Abstract
Background - Variability in blood donors, components, and recipients are known to affect transfusion outcomes, yet the combined effects of these factors remains unclear.
Materials and methods - The Red Blood Cell - Improving Transfusions for Chronically Transfused Recipients (RBC-IMPACT) study was a multi-center longitudinal study conducted in the United States (US) and Brazil over two years to investigate RBC survival after transfusion (Aim 1) and acute increase in iron post transfusion (Aim 2) (see https://clinicaltrials.gov/study/NCT05255445). The US RBC-IMPACT study included patients with thalassemia and sickle cell disease (SCD) and, in Aim 2 only, children with hematology-oncology diseases with a hypoproliferative bone marrow. In Brazil, the study was conducted within an established SCD cohort. Blood samples were collected immediately before and after RBC transfusion to measure hemoglobin (Hb), hemoglobin A (HbA) in SCD, and markers of iron and hemolysis. Samples were collected two hours post transfusion in a subset of participants receiving primarily single unit transfusions for Aim 2. Transfusate samples were collected from transfused units. Single nucleotide polymorphism array typing of donors and recipients to measure genetic variants including those associated with increased in vitro hemolysis of stored RBCs was conducted. Comprehensive information regarding donors, components and some recipient data were linked to key clinical data extracted from recipients’ medical records to assess factors associated with RBC transfusion effectiveness.
Results - The outcomes for Aim 1 were RBC survival between successive transfusions, calculated as ΔHbA per day for SCD and by ΔHb per day for thalassemia, and Δbilirubin for both patient groups. The primary outcome for Aim 2 was change in serum iron from before to 2 hours after transfusion.
Discussion - This study will be the most detailed and granular evaluation of the predictive variables that may optimize RBC effectiveness and safety in these chronically transfused patient populations.
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