Purpose: The new kidney allocation system (KAS) was implemented to help identify compatible donors for the most highly sensitized patients. Our experience, as well as others, is that it is the same patient population that exhibit antibodies (Abs) that currently cannot be imported into UNET. These include antibodies to HLA-DP, HLA-DQ (specifically as DQα/b combinations) and allele level Abs to antigens in other HLA-loci. Herein we evaluated the impact of assigning HLA antigens and Abs at higher resolution on kidney organ offers for patients qualifying for the new KAS.

Methods: UNOS database was queried for all regional and national kidney-alone offers to our center between 12/4/2014 – 12/03/2015 (N = 285). Histocompatibility consultation provided in real-time included data obtained from UNET as well as additional donor HLA antigen higher resolution information obtained via laboratory specific attachments or calling the donor HLA typing laboratory. All offers deemed unacceptable due to a patient having HLA Abs was included in this study with UNET offer responses: 810, 811, 813, 815 (N = 82).

Results: The calculated panel reactive antibody values for all of the recipients were ≥98%. 6/285 (~1%) of the kidneys were placed at our center. 82/285 (29%) of import offers were declined based on virtual XM due to HLA Abs being clinically unacceptable. None of those organs were brought in for a physical XM. Of these, 20% were HLA class I (16/82), 56% class II (46/82) and 24% class I + II (20/82). HLA Abs most frequently determined to be unacceptable were HLA-DQ [29% (24/82)] and HLA-DP [37% (30/82)], excluding 3 offers with no donor DP typing available and the recipients having strong DP Abs. Taken together, ~66% (54/82) of the import offers listed as unacceptable were DQ + DP.

Conclusion: The new KAS had significantly increased the number of potential kidney offers to highly sensitized patients. However, ˃[frac14] of these offers had unacceptable donor specific Abs. Importantly, in the vast majority of these cases, information regarding high-resolution HLA Abs and antigens were available at the time of offer (recipient and donor HLA laboratories) albeit not in UNET. Our results, using real time data, provide strong support for the value of high resolution HLA information especially for the highly sensitized patients. UNOS is about to roll out some of the required changes. We strongly urge the community to continue evaluating needs for information regarding DQα/b combinations and allele level antibodies.

CITATION INFORMATION: Cusick M, Friedewald J, Haarberg K, Leventhal J, Tambur A. Improving Kidney Allocation System with Higher Resolution. Am J Transplant. 2016;16 (suppl 3).

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