1. Clinic of Internal Medicine III, Department of Oncology, Haematology, Rheumatology and Clinical Immunology, University Hospital Bonn , Bonn, Germany
2. Department of Rheumatology, Medical University of Graz , Graz, Austria
3. Department of Rheumatology, Hospital of Bruneck (ASAA-SABES), Teaching Hospital of the Paracelsus Medical University , Bruneck, Italy
4. Institute of Medical Biometry, Informatics and Epidemiology, University Hospital Bonn , Bonn, Germany