[1] London Sch Hyg & Trop Med, Dept Hlth Serv Res & Policy, 15-17 Tavistock Pl, London WC1H 9SH, England
[2] Finnish Inst Hlth & Welf, Helsinki, Finland
[3] St Georges Healthcare NHS Trust, St Georges Vasc Inst, London, England
[4] Royal Coll Surgeons England, Clin Effectiveness Unit, London, England
[5] Cambridge Univ Hosp, Cambridge Vasc Unit, NHS Trust, Cambridge, England