1. Department of Internal Medicine, Gil Medical Center, Gachon University College of Medicine, Incheon, Korea.
2. Department of Internal Medicine, Inha University School of Medicine, Incheon, Korea.
3. Department of Internal Medicine, International St. Mary's Hospital, Catholic Kwandong University College of Medicine, Incheon, Korea.
4. Department of Internal Medicine, Cheju Halla General Hospital, Jeju, Korea.
5. Department of Internal Medicine, Ewha Womans University School of Medicine, Seoul, Korea.