EV concentration according to preparation parameters in RBC units prepared at the BES (n = 648). (A) PEV and EEV counts according to filtration method. (B) PEV and EEV counts according to leukoreduction filter. White bars indicate WBf units, and gray bars indicate RBCf units. (C) PEV and EEV counts according to time for preparation, calculated as hours elapsed between blood donation and RBC unit preparation. Mean concentrations are shown for units prepared on the day of donation (D1, green bar) and for units prepared the day after donation (D2, purple bar). ***P < .0001, **P < .001, and *P < .05 according to Student t test. For all panels, each horizontal bar reports the mean, and each vertical bar represents the SD.