A Cautionary Tale: ABO Genotyping in Kidney Transplantation of ABO A2 Kidneys Into B or O Recipients

Abstract

The US 2014 kidney allocation system (KAS) allows ABO A₂ donor kidneys to be transplanted into ABO B candidates, thereby broadening the donor pool for a traditionally disadvantaged population. Safely transplanting these patients relies heavily on two components: (1) recipient ABO antibody titres and (2) ABO A subtyping of the donor. While lectin-based serological methods remain the gold standard for ABO typing, recent data show ABO molecular genotyping is a more reliable approach to accurately assign the A₂ subtype. ABO titres were performed using Ortho Diagnostics gel cards using haemagglutination by both antiglobulin-enhanced and dithiothreitol methods. ABO genotyping was performed using innotrain diagnostiks Real-Time PCR. Here, we present two cases where ABO lectin testing incorrectly identified the donors as ABO A₂ and A₂B instead of A₁ and A₁B. Consequently, the transplants proceeded but had deleterious outcomes. These two cases support the concept that ABO genotyping by molecular methodology should be mandatory to confirm the A₂ donor subtype when transplanting kidneys from deceased donors into ABO B candidates on the waitlist and for virtual crossmatching (VXM) donors being considered for transplantation into ABO B and O recipients.