Beyond HLA matching: a practical framework for selecting among HLA-identical donors in hematopoietic stem cell transplantation

Abstract

Background: Donor selection in allogeneic hematopoietic stem cell transplantation (HSCT) has evolved beyond human leukocyte antigen (HLA) compatibility. Advances in transplant platforms and immunogenetics have highlighted the importance of integrating additional donor-related clinical and biological factors. Methods: This Brazilian Society of Bone Marrow Transplantation (SBTMO) consensus was developed through a critical review of the current literatureand expert discussion. It addresses the main variables influencing donor selection beyond HLA matching and provides evidence-based recommendations. Results: Donor age is the most relevant non-HLA factor and should be prioritized whenever possible. Other variables-including cytomegalovirus serostatus, ABO compatibility, donor sex and parity, germline predisposition variants, donor eligibility, and ethical considerations-should be incorporated into an individualized decision-making process. A practical algorithm summarizes the proposed recommendations. Conclusion: Donor selection should integrate HLA compatibility with clinical, biological, and ethical factors to optimize transplant outcomes. This consensus provides a practical framework to support evidence-based donor selection in contemporary allogeneic HSCT.