1. Department of Internal Medicine, Seoul National Univeristy College of Medicine, Seoul, Korea.
2. Department of Internal Medicine, Seoul National University Bundang Hosptial, Seongnam, Korea.
3. Department of Internal Medicine, Hallym University College of Medicine, Chuncheon, Korea.
4. Department of Family Medicine, Seoul National Univeristy College of Medicine, Seoul, Korea.
5. Clinical Research Institute, Seoul National University Hospital, Seoul, Korea.