*Purpose: Implementation of the kidney allocation system in 2014 greatly reduced access disparity due to HLA sensitization. To address persistent disparities among both candidate cPRA and ABO blood groups, we propose a unified cPRA metric which simultaneously considers the impact of candidate HLA and ABO sensitization on the same scale.

*Methods: An ethnic-weighted ABO-adjusted cPRA value was computed, incrementing the HLA cPRA by the remaining fraction of HLA-compatible donors that are ABO-incompatible. For example, a patient with HLA-A2 antibody who is blood group O would have an HLA cPRA of 45.9%, but based on A+B+AB phenotype frequencies 52.6% of HLA-compatible donors are ABO-incompatible, giving a unified cPRA of 74.3%. (Calculator available at http://transplanttoolbox.org/abo_hla_cpra).

*Results: Consideration of ABO sensitization resulted in a higher unified cPRA relative to HLA cPRA, except for AB candidates who are not ABO-sensitized. Plotting 148,520 candidate waitlistings from post-KAS until June 30, 2017, we observed widely variable impacts (Fig 1), with the largest absolute increase in cPRA for blood group O candidates who were not HLA-sensitized. Capturing the variable impact of candidate ABO could more equitably determine allocation points, especially for highly sensitized candidates near point group boundaries. Within HLA cPRA Point Group 99, overall 44% of candidates would move up to ABO-adjusted cPRA Point Group 100, though this proportion varied substantially by candidate ABO blood group (Fig 2). Nearly all O candidates would move up, along with most B candidates, but relatively few A candidates.

*Conclusions: ABO-adjusted cPRA measures the proportion of immune-compatible donors more accurately than conventional HLA cPRA alone. This tool might enable development of allocation policies that would allow for more ABO-compatible transplants and improve equity for candidates currently disadvantaged by both HLA sensitization and their ABO blood group.

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