Background: CPRA, which is used for deceased donor (DD) kidney (KI) and pancreas/kidney-pancreas (PA/KP) allocation, is computed with KI DD HLA and ethnic frequencies. CPRA values are calculated in each of four ethnic groups using unacceptable antigens (UAs) reported for candidates. These are combined into an overall CPRA value using weights based on the ethnic distribution of KI DD for 2007-2008.

Data and Methods: This study investigated how differences in ethnic weights affect CPRA value by comparing KI CPRA (using KI DD ethnic weights) vs. heart (HR) CPRA (using HR DD ethnic weights) for all HR registrations ever on the waiting list during 1/1/11-6/30/14. Analysis was based on OPTN data using the most recent UAs reported for a registration, and was limited to those with any UAs (N=2,965).

Results: The ethnic distribution of HR DDs was significantly different from KI DDs (2007-2008 donors): 63.5 vs 68.7 for Caucasians; 16.3 vs 14.7 for African Americans; 18.5 vs 14.3 for Hispanics; 1.7 vs 2.3% for Asians. The KI and HR CPRA values were very similar (Figure 1), with identical values for 2,119 (71.5%) registrations – a difference of 1% point for 837 (28.2%) and a difference of 2% points for 9 (0.3%). For registrations with a difference, KI CPRA > HR CPRA in approximately 2/3.

While the differences are relatively small, 82 registrations (2.8%) would be in a different CPRA group based on the KI CPRA if a sliding CPRA scale were used for HR allocation consistent with the one used for KI allocation since 12/4/14. Of these 82 registrations, 64 would have been in a lower CPRA group using HR CPRA.

Conclusions: Despite significant differences in ethnic distribution of HR and KI DDs, HR and KI CPRA values are very similar. If CPRA were computed for heart candidates on the waiting list, it may be beneficial to use the existing KI/PA/KP CPRA formula to avoid confusion within the transplant community and potential differences in values for registrations waiting for both HR and KI.

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