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Abstract: PO2061

A Geospatial Method to Improve Sociodemographic Characterization of Transplant Referral Regions

Session Information

Category: Transplantation

  • 1902 Transplantation: Clinical


  • Schappe, Tyler, Duke University, Durham, North Carolina, United States
  • Peskoe, Sarah B., Duke University, Durham, North Carolina, United States
  • Pendergast, Jane F., Duke University, Durham, North Carolina, United States
  • Wang, Virginia, Duke University, Durham, North Carolina, United States
  • Boulware, L. Ebony, Duke University, Durham, North Carolina, United States
  • McElroy, Lisa M., Duke University, Durham, North Carolina, United States

Progress towards health equity in kidney transplant requires robust characterization of transplant center referral populations. Transplant referral regions (TRRs) define geographic catchment areas for transplant centers in the United States and have previously been linked to sociodemographic data using ZIP codes. We compared a spatial intersection method to a ZIP code crosswalk method of linking sociodemographic data to TRRs.


A spatial intersection method was used to assign census block groups to TRRs based on area of intersection. We compared the spatial congruence of the spatial intersection and ZIP code crosswalk methods by calculating the number of census block groups assigned to more than one TRR and calculating the total area assigned to the incorrect TRR.


We defined 105 TRRs for 238 transplant centers (figure 1a). The ZIP code crosswalk method resulted in 4,627 census block groups being included in more than one TRR, while the spatial intersection method eliminated this problem. The spatial method resulted in a mean and median reduction in misassigned area of 65% and 83% across all TRRs, respectively, compared to the ZIP code crosswalk method (figure 1b).


Characterizing TRRs with census block groups increases spatial resolution, and provides more balanced population counts. Our spatial approach avoids errors due to duplicative assignments and allows more accurate characterization of referral population sociodemographics. This approach can enrich transplant center knowledge of local referral populations, assist researchers in understanding the influence of social determinants of health on access to transplant, and inform interventions to improve heath equity.

Figure 1A. National Kidney transplant referral regions (TRRs). Figure 1B. Left: Census block groups colored by TRR in North Carolina. Right: Spatial congruence between census block group boundaries and derived TRR boundaries; bold lines show misassigned area.


  • Other NIH Support