The new kidney allocation system (KAS) has increased transplant rates for highly sensitized candidates. We hypothesized that increasing unacceptable antigens to transition candidates from 80-98% CPRA categories into the regional share 99% CPRA and national share 100% CPRA categories would increase the donor pool size and the opportunities for transplantation.

Kidney transplant data stratified by CPRA were analyzed during 3 time-periods: Prior to KAS (1/1/2014-12/31/2014); Post KAS1 using CDC crossmatch level HLA antibodies for unacceptable antigens (1/1/2015-4/30/2015) and Post-KAS2 using CDC and flow cytometric crossmatch level HLA antibodies to define unacceptable antigens (5/1/2015-12/1/2015).

Transplant rates were similar in the Pre-KAS and the Post-KAS1 period when using CDC crossmatch level HLA antibodies for determining unacceptable antigens. However, reducing this threshold and increasing unacceptable antigens for sensitized candidates increased transplants from 7 during Post-KAS1 (5 mo. period) to 42 during Post-KAS2 (6 mo. period). The number of transplants for 1-79% CPRA candidates increased from 6 to 12, for the 80%-98% CPRA candidates the increase was from 1 to 7, and the largest increase was for 100% CPRA candidates from 0 to 23. No transplants occurred within the 99% CPRA category during any Post-KAS period despite increasing the potential donor pool size with regional share policies. This disadvantage for 99% CPRA candidates was also observed in the 6 month National KAS Report; transplant rates for 100% CPRA candidates increased ten-fold ( 1.0 to 11.2%) compared to the three-fold (1.3% to 3.7%) increase for 99% CPRA candidates. This disadvantage likely arises from competition between 99% and 100% CPRA candidates for donors with unique HLA phenotypes. Compatible donors for 99% CPRA candidates are infrequent and are likely allocated to 100% CPRA candidates at the local, regional, and national levels before becoming available to 99% CPRA candidates at the regional level.

Additional CPRA allocation points increase transplant opportunities for 1-98% CPRA candidates within the local donor pool and transitioning candidates into the 100% CPRA category allows access to a larger national donor pool. However, candidates with 99% CPRAs may be disadvantaged if the size of the local and regional donor pools is insufficient for finding compatible donors.

CITATION INFORMATION: Houp J, Vega R, Lonze B, Desai N, Montgomery R, Jackson A. Optimizing CPRAs for Sensitized Kidney Waitlist Candidates: The Devil Is in the KAS Details. Am J Transplant. 2016;16 (suppl 3).

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