Should the Current Zero HLA ABDR-Mismatch Priority in Kidney Allocation System Continue?: A Critical Appraisal

Zero HLA ABDR mismatch priority in the Kidney Allocation System is highly biased against minority candidates. Zero HLA ABDR mismatch priority shunts 2.5% of O donors to nonidentical blood types disadvantaging O recipients. Zero HLA ABDR-mismatch priority recipients have substantially shorter dialysis exposure before transplant than nonpriority recipients.

In the Kidney Allocation System (KAS), adult kidney candidates who are a zero HLA ABDR-mismatch with a potential donor are given priority in the match run over nonzero HLA ABDR-mismatch candidates. Furthermore, KAS allows for the shunting of kidneys to zero-mismatch candidates across compatible ABO blood types, potentially disadvantaging O candidates who have longer waiting times. This study was undertaken to determine who is receiving zero HLA ABDR-mismatch kidneys, the number of donors shunted to nonidentical ABO recipients, the effect on dialysis exposure before transplant, and the current patient and graft outcomes.

All adult deceased donor kidney recipients since the start of KAS on December 4, 2014, were included in the study. Multiorgan transplants with a kidney, 98%-100% calculated panel reactive antibodies (CPRAs), previous living donors, pediatric, medically urgent, and safety net transplants were excluded. Patients were considered a zero-mismatch allocation if they received a zero HLA ABDR-mismatch kidney and had an allocation CPRA <98%. One hundred twenty-two thousand nine hundred and fifty-one adult deceased donor kidney transplants were in the study population. Six thousand two hundred twenty-eight, or 5.1%, were zero HLA ABDR-mismatch recipients.

The zero HLA ABDR-mismatch recipients were predominantly of the White race, female, had lower allocation CPRAs, much shorter dialysis exposure, and were more likely to be retransplant recipients. One thousand four hundred and forty-one blood type O donors were shunted to other ABO groups, or 2.46% of O donors. Cox analysis of graft and patient survival showed that zero HLA ABDR-mismatch recipients had a small graft survival advantage (0.898, 0.834 to 0.967, P = 0.004) and no patient survival advantage (0.947, 0.865 to 1.037, P = 0.239). The adjusted graft survival at 7 years was 67% (zero HLA-ABDR mismatch) versus 65% (nonzero HLA-ABDR mismatch).

The current zero HLA ABDR-mismatch priority is highly biased against racial minority recipients, shunts a sizable number of O donors to non-O recipients, only makes a small improvement to organ utility, and should be removed from the allocation priority list.