1. Department of Nephrology and Rheumatology, Georg-August-University Göttingen, 37073 Göttingen, Germany
2. Department of Rheumatology, Johann Wolfgang Goethe-University, Theodor Stern Kay 7, 60590 Frankfurt am Main, Germany
3. Division of Rheumatology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
4. Department of Rheumatology, Southend University Hospital, Westcliff on Sea, Essex SSO-ORY, UK
5. Department of Rheumatology, Medisch Centrum Leeuwarden, 8934 Leeuwarden, The Netherlands
6. Institute of Medical Statistics, Georg-August-University Göttingen, 37073 Göttingen, Germany
7. Medical Centre for Rheumatology Berlin-Buch, 13125 Berlin, Germany