ABO-incompatible HSCT in Practice: Graft Processing Decisions, Titer Thresholds, and Transfusion Management

Proposed Session Description: ABO incompatibility occurs in approximately 30-50 % allogeneic hematopoietic stem cell transplants (HSCT) and represents one of the most common immunohematologic challenges encountered by transplant programs, transfusion services, and cellular therapy laboratories. Although ABO mismatch is not a contraindication to transplantation, it introduces important risks including acute hemolysis, passenger lymphocyte syndrome, and delayed erythroid engraftment. Management of ABO incompatible HSCT requires coordinated decision making across the transplant team, transfusion medicine service, and cell therapy laboratory. However, key aspects of practice remain highly variable across institutions. Differences commonly exist in donor and recipient isohemagglutinin testing, thresholds used to guide graft manipulation, and approaches to managing minor and major ABO incompatible peripheral blood stem cell and bone marrow grafts.
Recent changes in cellular therapy laboratory practice have further highlighted these challenges. Many programs are transitioning from legacy manual graft manipulation methods to automated cell processing platforms, enabling more standardized approaches to plasma and red cell depletions. Increasing transplant volumes, variable staff experience with manual graft manipulation, and supply fluctuations affecting reagents commonly used for manual red cell depletion may also influence institutional considerations when selecting processing strategies. Regulatory frameworks such as AABB and FACT standards further emphasize validated procedures, defined product specifications, and documented decision criteria for graft manipulation.
This session will review current evidence and institutional practices for managing ABO incompatible HSCT, with a focus on practical decision making in the cell therapy laboratory and transfusion service. Speakers will discuss graft manipulation strategies for peripheral blood stem cell and bone marrow products, operational considerations associated with automated processing platforms, and transfusion support following transplantation. Case based discussion will highlight common clinical scenarios encountered in practice.