Department of Rheumatology and Clinical Immunology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China. Department of Rheumatology, Affiliated Hospital of Inner Mongolia Medical College, Huhhot, China. Department of Rheumatology, General Hospital of Tianjin Medical University, Tianjin, China. Department of Rheumatology, Beijing Dongfang Hospital, Beijing, China. Department of Rheumatology, Second Hospital of Hebei Medical University, Hebei, China. Department of Rheumatology, Third Hospital of Hebei Medical University, Hebei, China. Department of Rheumatology, First Hospital of Shanxi Medical University, Shanxi, China. Department of Rheumatology, The Bethune International Heping Hospital of Hebei, Hebei, China. Department of Rheumatology, The Affiliated Hospital of QingDao University Medical College, Shandong, China. Formerly National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD, USA.