1. Department of Internal Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University College of Medicine, Seoul, Korea.
2. Department of Internal Medicine, Kyung Hee University College of Medicine, Seoul, Korea.
3. Department of Internal Medicine, Soonchunhyang University College of Medicine, Cheonan, Korea.
4. Department of Preventive Medicine, Soonchunhyang University College of Medicine, Cheonan, Korea.
5. Department of Internal Medicine, Hanyang University College of Medicine, Guri, Korea.
6. Department of Internal Medicine, The Catholic University of Korea College of Medicine, Seoul, Korea.
7. Department of Internal Medicine, Dankook University College of Medicine, Cheonan, Korea.