Impact of the 2014 kidney allocation system changes on trends in A2/A2B into B kidney transplantation and organ procurement organization reporting of donor subtyping

Abstract

The current kidney allocation system (KAS) preferentially allocates kidneys from blood type A2 or A2B (A/A2B) donors to blood type B candidates. We used national data to evaluate center-level performance of A2/A2B to B transplants, and organ procurement organization (OPO) reporting of type A or AB donor subtyping, in 5-year time periods prior to (2009)(2010)(2011)(2012)(2013)(2014) and following (2015-2019) KAS implementation. The number of centers performing A2/A2B to B transplants increased from 17 pre-KAS to 76 post-KAS, though this still represents only a minority of centers (7.3% pre-KAS and 32.6% post-KAS). For high-performing centers, the median net increase in A2/A2B to B transplants was 19 cases (range -2-72) per center in the 5 years post-KAS. The median net increase in total B recipient transplants was 21 cases (range -17-119) per center.Despite requirements for performance of subtyping, in 2019 subtyping was reported on only 56.4% of A/AB donors. This translates into potential missed opportunities for B recipients, and even post-KAS up to 2322 A2/A2B donor kidneys may have been allocated for transplantation as A/AB. Further progress must be made both at center and OPO levels to broaden implementation of A2/A2B to B transplants for the benefit of underserved recipients.

Increasing Access to Kidney Transplantation for Black and Asian Patients Through Modification of the Current A2 to B Allocation Policy

“…13 The KAS, implemented on December 4, 2014, was designed to decrease disparities in transplantation by implementing new changes to the allocation algorithm, including allocating blood subgroup A2/A2B deceaseddonor kidneys to candidates with blood type B. 14 This change was made on the basis of improved long-term survival outcomes when the OPTN implemented variance of practice policies in 2002 to allow DDKT with A2 donors to B recipients. This prospective variance study showed an increase in access to kidney transplantation for minority candidates by as much as 36%, depending on donor service area in the study.…”

“…However, 157 transplant centers did not perform a single A2/A2B to B transplant at this time. 14 More importantly, they found that from 2015 to 2019, only 56.4% of A/AB donors were subtyped after implementation of the KAS. 14 The authors also found that 1161 A/AB donors went unrecognized as possible A2/A2B donors because of lack of subtyping.…”

“… 14 More importantly, they found that from 2015 to 2019, only 56.4% of A/AB donors were subtyped after implementation of the KAS. 14 The authors also found that 1161 A/AB donors went unrecognized as possible A2/A2B donors because of lack of subtyping. With the assumption that each candidate donated both kidneys, 2322 possible kidneys went unrecognized as potentially compatible with B group patients, undermining the allocation policies of the KAS.…”

“…Even half of this number would have had a meaningful effect, leading to a potential 24% increase in the rate of B-recipient DDKT in the post-KAS period. 14 The reason behind the lack of subtyping is multifactorial. Frequently cited issues, however, include donor transfusions or discordant testing.…”

“…Having recorded explanations may be one avenue for possible modifications and improvements in the KAS policy to maximize the potential benefits of ABO-i transplantation. 14 …”