1. Centre for Prognosis Research, Research Institute for Primary Care and Health Sciences; Keele University; Keele UK
2. Department of Biostatistics; Vanderbilt University School of Medicine; Nashville TN
3. Julius Center for Health Sciences and Primary Care; University Medical Center Utrecht; Utrecht The Netherlands
4. Centre for Statistics in Medicine, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences; University of Oxford; Oxford UK