Isoagglutinin dynamics and transfusion dependency after ABO-incompatible haematopoietic stem cell transplants.

BACKGROUND

ABO incompatibility is common in allogeneic haematopoietic stem cell transplantation (HSCT) and may delay erythroid recovery and prolong transfusion support. Data correlating post-transplant isoagglutinin kinetics with transfusion dependency is limited.

METHODS

We retrospectively analysed ABO-incompatible allogeneic HSCTs performed between June 2008 and December 2023. Patients were classified as major, minor or bidirectional incompatibility. Serial Immunoglobulin M (IgM) and Immunoglobulin G (IgG) anti-A and anti-B isoagglutinin titres were monitored post-transplant. Time to isoagglutinin disappearance, donor red blood cell (RBC) appearance and associations with packed red blood cell (PRBC) and single donor platelet (SDP) transfusion requirements were evaluated.

RESULTS

Among 459 allogeneic HSCTs, 183 (39.9%) were ABO-incompatible. Median isoagglutinin disappearance was 28 days in major and 38.5 days in bidirectional incompatibility, with delayed donor RBC appearance in the latter. Anti-A isoagglutinins persisted longer than anti-B. Persistent isoagglutinins correlated with increased early PRBC and SDP transfusion requirements.

CONCLUSIONS

Isoagglutinin kinetics vary by ABO incompatibility type and are associated with early transfusion dependency after HSCT.