1. Division of Rheumatology, Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, Korea.
2. Division of Rheumatology, Department of Internal Medicine, Busan Medical Center, Busan, Korea.
3. Division of Rheumatology, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea.
4. Division of Rheumatology, Department of Internal Medicine, Chung-Ang University College of Medicine, Seoul, Korea.