The impact of ABO compatibility/incompatibility between donor and recipient of allogeneic bone marrow transplant on transplant outcomes.

Background: ABO blood group mismatch between donor and recipients is not considered as a major contraindication to allogeneic hematopoietic stem cell transplantation (allo-HSCT). Nevertheless, there is still conflicting reports on the impact of ABO incompatibility on allo-HSCT outcomes, including the risk of graft-versus-host disease (GVHD), relapse of underlying disease, and patient survivals.

Methods: We conducted a retrospective cohort study in 157 patients who underwent HSCT from October 1st 2019, to September 30th 2023, to determine the effect of ABO compatibility on allo-HSCT outcomes, as evaluating for pure red cell aplasia, engraftment time/status, chronic/acute allo-GVHD, and non-relapse mortality.

Results: Overall, 50.3 % of HSCT patients were ABO incompatible and 49.7 % of allo-HSCT patients were ABO compatible. Our findings suggest that the risk of pure red cell aplasia was significantly higher in cases with the major and bidirectional ABO incompatibility (P < 0.001) with odds ratio (OR): 19.8 [95 % confidence interval (CI): 2.3-2578.9; P < 0.001), and anti-A isohemagglutinin against donor red blood cells (RBCs) in the recipient serum is an important risk factor for this complication. Our results do not show any significant relationship between ABO incompatibility/compatibility on engraftment time and graft failure. The ABO incompatibility increased RBC transfusion burden but did not affect platelet consumption, the incidence and severity of acute and chronic GVHD, patient survivals and non-relapse mortality.

Conclusions: Our findings suggest that allo-HSCT with bidirectional ABO incompatibility with anti-A isohemagglutinins are associated with the occurrence of pure erythroid aplasia. However, ABO incompatibility did not affect the risk for acute and chronic GVHD, survival of patients, and all-HSCT engraftment status.