Matching Graft Life Expectancy with Patient Life Expectancy

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Abstract

Introduction

One of the key recommendations following a review of the current UK Kidney Allocation Scheme was to match graft life expectancy with patient life expectancy more effectively in order to maximise the lifetime of kidneys transplanted and reduce the incidence of offer declines.

Material and Methods

Data from the UK Transplant Registry held by NHS Blood and Transplant on 7,628 first adult kidney only recipients of adult deceased donor kidney transplants in the UK 2006-2012 were analysed. Donor factors potentially influencing graft outcome and recipient factors potentially influencing graft and patient outcomes were investigated using Cox regression. A Kidney Donor Risk Index (DRI) and a Kidney Recipient Risk Index (RRI) were derived from the models and validated on an independent dataset. Both indices were divided into quartiles and the combinations of the four donor and four recipient quartiles were used to investigate offer decline rates and post-transplant survival.

Results and Discussions

Donor factors found to significantly predict poor graft outcome included; older age, shorter height, a history of hypertension, positive CMV result, longer hospital stay before death, lower eGFR at time of offering and male donors. Recipient factors found to significantly predict poor transplant outcome (time to graft failure or death) included; older age, on dialysis at point of registration, diabetic and longer time on dialysis. A DRI based on the 7 significant factors and a RRI based on the 4 significant factors were derived and confirmed to be prognostic of outcome in a validation cohort (concordance statistic 0.64 for both models). Using the combination of the DRI and RRI quartiles it was observed that the poorest donors with the best recipients had the highest offer decline rate (64%) and the best donors with the best recipients had the lowest offer decline rate (23%). For kidneys transplanted from the best donors into the best recipients, 15-year patient survival was 86% compared with 70% graft survival, suggesting that patients are likely to outlive their grafts. Conversely, for the best donors with the poorest recipients, patient survival was 37% compared with 73% graft survival, suggesting that patients are likely to die with a functioning graft (Figure 1). These extreme examples demonstrate the importance of matching graft and patient life expectancies.

Conclusions

A Kidney Donor Risk Index alongside a Kidney Recipient Risk Index provides a clinically useful tool that can be used in allocation schemes to maximise the lifetime of kidneys transplanted and reduce the incidence of offer declines.

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