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Unintended Consequences of the New National Kidney Allocation Policy in the United States
A R Tambur1, K M K Haarberg1, J J Friedewald1
1Comprehensive Transplant Center, Feinberg School of Medicine, Northwestern University, Chicago, IL.
Abstract:
The new national Kidney Allocation System of the Organ Procurement and Transplantation Network (OPTN), effective as of December 4, 2014, was designed to improve the chances of transplanting the most highly sensitized patients on the waitlist, those with calculated panel reactive antibody values of 98%, 99% and 100%. Recently, it was suggested that these highly sensitized patients will experience inequitable access, given the reported high prevalence of antibodies to HLA-DP, and the fact that only about 1/3 of deceased donors are typed for HLA-DP antigens. Here we report that 320/2948 flow cytometric crossmatches performed for the Northwestern transplant program over the past 28 months were positive solely due to HLA-DP donor-specific antibodies (11%; 16.5% of patients with HLA antibodies-sensitized patients). We further show that 58/207 (12%) HLA-DR serologically matched donor-recipient pairs had a positive B cell flow crossmatch due to donor-specific HLA class II antibodies, and 2/34 (6%) serologic zero-HLA-A-B-DR mismatch had a positive flow crossmatch due to HLA-DSA. We therefore provide information regarding the necessity and importance of complete donor HLA typing including both chains of the HLA-DP antigen (encoded by HLA-DPA1 and HLA-DPB1) at the time of organ offer.
Insights
The new kidney allocation system may disadvantage highly sensitized patients due to HLA-DP antibodies. Complete donor HLA typing, including HLA-DP, is crucial for equitable kidney transplants.
Area of Science:
- Immunogenetics
- Transplantation immunology
- Nephrology
Background:
- The Organ Procurement and Transplantation Network (OPTN) implemented a new Kidney Allocation System in 2014 to prioritize highly sensitized patients.
- Concerns exist regarding equitable access for these patients due to HLA-DP antibodies and incomplete donor typing.
Purpose of the Study:
- To investigate the impact of HLA-DP donor-specific antibodies on crossmatch outcomes in kidney transplantation.
- To assess the necessity of comprehensive donor HLA typing, including HLA-DP, for improving transplant equity.
Main Methods:
- Analysis of flow cytometric crossmatches from the Northwestern transplant program over 28 months.
- Evaluation of positive crossmatches attributed to HLA-DP donor-specific antibodies (DSAs).
- Assessment of HLA-DR matched and zero-HLA-A-B-DR mismatched pairs with positive crossmatches due to HLA class II DSAs.
Main Results:
- 11% of crossmatches were positive solely due to HLA-DP DSAs.
- 16.5% of patients with HLA antibodies experienced HLA-DP DSA-positive crossmatches.
- 12% of HLA-DR matched pairs and 6% of zero-HLA-A-B-DR mismatch pairs had positive crossmatches due to HLA class II DSAs.
Conclusions:
- HLA-DP DSAs frequently cause positive crossmatches, potentially hindering transplants for highly sensitized patients.
- Complete donor HLA typing, encompassing both HLA-DPA1 and HLA-DPB1, is essential at the time of organ offer.
- Comprehensive typing ensures equitable organ allocation and improves outcomes for patients awaiting kidney transplants.
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