Among pediatric patients with sickle cell anemia (SCA), chronic blood transfusion (BT) may play an essential role in regulating endothelial cell quiescence, and consequently thrombin generation, according to research presented at the ISTH 2022 Congress.

SCA, which is characterized by chronic hemolysis, hypercoagulability, and thrombosis, may lead to symptomatic stroke in up to 10% of pediatric patients, which may lead to life-long physical disabilities. Although novel therapeutic interventions have led to improved outcomes among some patients, the standards of care remain BT and hydroxycarbamide.

Despite their regular use in this patient population, it was previously unclear how, biologically speaking, BT and hydroxycarbamide reduce thrombotic risk. For this study, researchers evaluated whether BT and hydroxycarbamide reduce SCA-related endothelial cell activation, thereby affecting patient thrombotic risk.

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Overall, 180 patients were recruited for this study (84 in the BT arm and 96 in the hydroxycarbamide arm). The researchers explored patient Weibel Palade body WPB markers, including VWF:Ag, VWF multimers, VWF propeptide, factor VIII:C, angiopoeitin-2, osteoprotegerin, plasma ADAMTS-13, and thrombin generation.

Among 80 patients in each arm included in the baseline analysis, the median age was 12 and 100% of patients were African. Laboratory parameters, including hemoglobin levels, platelet counts, and neutrophil counts were significantly different between the BT and hydroxycarbamide groups.

Among patients treated with BT, plasma VWF:Ag, VWF:CB and VWF propeptide were all significantly reduced; plasma levels of Weibel Palade body biomarkers, including angiopoeitin-2 and osteoprotegerin, were also lower in the BT arm. No differences were, however, noted in ADAMTS13 activity, though the VWF/ADAMTS13 ratio was increased in the BT group.

The authors also noted that coagulation activation markers — factor VIII:C levels, endogenous thrombin potential, and peak thrombin — were lower in the BT arm.

“This is the first large study to directly address the effects of BT on SCA endotheliopathy and coagulopathy,” the authors wrote. “Importantly, our novel data demonstrate that BT plays a critical role in maintaining normal [endothelial cell] quiescence and thus thrombin generation in SCA children.”


Fogarty H, Ward S, Karampini E. Blood transfusion maintains endothelial cell quiescence – implications in the prevention of stroke in paediatric sickle cell anaemia. Poster presented at: ISTH 2022 Congress; July 9-12, 2022. Abstract PB0351.