Incidence of acute haemolytic transfusion reaction among ABO‐incompatible recipients transfused with A3 blood: A case series

Abstract

AbstractBackground and ObjectivesABO antigens are among the most immunogenic, but the haemolytic risks of ABO incompatibilities involving a donor with a weak ABO phenotype are little documented.Materials and MethodsThis retrospective case series assessed the incidence of acute haemolytic transfusion reaction (AHTR) among ABO‐incompatible recipients of A3 blood in Québec (Canada). Transfusion safety officers reported laboratory AHTR indicators measured ≤24 h pre‐ and post‐transfusion. Because the AHTR case definition of Québec's Hemovigilance System (QHS) leaves significant room for clinical judgement, a two‐step approach was used to assess potential cases: Step 1 consisted in a highly sensitive—but unspecific—initial screen that identified all candidate cases per QHS case definition, and Step 2 consisted in a detailed review of candidate cases by two haematologists.ResultsNine donors initially typed as Group B (N = 1) or O (N = 8) were subsequently found to display an A3B or A3O phenotype. Eighty‐one recipients received ABO‐incompatible blood, including 53 (65.4%) with interpretable data. Of these, 29 (54.7%) were classified as candidate cases after Step 1. Following Step 2, no conclusive evidence of AHTR was found: Abnormal pre‐ versus post‐transfusion changes appeared modest, within normal range, insufficient to ascertain AHTR, or were consistent with a pre‐existing condition unrelated to AHTR. Two candidate cases had a QHS‐reported transfusion reaction; both were unrelated to AHTR.ConclusionIn this case series, no conclusive evidence of serious AHTR was found among ABO‐incompatible recipients who were inadvertently transfused with A3 blood.