1. Maastricht University; Maastricht The Netherlands
2. Leiden University Medical Center; Leiden the Netherlands
3. Sint Laurentius Hospital Roermond and Sint Jans Gasthuis Weert; Roermond and Weert The Netherlands
4. Erasmus Medical Center Rotterdam; Rotterdam The Netherlands
5. University of Groningen; University Medical Center Groningen, and Medical Center Leeuwarden; Leeuwarden The Netherlands
6. University of British Columbia, Vancouver, Canada; and Arthritis Research Centre of Canada; British Columbia Canada
7. Institute for Work & Health and University of Toronto; Toronto Canada
8. Amsterdam Medical Center; Amsterdam The Netherlands