[1] Royal Coll Surgeons England, Clin Effectiveness Unit, 35-43 Lincolns Inn Fields, London WC2A3PE, England
[2] St Georges Univ Hosp NHS Fdn Trust Vasc Inst, London, England
[3] London Sch Hyg & Trop Med, Dept Hlth Serv Res & Policy, London, England
[4] Cambridge Univ Hosp NHS Fdn Trust, Div Vasc & Endovasc Surg, Addenbrookes Hosp, Cambridge, England