[1] Univ Cambridge, Dept Surg, Addenbrookes Hosp, Cambridge CB2 0QQ, England
[2] Addenbrookes Hosp, Tissue Typing Lab, Cambridge, England
[3] Inst Publ Hlth, MRC Biostat Unit, Cambridge, England
[4] Univ Cambridge, Dept Renal Med, Addenbrookes Hosp, Cambridge CB2 0QQ, England