Using Geographic Catchment Areas to Measure Population-based Access to Kidney Transplant in the United States.

Background. Monitoring efforts to improve access to transplantation requires a definition of the population attributable to a transplant center. Previously, assessment of variation in transplant care has focused on differences between administrative units-such as states-rather than units derived from observed care patterns. We defined catchment areas (transplant referral regions [TRRs]) from transplant center care patterns for population-based assessment of transplant access. Methods. We used US adult transplant listings (2006-2016) and Dartmouth Atlas catchment areas to assess the optimal method of defining TRRs. We used US Renal Data System and Scientific Registry of Transplant Recipient data to compare waitlist- and population-based kidney transplant rates. Results. We identified 110 kidney, 67 liver, 85 pancreas, 68 heart, and 43 lung TRRs. Most patients were listed in their assigned TRR (kidney: 76%; liver: 75%; pancreas: 75%; heart: 74%; lung: 72%), although the proportion varied by organ (interquartile range for kidney, 65.7%-82.5%; liver, 58.2%-78.8%; pancreas, 58.4%-81.1%; heart, 63.1%-80.9%; lung, 61.6%-76.3%). Patterns of population- and waitlist-based kidney transplant rates differed, most notably in the Northeast and Midwest. Conclusions. Patterns of TRR-based kidney transplant rates differ from waitlist-based rates, indicating that current metrics may not reflect transplant access in the broader population. TRRs define populations served by transplant centers and could enable future studies of how transplant centers can improve access for patients in their communities.