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Clarification of CPRA calculation value and display

Clarification of CPRA calculation value and display


Kidney and pancreas transplant program staff, KPD system users, Histocompatibility lab staff and supervisors


Members have contacted us with questions about the detailed CPRA (calculated panel reactive antibody) value versus the CPRA score used for allocation.  We wanted to clarify how the two scores displayed. The detailed score and CPRA score used for allocation are both found on the match run in DonorNet SM, view and edit candidate pages in Waitlist SM, the CPRA calculator in Waitlist SM and on the OPTN website.

About the CPRA calculation and value

The CPRA calculator uses a transplant candidate’s unacceptable antigens to estimate the compatibility of donors with the candidate. When a candidate’s antibodies are entered into the calculator, this is how we display the results.

First, we take the CPRA value from the calculation, which is always a decimal value less than 1 (for example, 0.97498). This is the value we store in our system.

Next, we round to the nearest hundredth, per OPTN policy (.97). Results are calculated up to 15 decimal places but we show only the first two decimal places.

Finally, we multiply by 100 to turn the result into a percentage (97%). The match run uses this value.

0.236670273731295 – this is a CPRA of 24% (round to 100th, the 6 rounds the 3 to a 4, then we multiply by 100 to express as a whole number)

0.97763526937871 – 98%


If you have questions about OPTN policy, please contact [email protected]. For UNetSM system questions, contact UNOS customer service at [email protected] or (800) 978-4334.

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