KAS Turns Four: The State of Deceased Donor Kidney Allocation in the U.S.

Abstract

Background: This study examines very recent trends in deceased donor kidney transplantation to assess the performance of the kidney allocation system (KAS), implemented December 4, 2014, and whether bolus effects associated with KAS have stabilized nearly four years after implementation. Methods: The overall number of deceased donor kidney transplants, as well as the proportion of transplants by recipient and transplant characteristics, were calculated monthly from December 2013 through September 2018 and examined graphically. Kidney discard rates – the percentage of kidneys recovered for transplant not transplanted – were analyzed overall and stratified by donor Kidney Donor Profile Index (KDPI). Delayed graft function (DGF) was defined as the recipient requiring dialysis within one week of transplant; monthly rates were examined graphically. We also surveyed other published research to round out our assessment of KAS’s impact. Results: Marked bolus effects, particularly a sharp increase in transplants to highly sensitized and high dialysis time recipients, were associated with KAS implementation but have since stabilized. Transplant access has improved for African American candidates, who now receive a proportion of transplants comparable to their representation on the waiting list. Subtype-compatible (“A2/A2B to B”) transplants have increased sharply but are still numerically small (~20/month) and may have plateaued. Though the overall kidney discard rate has not changed appreciably over the past five years, the rate for KDPI 35-85% kidneys has trended slightly downward since 2017. After initially rising with KAS, DGF rates have tapered but still remain slightly above pre-KAS levels. One-year graft and patient survival remain excellent. Conclusions: The number of deceased donor kidney transplants has reached an all-time high and continues to rise, a boon for the nearly 100,000 patients with kidney failure on the waiting list. Several key bolus effects that were anticipated with KAS did indeed materialize, drastically changing the characteristics of the initial wave of post-KAS recipients. These bolus effects have since tapered, suggesting KAS has, by and large, reached a steady state. KAS has improved equity across ethnicities and levels of sensitization but did not attempt to resolve geographic inequities. Published research has confirmed that substantial geographic disparities remain. The goal of increasing utilization of kidneys at high risk of discard has not been met. Numerous policy changes and system improvement initiatives have been proposed, many of which are currently underway or pending implementation, to improve organ utilization.