The key component of new KAS is offering an increased priority for sensitized candidates. While transplants (tx) have increased six-fold for recipients with a CPRA of >99%, the trend in tx for these patients has begun to decrease over the first six months. To determine if HLA antibody composition contributes to such decreasing tx rate, we compared HLA antibody constellations (called Cross-REactive Groups, CREG) in our waitlist candidates with different CPRA ranges (Table 1).

Over 86% of the highly sensitized candidates with a CPRA >80% are either re-tx candidates (27.6%) or female candidates waiting for first-tx (58.8%), while 47.9% of the candidates with a CPRA score 20-79% are male waiting for the first-tx (only 3.8% are re-tx candidates). Strikingly, 47% of the 100%-ners are re-tx candidates while only 20% of the 99%-ners are re-tx candidates.

The number of unacceptable antigens (UA) differs significantly between CPRA groups. The 98%-CPRA group display 8-60 UA (66% display >25 UA) while the 99%-CPRA group display 13-61 UA (78% display >25 UA). Conversely, the 100%-CPRA group display 18-107 UA and 98% of this group display >25 UA (72% display >50 UA).

The incidence of CREG HLA antibodies (such as 1C, 2C, 4C, 5C, 6C, 7C, 8C, 10C, 12C, C1, C2, DR1C, DR51C, DR52C and DR53C) differs significantly among CPRA groups. Candidates with 100%-CPRA display 2-3 fold increase of most of these CREGs compared to candidates with 98% or 99% CPRA. Moreover, 52% of 100%-CPRA candidates display >3 CREGs while only 13.3% of candidates with 99% and 22.2% of candidates with 98% CPRA display 3 CREG, and none of the <100 CPRA candidates display >3 CREG.

Over 80% of 100%-CPRA candidates are homozygotes at multiple HLA loci, and display antibodies to all antigens of one or more HLA loci except to the self-antigens. Moreover, the probability of finding a zero HLA-A/B/DR antigen mismatched kidney is zero for 43.6% of 100%-CPRA candidates. These results suggest that the majority of 100%-CPRA candidates are very broadly sensitized and are hard to find a compatible kidney, and thus need an alternative approach such as desensitization and living-donor kidney exchange. These data support the importance of HLA matching at least at the level of CREG antigens.

CITATION INFORMATION: Rajalingam R, Hyon Gae D, Kopchaliiska D, Buenaventura O, Cunniffe K, Da Gente G, Roberts J. Complex Constellation of HLA Antibodies Contributes to Decreasing Trend of Transplant Rate in Candidates with 100% CPRA. Am J Transplant. 2016;16 (suppl 3).

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