Discrepant subtyping of blood type A2 living kidney donors: Missed opportunities in kidney transplantation

A2/A2B to B deceased donor kidney transplantation in the Kidney Allocation System 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 data from the Scientific Registry of Transplant Recipients from December 2014 until June 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"). The rates of DDKT at 1-, 3-, and 5-years were 32.1%, 61.4%, and 72.1% among A2-eligible candidates and 14.1%, 29.9%, and 44.1% among A2-ineligible candidates, with the former experiencing a 133% higher rate of DDKT (Cox weighted hazard ratio (wHR) = 2.192.332.47; P < .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 = .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 > .9) or all-cause graft loss (wHR 0.820.961.12, P = .6). Following its broader adoption since the implementation of the kidney allocation system, 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.

Impact of sensitization and ABO blood types on the opportunity of deceased-donor kidney transplantation with prolonged waiting time

The waiting time to deceased-donor kidney transplantation (DDKT) is long in Asian countries. We investigated the impact of sensitization and ABO blood type (ABO) on DDKT opportunity using two Korean cohorts: a hospital cohort from two centers and a national database. The impact of panel reactive antibody (PRA) based on the maximal PRA% and ABO on DDKT accessibility was analyzed using a competing risks regression model. In the hospital cohort (n = 4722), 88.2%, 8.7%, and 3.1% of patients belonged to < 80%, 80-99%, and ≥ 99% PRA groups, respectively, and 61.1%, 11.6%, and 27.3% belonged to A or B, AB, and O blood types, respectively. When PRA and ABO were combined, PRA < 80%/A or B and 80 ≤ PRA < 99%/AB had fewer DDKT opportunities (median, 12 years; subdistribution hazard ratio [sHR], 0.71) compared with PRA < 80%/AB (median, 11 years). Also, PRA < 80%/O, 80 ≤ PRA < 99%/A or B, and PRA ≥ 99%/AB had a much lower DDKT opportunity (median, 13 years; sHR, 0.49). Furthermore, 80 ≤ PRA < 99%/O and PRA ≥ 99%/non-AB had the lowest DDKT opportunity (sHR, 0.28). We found similar results in the national cohort (n = 18,974). In conclusion, an integrated priority system for PRA and ABO is needed to reduce the inequity in DDKT opportunities, particularly in areas with prolonged waiting times.