1. Department of Internal Medicine, Chonnam National University Medical School, Gwangju, Korea
2. Department of Internal Medicine, Chung-Ang University College of Medicine, Seoul, Korea
3. Department of Internal Medicine, Kosin University College of Medicine, Busan, Korea
4. Department of Internal Medicine, Inha University School of Medicine, Incheon, Korea
5. Department of Internal Medicine, Kyung Hee University Hospital, Seoul, Korea
6. Department of Internal Medicine, Eunpyeong St. Mary's Hospital, College of Medicine, the Catholic University of Korea, Seoul, Korea
7. Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea