1. Division of Rheumatology, Department of Medicine, The Second Hospital of Shanxi Medical University, Taiyuan, Shanxi 030001, China
2. Department of Medicine, The Second Hospital of Shanxi Medical University, Taiyuan, Shanxi 030001, China
3. Arizona Health Sciences Center, 1501 N. Campbell, Room 4104, P.O. Box 245051, Tucson, AZ 85724, USA
4. University of Washington, 1410 NE Campus Parkway, 459 Schmitz Hall, P.O. Box 355832, Seattle, WA 98195-5832, USA