Effect of donor age and cold storage time on outcome in recipients of kidneys donated after circulatory death in the UK: a cohort study

Background Use of kidneys donated after controlled circulatory death has increased the number of transplants undertaken in the UK but there remains reluctance to use kidneys from older circulatory-death donors and concern that kidneys from circulatory-death donors are particularly susceptible to cold ischaemic injury. We aimed to compare the effect of donor age and cold ischaemic time on transplant outcome in kidneys donated after circulatory death versus brain death. Methods We used the UK transplant registry to select a cohort of first-time recipients (aged >= 18 years) of deceaseddonor kidneys for transplantations done between Jan 1, 2005, and Nov 1, 2010. We did univariate comparisons of transplants from brain-death donors versus circulatory-death donors with chi(2) tests for categorical data and Wilcoxon tests for non-parametric continuous data. We used Kaplan-Meier curves to show graft survival. We used Cox proportional hazards regression to adjust for donor and recipient factors associated with graft-survival with tests for interaction effects to establish the relative effect of donor age and cold ischaemia on kidneys from circulatory-death and brain-death donors. Findings 6490 deceased-donor kidney transplants were done at 23 centres. 3 year graft survival showed no difference between circulatory-death (n=1768) and brain-death (n=4127) groups (HR 1.14, 95% CI 0.95-1.36, p=0.16). Donor age older than 60 years (compared with <40 years) was associated with an increased risk of graft loss for all deceaseddonor kidneys (2.35, 1.85-3.00, p<0.0001) but there was no increased risk of graft loss for circulatory-death donors older than 60 years compared with brain-death donors in the same age group (p=0.30). Prolonged cold ischaemic time (>24 h vs <12 h) was not associated with decreased graft survival for all deceased-donor kidneys but was associated with poorer graft survival for kidneys from circulatory-death donors than for those from brain-death donors (2.36, 1.39-4.02, p for interaction=0.004). Interpretation Kidneys from older circulatory-death donors have equivalent graft survival to kidneys from brain-death donors in the same age group, and are acceptable for transplantation. However, circulatory-death donor kidneys tolerate cold storage less well than do brain-death donor kidneys and this finding should be considered when developing organ allocation policy.