University of North Carolina, Chapel Hill. NC Haw River, North Carolina, United States
Background/Case Studies: The therapeutic effectiveness of chronic transfusion therapy (CTT) depends on the survival of transfused red blood cells (RBCs). However, the factors influencing donor-HbA clearance (ΔHbA)—including recipient characteristics, donor characteristics, and RBC component features—remains poorly defined. One prior study in pediatric patients with sickle cell anemia (SCA) suggested that the presence of RBC antibodies increased ΔHbA. However, this observation has not been confirmed. This study aims to elucidate the predictors of ΔHbA among adult patients with SCA undergoing chronic red cell exchange (RCE), with a particular focus on the presence of red cell antibodies.
Study
Design/Methods: We conducted a two-year (Jan 2021–Jan 2023) retrospective observational study of Sixty-five adults with SCA who underwent ≥2 RCEs and had complete Hb electrophoresis data. Procedures with missing data or interim RBC transfusions outside scheduled RCEs were excluded. Patients were stratified by baseline RBC antibody status, defined as the presence of any clinically significant allo- or autoantibody at the start of the data collection period. Demographic, clinical, and transfusion data were collected. ΔHbA was calculated by determining the change between posttransfusion HbA (g/dL) and the pretransfusion HbA (g/dL) of the next RCE, divided by days between exchanges and normalized over 28 days. Univariable linear regressions and mixed-effects modeling assessed associations between ΔHbA and variables including age, sex, genotype, baseline antibody status, RBC unit features, and the clinically defined exchange parameters. A boxplot was used to visualize intrapatient variability in ΔHbA.
Results/Findings: A total of sixty-five patients and 1,294 RCE procedures were analyzed. Mean age was 30 years; 48% were male; and 86% were HbSS. The boxplot (see Figure 1) highlights the wide intrapatient variability in ΔHbA. In univariable analysis, younger age (parameter estimate [PE] -0.01 per year; 95% CI: -0.03 to 0.00; p = 0.025), and male sex (PE 0.32; 95% CI: 0.00 to 0.65; p = 0.048) were significantly associated with higher ΔHbA. Patient baseline antibody status, RBC unit storage age, the use of HbC trait donor units, splenomegaly, and the formation of new alloantibodies during the study period were not significantly associated with ΔHbA.
Conclusions: Recipient factors such as age and sex were associated with donor HbA clearance following RCE. The baseline presence of RBC antibodies and other transfusion-related parameters were not linked to ΔHbA. These findings support recipient-based stratification over product modification to optimize HbA retention. Prospective studies are needed to confirm these results and guide personalized transfusion strategies.
