Comparison of short-term outcomes in thalassemia major ABO mismatch versus ABO compatible in allogeneic hematopoietic stem cell transplant

Objective: Allogeneic hematopoietic stem cell transplantation (HSCT) is the only curative treatment for thalassemia major. ABO incompatibility between donor and recipient is common, but its clinical significance remains uncertain. The objective of the study is to assess the impact of ABO mismatch on outcomes of HSCT in patients with thalassemia major. Methods: This ambispective single-center study included 102 patients with thalassemia major who underwent allogeneic HSCT between March 2012 and July 2023. Patients were equally divided into ABO-compatible ( n = 51) and ABO-mismatched ( n = 51) groups. Outcomes analyzed included acute graft-versus-host disease (aGVHD) and chronic graft-versus-host disease, autoimmune hemolytic anemia (AIHA), transplant-related mortality (TRM), overall survival (OS), and thalassemia-free survival (TFS). Results: ABO-mismatched transplants showed significantly higher rates of aGVHD ( p = 0.0002) and AIHA ( p = 0.004) and higher TRM ( p = 0.031). However, OS ( p = 0.293) and TFS ( p = 0.554) were comparable between the two groups. Conclusion: ABO incompatibility increases early post-transplant complications but does not significantly affect long-term survival outcomes. Human leukocyte antigen matching should remain the primary criterion in donor selection.