Renato M. Vega

Red blood cell transfusions and the risk of allosensitization in patients awaiting primary kidney transplantation.

Background Most studies of HLA sensitization after red blood cell transfusion in transplant candidates were done before widespread use of leukoreduced blood and based on relatively insensitive, nonspecific antibody assays. We evaluated the effect of transfusion on the breadth and magnitude of HLA antibody formation using current, sensitive, HLA-specific immunoassays. Methods Serial HLA antibody data were merged with transfusion data from the US Renal Data System for 1324 patients on the kidney transplant waitlist (2004–2010). Two study groups were identified: a matched cohort consisting of 89 patients who received transfusion and 251 patients who did not receive transfusion and a crossover cohort consisting of 69 patients. Changes in antibody levels and calculated panel-reactive antibody (CPRA) were compared using &khgr;2 and Sign tests, respectively. Logistic regression was used to estimate the relative risk of antibody responses. Results Among the matched cohort, 20% of those who received transfusion compared to 3% of those who did not receive transfusion exhibited an antibody response (P=0.001), whereas in the crossover cohort, 19% exhibited a response in those who received transfusion compared to 1% of those who did not receive transfusion (P=0.0001). Moreover, 26.3% of those who received transfusion had increased CPRA compared to 5.8% of those who did not receive transfusion . These effects were greater in women and blacks compared to men and whites, respectively. Importantly, patients who received transfusion were at an increased risk of a potentially crossmatch positive response (odds ratio=9.6, 95% confidence interval=3.0–30.7). Conclusions Sensitization from transfusion can occur in up to 20% of transplant candidates, resulting in higher antibody levels and CPRA values that adversely impact access to transplantation. These results support transfusion avoidance whenever possible.

Casting a smaller net into a bigger donor pool: A single center’s experience with the new kidney allocation system

The new kidney allocation system (KAS) provides additional allocation points for candidates with broad HLA sensitization in an effort to increase transplant rates for this underserved population. Following the implementation of KAS, our center lowered the HLA antibody threshold for listing unacceptable antigens from a cytotoxicity crossmatch level to a flow cytometric crossmatch level increasing Calculated Panel Reactive Antibody (CPRA) values and allocation points, yet restricting acceptable donor HLA phenotypes. As a result, many sensitized candidates were transitioned from 50% to 98% CPRA categories into the 99% CPRA regional share and 100% CPRA national share categories. Exposure to these larger donor pools significantly increased transplantation with compatible donors for 100% CPRA candidates, but regional sharing was not sufficient to increase transplantation rates for our 99% CPRA candidates. Competition within the 100% CPRA cohort identified inequities for 99.99-100.0% CPRA candidates and highlighted the continued need for desensitization therapies to reduce immunological barriers and provide transplant opportunities for the most highly sensitized candidates.