1. Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea.
2. Department of Internal Medicine, Seoul National University Hospital Healthcare System Gangnam Center, Seoul, Korea.
3. Department of Internal Medicine, Kangwon National University School of Medicine, Chuncheon, Korea.
4. Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, Korea.
5. Department of Internal Medicine, Seoul National University Boramae Medical Center, Seoul, Korea.
6. Department of Internal Medicine, Chung-Ang University College of Medicine, Seoul, Korea.