1. Department of Internal Medicine, Dongguk University College of Medicine, Gyeongju, Korea.
2. Department of Internal Medicine, Institute of Digestive Disease and Nutrition, Korea University College of Medicine, Seoul, Korea.
3. Department of Internal Medicine, Kyung Hee University School of Medicine, Seoul, Korea.
4. Department of Internal Medicine, KEPCO Medical Center, Seoul, Korea.
5. Department of Internal Medicine, Soonchunhyang University College of Medicine, Bucheon, Korea.
6. Department of Internal Medicine, Seoul St. Mary's Hospital, The Catholic University of Korea College of Medicine, Seoul, Korea.