[1] Royal Coll Surgeons England, Clin Effectiveness Unit, London WC2A 3PN, England
[2] Harefield Hosp, Harefield, Middx, England
[3] NHS Blood & Transplant, Bristol, Avon, England
[4] Papworth Hosp, Papworth Everard, Cambs, England
[5] Freeman Rd Hosp, Newcastle Upon Tyne, Tyne & Wear, England