1. Department of Internal Medicine, Gangneung Asan Hospital, University of Ulsan College of Medicine, Gangneung, Gangwon-do, Korea
2. Department of Gastroenterology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea
3. Department of Gastroenterology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
4. Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea
5. Department of Internal Medicine, Ewha Womans University School of Medicine, Seoul, Korea
6. Department of Clinical Epidemiology and Biostatistics, Asan Medical Center, Seoul, Korea
7. Department of Internal Medicine, Hanyang University School of Medicine, Seoul, Korea