1. Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea.
2. Department of Preventive Medicine, Seoul National University College of Medicine, Seoul, Korea.
3. Medical Research Collaborating Center, Seoul National University Hospital and Seoul National University College of Medicine, Seoul, Korea.
4. Division of Nephrology, Department of Internal Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
5. Department of Internal Medicine, The Catholic University of Korea, Seoul St. Mary's Hospital, Seoul, Korea.
6. Department of Internal Medicine, Gachon University, Gil Hospital, Incheon, Korea.
7. Department of Internal Medicine, Dongguk University Gyeongju Hospital, Gyeongju, Korea.
8. Department of Internal Medicine, Seoul National University Boramae Medical Center, Seoul, Korea.