1. Department of Internal Medicine, Sungkyunkwan University School of Medicine, Seoul, Korea.
2. Department of Internal Medicine, University of Ulsan College of Medicine, Seoul, Korea.
3. Department of Internal Medicine, Hallym University College of Medicine, Seoul, Korea.
4. Department of Medicine, Yonsei University College of Medicine, Seoul, Korea.
5. Department of Internal Medicine, Ajou University School of Medicine, Suwon, Korea.