[1] Royal Coll Surgeons England, Clin Effectiveness Unit, London WC2A 3PN, England
[2] Univ Bristol, Clin Trials & Evaluat Unit, Bristol, Avon, England
[3] NHS Blood & Transplant, Bristol, Avon, England
[4] Papworth Hosp NHS Fdn Trust, Cambridge, England
[5] Freeman Rd Hosp, Newcastle Upon Tyne, Tyne & Wear, England
[6] Univ Birmingham, Queen Elizabeth Hosp, Birmingham B15 2TH, W Midlands, England