1. Department of Internal Medicine, Seoul Metropolitan Government-Seoul National University Boramae Medical Center, Seoul, Korea.
2. Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
3. Department of Internal Medicine, Chonbuk National University Medical School, Jeonju, Korea.
4. Department of Internal Medicine, Inje University College of Medicine, Busan, Korea.
5. Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, Korea.
6. Department of Internal Medicine, Pohang St. Mary's Hospital, Pohang, Korea.