P010 Complex constellation of HLA antibodies contributes to decreasing trend of kidney transplant rate in candidates with 100% CPRA

Aim The key component of the new kidney allocation system is increased priority for sensitized candidates. While transplants (tx) have increased 6 fold for recipients with a CPRA of ⩾99%, the trend in tx for these patients began to decrease over the 1 st year. To determine if HLA antibody composition contributes to the decreasing tx rate, we compared the distribution of Cross-REactive Groups (CREG) in our waitlist candidates with different CPRA ranges. Method Kidney waitlist candidates ( n  = 5281) were tested for HLA antibodies using One Lambda single antigen beads on DTT-treated sera. CPRA values were determined based on unacceptable antigens (UA), and were clustered into 100%, 99%, 98%, 80–97% and 20–79% CPRA groups. Results The number of UA differs significantly between CPRA groups (Table). The 100%-CPRA group display 18–107 UA (98% of this group display >25 UA and 72% display ⩾50 UA). The 99%-CPRA group display 13–61 UA (78% display ⩾25 UA) while the 98%-CPRA group display 8–60 UA (66% display ⩾25 UA). The incidence of CREG HLA antibodies differs significantly among CPRA groups. Most candidates with 100% CPRA display 2–3 fold increase in the number of CREGs compared to candidates with 99% or 98% CPRA. More than 3 CREGs were observed in 63.8% of the 100%-CPRA group, but only in 21.3% of the 99%-CPRA group, in 2% of the 98%-CPRA group and in 1.4% of the 80–97%-CPRA group. Candidates with CPRA Conclusions These results suggest that the majority of the candidates in the100%-CPRA group 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.