1. Division of Rheumatology, Department of Medicine, National Medical Center, Seoul, Korea.
2. Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
3. Division of Rheumatology, Department of Medicine, Yonsei University College of Medicine, Seoul, Korea.
4. Department of Rheumatology, Hanyang University Hospital for Rheumatic Diseases, Seoul, Korea.
5. Division of Rheumatology, Department of Internal Medicine, Gachon University College of Medicine Gil Medical Center, Incheon, Korea.
6. Division of Rheumatology, Department of Internal Medicine, Ewha Womans University College of Medicine, Seoul, Korea.