1. Department of Health Services Research and Policy, London School of Hygiene and Tropical Medicine, United Kingdom (K.H., D.A.C.).
2. Clinical Effectiveness Unit, the Royal College of Surgeons of England, London, United Kingdom (K.H., A.S.J., S.W., D.A.C.).
3. Southmead Hospital, North Bristol National Health Service Trust, United Kingdom (D.C.M.).
4. St. George’s Vascular Institute, St. George’s Healthcare National Health Service Trust, London, United Kingdom (I.M.L.).