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Routine quantification of platelet-derived extracellular vesicles (PL-EVs) may be useful in the quality control (QC) of platelet concentrates (PCs). The aim of this multicenter study was to establish and validate a consensus protocol for the standardized PL-EV quantification using conventional flow cytometers.Eighty-six PCs were investigated in five blood transfusion centers (A-E) on Days 0 and 5. The centers used different apheresis instruments: Trima Accel (n = 56) and/or Amicus (n = 30). PCs were prepared using standard methods (sd-PCs; n = 73; A-D) or with pathogen inactivation (PI [PI-PCs]; n = 13; E). Platelet (PLT) count was determined using conventional hematology analyzers. PLT degranulation (P-selectin expression in response to thrombin receptor PAR1 activation) and PL-EVs were analyzed by flow cytometry.During storage, PLT count remained stable in 58 PCs (A, C, E), whereas a decrease was observed in 12 PCs (B). PLT degranulation declined in all PCs (p < 0.001) and PL-EVs increased in 74 PCs (A, C-E; p < 0.001). Certain donor variables (e.g., plasma cholesterol, immature PLT fraction) were associated with lower PL-EVs. In Trima-produced PCs, PL-EVs were significantly lower (D) and PLT degranulation was superior compared to PCs prepared with the Amicus (A, D). PL-EVs were 10-fold lower in PI-PCs, compared to sd-PCs. However, similar QC trends were demonstrated for both PC groups during storage.PL-EV analysis in a QC program of PCs was successfully performed with results comparable among the different centers. PLT degranulation and vesiculation were primarily affected by preparation techniques.