Associations Among Circle-Based Kidney Allocation, Center Waiting Time, and Likelihood of Deceased-Donor Kidney Transplantation

Abstract

Rationale & Objective

The kidney allocation system (KAS250), using circle-based distribution, attempts to address geographic disparities through broader sharing of deceased-donor kidney allografts. This study evaluated the association between KAS250 and likelihood of deceased-donor kidney transplantation (DDKT) among wait-listed candidates, and whether the policy has differentially affected centers with shorter versus longer waiting time.

Study Design

Retrospective cohort study.

Setting & Participants

160,941 candidates waitlisted at 176 transplant centers between March 2017 and March 2024.

Exposure

KAS250 allocation policy.

Outcome

Rate of DDKT.

Analytical Approach

Multivariable Cox regression, modeling KAS250 as a time-dependent variable.

Results

KAS250 was not independently associated with likelihood of DDKT overall (HR, 1.01 vs pre-KAS250 [95% CI, 0.97-1.04]). KAS250’s association with likelihood of DDKT varied across centers from HR, 0.18 (DDKT less likely after KAS250), to HR, 17.12 (DDKT more likely) and varied even among neighboring centers. KAS250 was associated with decreased DDKT at 25.6% and increased DDKT at 18.2% of centers. Centers with previously long median waiting times (57+ months) experienced increased likelihood of DDKT after KAS250 (HR, 1.20 [95% CI, 1.15-1.26]) whereas centers with previously short median waiting times (6-24 months; HR, 0.88 [95% CI, 0.84-0.92]) experienced decreased likelihood of DDKT.

Limitations

Retrospective study of allocation policy changes, confounded by multiple changes over the study time frame.

Conclusions

Association between KAS250 and DDKT varied across centers. For 1 in 4 centers, DDKT was less likely after KAS250 relative to pre-KAS250 trends. Candidates at centers with previously long waiting times experienced an increased likelihood of DDKT after KAS250. Thus, broader distribution of kidneys may be associated with improved equity in access to DDKT, but additional strategies may be needed to minimize disparities between centers.

Plain-Language Summary

This study examines how a recent policy change, KAS250, aimed at broadening the geographic sharing of deceased-donor kidneys, has impacted likelihood of kidney transplantation in the United States. Historically, kidney allocation occurred within local geographic boundaries, leading to unequal rates of transplantation across regions. KAS250, implemented in March 2021, replaced this system with a broader allocation radius of 250 miles around the donor hospital. Using national registry data, the study found that while there was no overall significant increase in the likelihood of transplantation nationally under KAS250, the policy’s effect varied widely even among neighboring transplant centers. One quarter of centers experienced a decrease in the likelihood of DDKT after KAS250. In contrast, centers with longer pre-KAS250 waiting times experienced an increased likelihood of transplantation, suggesting some success in reducing disparities between centers. Ongoing surveillance will be needed to ensure KAS250 is meeting the intended aim of more equitably distributing organs.