Degree of sensitization in kidney transplant candidates ranges from calculated PRA (CPRA) 0%-100%, depending on the proportion of the donor pool against whom the candidate has HLA antibodies. Wait-list mortality is higher and compatible donors more difficult to find for highly sensitized candidates, who are thus awarded 4 priority points towards organ allocation. Historically, these candidates have waited substantially longer than their unsensitized or lowly sensitized counterparts and died at the same rate that they received transplants. To understand the relative roles of antibody profile versus allocation priority among highly sensitized candidates, we conducted a simulation using 2010 wait-list data, in which sensitized kidney-alone candidates received highest priority for compatible kidneys. CPRA and compatibility were based on unacceptable antigens in UNET. Simulation priority for kidney allocation was first to candidates with CPRA=100, then 99, 98, etc.

Of 13,591 deceased donor kidneys, 13,118 would have been offered to highly sensitized candidates (and presumably transplanted), versus the 1517 actually transplanted in 2010 under the current allocation system. As shown, >80% of candidates with CPRA 90%-99% had compatible donors. Not surprisingly, fewer candidates (47.6%) with CPRA 100% had compatible donors, and fewer offers came to candidates with CPRA 80%-89% since their compatible donors had already been allocated to candidates with higher PRA. These data demonstrate that, in one year, most highly sensitized candidates have (virtually) compatible donors and can potentially receive transplants, pointing to the allocation system, not the antibody profile, as the major barrier to transplant for these candidates.

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