1. Department of Rheumatology, VU University Medical Center
2. Department of Rheumatology, Amsterdam Medical Center
3. Department of Clinical Chemistry, VU University Medical Center
4. Reade, Amsterdam
5. Department of Rheumatology, Maartenskliniek, Woerden
6. Department of Epidemiology and Biostatistics
7. Department of Radiology and Nuclear Medicine, VU University Medical Center, Amsterdam, The Netherlands