1. Department of Internal Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
2. Department of Internal Medicine, Ewha Womans University School of Medicine, Seoul, Korea.
3. Department of Internal Medicine, Soonchunhyang University College of Medicine, Cheonan, Korea.
4. Department of Internal Medicine, Kyung Hee University School of Medicine, Seoul, Korea.
5. Department of Internal Medicine, Hanyang University College of Medicine, Guri, Korea.