Center Geography or Center Practice? Decomposing Geographic Variation in Access to Kidney Transplantation Before...

Before KAS250 (circles-based allocation), donor service area (DSA) of listing was the largest contributor to deceased donor kidney transplantation (DDKT) rate disparities. Both before and after KAS250, it is unclear to what extent DSA-level disparities are attributable to center-level practice variation. We aimed to disentangle contributions to DDKT rate variation from: (1) center practices, (2) kidney distribution within sharp policy boundaries (DSAs, OPTN Regions), and (3) other geographic variation in kidney scarcity.

With national transplant registry data, we studied transplant rate variation in the pre-KAS250 era, which prioritized patients based on DSAs and Regions, and under KAS250, which prioritizes patients within 250 nautical mile circles. We modeled candidate DDKT rates with multilevel Poisson regression, adjusting for candidate factors, and calculated median incidence rate ratios (MIRR) to summarize variation attributable to DSAs, OPTN regions, states, census divisions, and to centers within those units.

DSA-level MIRR declined sharply from _1.311.35_1.39 to _1.131.17_1.21 after KAS250 implementation. Under KAS250, 93.4% of geographic variability in transplant rates was attributable to center-level (within-DSA) variation (MIRR: centers _1.761.82_1.86, DSAs _1.131.17_1.21), while before KAS250, only 81.7% of geographic variability in transplant rates was attributable to center-level (within-DSA) variation (MIRR: centers _1.831.89_1.95, DSAs _1.311.35_1.39). Adjusted center-level DDKT rates under KAS250 were highly associated with offer acceptance rates (ρ = 0.60, p < 0.001).

Though geographic disparities are driven primarily by center-level practice differences including offer acceptance, KAS250 did reduce DSA-level disparities. Further allocation policy changes are unlikely to substantially reduce geographic variation in DDKT rates.