1. Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
2. Department of Internal Medicine, Seoul St. Mary's Hospital, Catholic University of Korea, Seoul, Korea.
3. Department of Internal Medicine, Kyung Hee University School of Medicine, Seoul, Korea.
4. Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea.
5. Department of Internal Medicine, Hanyang University College of Medicine, Seoul, Korea.
6. Department of Internal Medicine, Ewha Womans University, Seoul, Korea.
7. Department of Internal Medicine, College of Medicine, Chungbuk National University, Cheongju, Korea.