Retroactive application of the new kidney allocation system to renal transplants performed in the ECD/SCD era

The kidney allocation system (KAS) aims to improve deceased donor kidney transplant outcomes by matching of donor allografts and kidney recipients using the kidney donor risk index (KDRI) and recipient estimated post-transplant survival (EPTS) indices. In this single-center study, KAS was retroactively applied to 573 adult deceased donor kidney transplants (2004-2012) performed in the extended criteria/standard criteria donor (ECD/SCD) era. Donor KDRI and recipient EPTS were calculated, and transplants were analyzed to identify KAS fits. These were defined as allocation of top 20% allografts to top 20% recipients and bottom 80% allografts to bottom 80% recipients. On retroactive calculation, 70.2% of all transplants fit the KAS. Transplants that fit the KAS had inferior 1- and 5-yr patient survival (95.5% vs. 98.8%, p = 0.048, and 83.4% vs. 91.7%, p = 0.018) and similar 1- and 5-yr graft survival compared to transplants that did not fit the KAS (91.3% vs. 94.1%, p = 0.276, and 72.7% vs. 73.9%, p = 0.561). While EPTS correlated with recipient survival (HR = 2.96, p < 0.001), KDRI correlated with both recipient (HR = 3.56, p < 0.001) and graft survival (HR = 3.23, p < 0.001). Overall, retroactive application of the KAS to transplants performed in the ECD/SCD era did not identify superior patient survival for kidneys allocated in accordance with the KAS.