Transfusions in autoimmune hemolytic anemias: Frequency and clinical significance of alloimmunization.

Abstract

Autoimmune hemolytic anemia (AIHA) may be associated with transfusion reactions and risk of alloimmunization. To evaluate the transfusion policy and rate of alloimmunization and its clinical significance in AIHA. Data from 305 AIHA patients followed at a reference hematologic Center in Milan, Italy from 1997 to 2022 were retrospectively/prospectively collected (NCT05931718). Overall, 33% patients required transfusions with a response rate of 83% and eight transfusion reactions (7%), none hemolytic. Alloantibodies were detected in 19% of patients, being associated with higher transfusion burden (p=0.01), lower Hb increase post-transfusion (p=0.05), and transfusion reactions (p=0.04). Along decades, the rate of RBC transfusions decreased from 53% to 20% and that of alloimmunization dropped from 30% to 6% likely due to the adoption of prestorage leukoreduction, the use of more restrictive Hb thresholds, and the implementation of molecular typing. Severe symptomatic AIHA may be safely transfused provided appropriate matching of patients and donors.