1. Centre for Prognosis Research, School of Medicine Keele University Staffordshire UK
2. Julius Center for Health Sciences and Primary Care University Medical Center Utrecht Utrecht The Netherlands
3. Centre for Statistics in Medicine, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences University of Oxford Oxford UK
4. NIHR Oxford Biomedical Research Centre John Radcliffe Hospital Oxford UK