Impact of ABO blood group incompatibility on the outcomes of allogeneic hematopoietic stem cell transplantation

Background and aim: ABO and Rh compatibility are not required between the donor and recipient for allogeneic hematopoietic stem cell transplantation (alloHSCT). Although ABO incompatibility is not considered a contraindication in alloHSCT, its clinical outcomes are still doubtful. In this study, we analyzed the neutrophil and platelet recovery, graft versus host disease (GVHD), relapse rate, mortality rate, non-relapse mortality and survival in patients who underwent alloHSCT. Materials and methods: Two hundred and sixty four patients with hematological malignant diseases, aplastic anemia and inborn errors of metabolism or the immune system that received an alloHSCT in our HSC transplant center between the years of 2001 and 2018 were evaluated. Results: Indications for alloHSCT included both hematological malignancies (n = 233), aplastic anemia (n = 25) and benign conditions (n = 6). Of these donor recipient pairs, there were 189 (71.6%) matches, 36 (13.6%) major, 29 (11%) minor and 10 (3.8%) bidirectional ABO mismatches. The seventy-four (41.6%) of the ABO match and 27 (38.6%) of the ABO mismatch patients developed GvHD. The 5-year overall survival (OS) was ABO match group and ABO mismatch group were 65% and 73%, respectively (p = 0.36). The 5-year diasease free survival (DFS) for ABO match group and ABO mismatch group were 60% and 69%, respectively (p = 0.17). Conclusion: In conclusion, this study showed that ABO mismatch did not seem to have a significant effect on major outcomes after alloHSCT, such as developing GVHD, relapse rate, mortality rate, DFS and OS. ABO incompatibility did not lead to delayed platelet and neutrophil engraftment after alloHSCT.