1. Oregon Health & Science University; Portland
2. University of Texas Health Sciences Center; Houston
3. Ghent University Hospital; Ghent Belgium
4. Rheumazentrum Ruhrgebiet; Herne Germany
5. Hospital General de México and Universidad Nacional Autónoma de México; Mexico City Mexico
6. University of Colorado and Denver VA Medical Center; Denver Colorado
7. University of Utah Medical Center; Salt Lake City
8. National Institute of Arthritis and Musculoskeletal and Skin Diseases, NIH; Bethesda Maryland
9. University of California; San Francisco
10. Leiden University Medical Centre; Leiden The Netherlands
11. Diakonhjemmet Hospital; Olso Norway
12. VU University Medical Centre; Amsterdam The Netherlands
13. Toronto Western Hospital and University of Toronto; Toronto, Ontario Canada
14. Alberta Heritage Foundation for Medical Research and University of Alberta; Edmonton, Alberta Canada
15. Seattle Rheumatology Associates; Seattle Washington
16. University of California Davis; Sacramento
17. University of Texas Southwestern Medical Center; Dallas
18. Charité Universitätsmedizin, Campus Benjamin Franklin; Berlin Germany
19. Cedars-Sinai Medical Center; Los Angeles California
20. Academic Medical Centre and University of Amsterdam; Amsterdam The Netherlands