Medicine, Ansan, Korea
2. Department of Gastroenterology, University of Ulsan College of Medicine, Seoul, Korea
3. Division of Gastroenterology, Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea
4. Department of Internal Medicine, Ewha Womans University College of Medicine, Seoul, Korea
5. Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea
6. Division of Gastroenterology and Hepatology, Department of Internal Medicine, Anam Hospital, Korea University College of Medicine, Seoul, Korea