A2/A2B to B Deceased Donor Kidney Transplantation in the KAS Era

Kidney transplantation from blood type A2/A2B donors to type B recipients (A2→B) has increased dramatically under the current Kidney Allocation System (KAS). Among living donor transplant recipients, A2-incompatible transplants are associated with an increased risk of all-cause and death-censored graft failure. In light of this, we used SRTR data from 12/2014-6/2022 to evaluate the association between A2→B listing and time to deceased donor kidney transplantation (DDKT) and post-DDKT outcomes for A2→B recipients. Among 53,409 type B waitlist registrants, only 12.6% were listed as eligible to accept A2→B offers ("A2-eligible"). 1-/3-/5-year DDKT rates were 32.1%/61.4%/72.1% among A2-eligible candidates and 14.1%/29.9%/44.1% among A2-ineligible candidates, with the former experiencing a 133% higher rate of DDKT (Cox weighted HR = 2.192.332.47; p<0.001). The 7-year adjusted mortality was comparable between A2→B and B-ABOc (type B/O donors to B recipients) recipients (wHR 0.780.941.13, p=0.5). Moreover, there was no difference between A2→B vs. B-ABOc DDKT recipients with regards to death-censored graft failure (wHR 0.771.001.29, p>0.9) or all-cause graft loss (wHR 0.820.961.12, p=0.6). Following its broader adoption since the implementation of KAS, A2→B DDKT appears to be a safe and effective transplant modality for eligible candidates. As such, A2→B listing for eligible type B candidates should be expanded.