1. Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea.
2. Department of Internal Medicine, Seoul National University, Seoul, Korea.
3. Medical Research Collaborating Center, Seoul National University Hospital and Seoul National University College of Medicine, Seoul, Korea.
4. Department of Internal Medicine, Chonnam National University Medical School, Gwangju, Korea.
5. Department of Internal Medicine, Inje University, Pusan Paik Hospital, Busan, Korea.
6. Department of Internal Medicine, Eulji Medical Center, Eulji University, Seoul, Korea.