RBCs from patients with SCD present higher surface GPA expression with reduced Siglec-9-Fc binding. The median fluorescence intensity (MFI) of surface GPA was measured on healthy RBCs (blue) and on RBCs of patients with SCD pretransfusion (red) (n = 9) (A). The MFI for Siglec-9-Fc binding (B) was measured in RBC from healthy RBCs (blue), RBCs of patients with SCD pretransfusion (n = 4) (red), and from patients with untransfused SCD with >90% HbS (n = 2) (marked with squares); comparison performed using unpaired t tests. Error bars represent standard deviation. ∗ P < .05.