RBC transfusions for N = 6496 pSCDs in the Paris area. (A) Number of patients receiving transfusion and number of RBCus transfused each year: 2008-2018 study period and recent 2019-2021 evolution (data added during revision). (B) Sum of all RBCus transfused per year based on the age at transfusion (curve) and comparison between year 2008 and year 2018 (histogram). (C) Mean number of RBCus per patient per year based on the age at transfusion (curve), and comparison between year 2008 and year 2018 (histogram). (D) Overlay histogram of the distribution of the number of RBCus transfused per patient, comparing the proportion of immunized and nonimmunized patients for each number of RBCus received. Data shown as percentages (of immunized or nonimmunized patients, respectively), rather than the number of patients, to facilitate visual comparison. The first bar shows that 3.8% of immunized patients and 10.5% of nonimmunized patients only received 1 unit. Data are truncated at 100 units received for clarity, but the distribution goes on with similar profile until the largest number of units received in the cohort (1372).