1. Health Economics Research Unit, Aberdeen, UK
2. Health Services Research Unit, Aberdeen, UK
3. Division of Applied Medicine, University of Aberdeen, Aberdeen, UK
4. Royal Devon and Exeter Hospital and University of Exeter Medical School, Exeter, UK
5. Vascular Surgery, Vascular Laboratory, St James's University Hospital, Leeds, UK
6. School of Medicine, Medical and Biological Sciences, University of St Andrews, St Andrews, UK