Multiple reviews of machine perfusion find reduced delayed function of kidneys but no effect on graft survival
A group from Sun Yat-sen University, Guangzhou, China has recently published a systematic review comparing the outcomes in patients receiving kidneys from donation after cardiac death (DCD). Deng et al conducted a meta-analysis using the results from four randomised controlled trials (351 kidneys). Machine perfusion reduced the rate of delayed graft function compared to static cold storage (odds ratio=0.56, p=0.008).
Another group, from the University of Sydney, Australia, Lam et al, published a review late last year, including DCD and (donation after brain-death) DBD kidneys (1353 kidneys), also finding a reduced risk of delayed graft function (relative risk=0.83, p=0.01).
Our group has recently conducted a systematic review and meta-analysis addressing the same issue, presented at the Transplantation Society Congress, Berlin 2012, and now published in the British Journal of Surgery. We conducted a meta-analysis including all donor types (1475 kidneys) as well as subgroup analysis by donor type (DCD versus heart-beating donation or DBD). Whilst in the overall meta-analysis of all donor types we found a significant reduction in delayed function with machine perfusion (relative risk=0.81, p=0.002) we did not find a significant reduction with kidneys from cardiac death alone (relative risk=0.8, p=0.094). This could be due to two key factors:
1) We did not include data from the study by Matsuno et al, as we felt it was not a randomised controlled trial. It is relatively small however, and may not have contributed greatly to the overall meta-analysis by Deng et al.
2) I-squared testing showed heterogeneity of 40%, we therefore used random effects meta-analysis, which will result in wider confidence intervals. Deng et al used fixed effects meta-analysis given the lower heterogeneity between their included studies.
Both of these factors will result in less power to demonstrate a significant effect in our subgroup analysis of DCD kidneys. Overall though the effect of machine perfusion was similar on DBD and DCD in our study. Overall we would agree with the conclusions of Deng et al.
In comparison to the study by Lam et al, our results are very similar, including the point estimate of the summary effect and the 95% confidence intervals. (relative risk=0.83, 0.72-0.96 and relative risk=0.81, 0.71-0.92). These slight differences can be attributed to two small differences between the studies:
1) We were fortunate to receive extra information from the steering committee of the Eurotransplant study, which allowed us to incorporate results from the study extensions of DCD, ECD, and senior program kidneys without overlap.
2) We did not include data from the paper by Jaffers and Banowsky 1989, as we felt it was a retrospective study and did not meet our inclusion criteria. We instead included a study by Van der Vliet et al.
These slight differences in methods lead to the small differences in summary effects and confidence intervals. Overall we would agree with the conclusions of Lam et al.
Interestingly all three reviews did not find evidence for a difference in graft survival, Deng et al and Lam et al using meta-analysis, and our group in narrative review. Further weight is added to this discussion by the recent review of UNOS data by Cannon et al at the University of Louisville, USA. Across multivariate analysis, paired kidney analysis, and propensity-matched comparisons, Cannon et al found a consistent reduction in delayed function associated with machine perfusion, but no difference in graft survival.
