1. University of Leeds, Leeds, UK; and University of Oxford; Oxford UK
2. St. Vincent's University Hospital and University College Dublin; Dublin Ireland
3. Brigham and Women's Hospital; Harvard Medical School; Boston Massachusetts
4. Medical University of Vienna; Vienna Austria
5. Academic Medical Center/University of Amsterdam; Amsterdam The Netherlands
6. Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) , Oslo, Norway; and People with Arthritis/Rheumatism in Europe; Zurich Switzerland
7. Geneva University Hospital and Geneva University; Geneva Switzerland
8. University of Utah; Salt Lake City
9. GRAPPA and Toronto Western Hospital; University Health Network; Toronto Ontario Canada
10. VU University Medical Centre and EMGO Research Institute; Amsterdam The Netherlands
11. University of Toronto and Toronto Western Hospital; University Health Network; Toronto Ontario Canada
12. New York Medical College; Valhalla New York
13. GRAPPA; Bath UK
14. University of California at San Diego
15. Copenhagen University Hospital; Copenhagen Denmark
16. Diakonhjemmet Hospital; Oslo Norway
17. University Hospital Münster; Münster Germany
18. University of Bath; Bath UK
19. St. Joseph Health System; University of Washington; Seattle
20. University of Queensland; Brisbane Queensland Australia
21. University of Pennsylvania; Philadelphia
22. Stanford University; Palo Alto California
23. Royal National Hospital for Rheumatic Diseases and University of Bath; Bath UK
24. University of Leeds; Leeds UK