1. Institute for Digestive Research, Digestive Disease Center, Soonchunhyang University Hospital, Seoul, Korea.
2. Department of Internal Medicine, Soonchunhyang University College of Medicine, Bucheon, Korea.
3. Department of Internal medicine, Sungbuk Central Hospital, Seoul, Korea.
4. Department of Internal Medicine, Eulji General Hospital, Eulji University College of Medicine, Seoul, Korea.