Assessing the discrimination of the Kidney Donor Risk Index/Kidney Donor Profile Index scores for allograft failure and estimated glomerular filtration rate in Ireland's National Kidney Transplant Programme

Background: The Kidney Donor Risk Index (KDRI)/Kidney Donor Profile Index (KDPI) is relied upon for donor organ allocation in the USA, based on its association with graft failure in time-to-event models. However, the KDRI/KDPI has not been extensively evaluated in terms of predictive metrics for graft failure and allograft estimated glomerular filtration rate (eGFR) outside of the USA.

Methods: We performed a retrospective analysis of outcomes in the Irish National Kidney Transplant Service Registry for the years 2006-13. Associations of the KDRI/KDPI score with eGFR at various time points over the follow-up and ultimate graft failure were modelled.

Results: A total of 772 patients had complete data regarding KDRI/KDPI calculation and 148 of these allografts failed over the follow-up. The median and 25-75th centile for KDRI/KDPI was 51 (26-75). On repeated-measures analysis with linear mixed effects models, the KDRI/KDPI (fixed effect covariate) associated with eGFR over 5 years: eGFR = -0.25 (standard error 0.02; P < 0.001). The variability in eGFR mathematically accounted for by the KDRI/KDPI score was only 21%. The KDRI/KDPI score did not add significantly to graft failure prediction above donor age alone (categorized as > and <50 years of age) when assessed by the categorical net reclassification index.

Conclusions: In this cohort, while the KDRI/KDPI was predictive of eGFR over the follow-up, it did not provide additive discrimination above donor age alone in terms of graft failure prediction. Therefore it is unlikely to help inform decisions regarding kidney organ allocation in Ireland.