1. Department of Internal Medicine, School of Medicine, Kyungpook National University, Daegu, Korea
2. Department of Internal Medicine, Soonchunhyang University College of Medicine, Bucheon, Korea
3. Department of Internal Medicine, Chonbuk National University Hospital, Jeonju, Korea
4. Department of Internal Medicine, Inha University Hospital, Incheon, Korea
5. Department of Internal Medicine, Institute of Gastrointestinal Medical Instrument Research, Korea University College of Medicine, Seoul, Korea