1. Department of Internal Medicine, Chung-Ang University College of Medicine, Seoul, Korea.
2. Department of Internal Medicine, Sungkyunkwan University School of Medicine, Seoul, Korea.
3. Department of Internal Medicine, Inje University College of Medicine, Seoul, Korea.
4. Department of Internal Medicine, University of Ulsan College of Medicine, Seoul, Korea.
5. Department of Internal Medicine, The Catholic University of Korea College of Medicine, Seoul, Korea.
6. Department of Internal Medicine, Ewha Womans University School of Medicine, Seoul, Korea.
7. Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea.
8. Department of Medicine, Korea University Graduate School, Seoul, Korea.