1 Centre for Prognosis Research, Research Institute for Primary Care and Health Sciences, Keele University, Keele, Staffordshire, ST5 5BG, UK r.riley@keele.ac.uk.
2 Contributed equally.
3 Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands.
4 Cochrane Netherlands, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands.
5 Centre for Prognosis Research, Research Institute for Primary Care and Health Sciences, Keele University, Keele, Staffordshire, ST5 5BG, UK.
6 Centre for Statistics in Medicine, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UK.
7 Centre for Clinical Research, Halifax, Nova Scotia, Canada.