Involvement of externalized PS in SS MP binding to ECs. Concentration (A-B), PS exposure (C-D), and size (E-F) of SS PLT-MPs and SS RBC-MPs were determined after a 60-minute incubation with (EC+) or without (EC−) ECs (n = 17 patients per bar). *P < .05, **P < .01 vs EC−, Wilcoxon test. FS, forward scatter.