1. Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
2. Department of Family Medicine, St. Vincent's Hospital, The Catholic University of Korea College of Medicine, Suwon, Korea.
3. Department of Internal Medicine, Kyung Hee University Hospital at Gangdong, Kyung Hee University College of Medicine, Seoul, Korea.
4. Department of Internal Medicine, Keimyung University Dongsan Medical Center, Daegu, Korea.
5. Department of Internal Medicine, Chungnam National University Hospital, Chungnam National University School of Medicine, Daejeon, Korea.
6. Department of Internal Medicine, Chungbuk National University Hospital, Chungbuk National University College of Medicine, Cheongju, Korea.
7. Department of Internal Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea.