Red Cell Alloimmunization Rate in Patients with Sickle Cell Disease

Background: Sickle cell disease(SCD) is a single gene disorder resulting in dysfunctional hemoglobin tetramers that polymerize causing vaso-occlusion (VOC), hemolysis, endothelial damage and inflammation leading to pain and end-organ damage. Red blood cell (RBC) transfusions are vital despite recent advances in treatment. RBC alloimunization complicates treatment with rates of up to 47% limiting availability of compatible RBC units. The etiology of alloimmunization is multifactorial; including donor recipient racial differences, transfusion volume, non-leukoreduced RBCs, infection or VOC during transfusion, age, and pregnancy. Two studies have shown decreased alloimmunization rates in leukemia patients post implementation of universal leukoreduction and ABO identical (ABO-ID) blood product transfusions. The aim of this study is to analyze the impact of ABO-ID policy on alloimmunization rates in the SCD population.

Methods: A retrospective chart review was performed during June 1, 2004 to Dec 31, 2023. 437 patients with SCD were identified. Data was gathered on transfusion history, alloimmunization status, and antibodies identified.

Results: 257 patients were transfused and of that 211 were transfused prior to ABO-ID policy implementation in April 2005 (pre ABO-ID) and 49 after (post ABO-ID). In regard to SCD genotype, 67% were SS, 22% SC, and 11% SBthal. The alloimmunization rate for pre ABO-ID is 30% and post ABO-ID is 4% (p=0.0006). Among the pre ABO-ID group, 182 received ABO-ID transfusions with an alloimmunization rate of 27% compared to a rate of 48% for those transfused with ABO non-identical (ABO non-ID). The post ABO-ID group received significantly less transfusions and were younger compared to those transfused with ABO-ID RBC from the pre ABO-ID group (p<0.05 and p<0.05 respectively).

Conclusion: The alloimmunization rate in patients transfused prior to the ABO-ID policy was higher compared to those transfused after. These results suggest that avoiding the infusion of ABO non-ID antibody, even in small amounts, as with group O RBC transfused to non-O patients, may reduce the rate of alloimmunization in patients with SCD. The increased alloimmunization rate in patients transfused with ABO-ID RBCs prior to ABO-ID policy can be explained by record review limitations due to patients seeking care at outside facilities where transfusion history access was not possible, older age, and higher number of RBC units transfused. This study highlights the need for a better understanding of the risks and pathophysiology of alloimmunization in patients with SCD. Prospective multicenter studies are needed to further evaluate the long term effect of ABO-ID transfusions in this patient population.

Blumberg:Lindis Bloodcare: Consultancy; Bristol Meyers Squibb: Honoraria.