1. Department of Medicine 1, Holbæk Hospital , DK-4300 Holbæk , Denmark
2. OPEN—Open Patient Data Explorative Network, Department of Clinical Research, University of Southern Denmark and Odense University Hospital , DK-5000 Odense , Denmark
3. NDORMS, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Oxford University Hospitals , Oxford OX3 7LD , UK