1. Division of Gastroenterology, Department of Internal Medicine, Inha University School of Medicine, Incheon, South Korea
2. Yonsei University College of Medicine, Seoul, South Korea
3. Soon Chun Hyang University School of Medicine, Cheonan Hospital, Cheonan, South Korea
4. Ajou University School of Medicine, Suwon, South Korea
5. Occupational and Environmental Medicine, Inha University School of Medicine, Incheon, South Korea