1. Health Services Research Unit, Institute of Applied Health Sciences, University of Aberdeen, UK
2. Health Services Research Unit, Institute of Applied Health Sciences, University of Aberdeen, UK, and Health Economics Research Unit, Institute of Applied Health Sciences, University of Aberdeen, UK
3. Health Economics Research Unit, Institute of Applied Health Sciences, University of Aberdeen, UK
4. Department of Medicine and Therapeutics, University of Aberdeen, UK, and Grampian University Hospitals NHS Trust, Aberdeen, UK