1. Departments of Epidemiology, Biostatistics and Health Technology Assessment; Radboud University Nijmegen Medical Centre; Nijmegen; The Netherlands
2. Centre for Health Sciences, Barts and the London School of Medicine and Dentistry, Queen Mary; University of London; U.K.
3. Scientific Institute for Quality of Healthcare; Radboud University Nijmegen Medical Centre; Nijmegen; The Netherlands