Elevated platelet biogenesis during sepsis progression. Characteristics of patients with sepsis (S) are displayed at the following time points: I: admission day; II: day 5 to 7; and III: day of ICU discharge. (A) Platelet count. (B) Reticulated platelets indicated as TO-positive fraction were assessed by flow cytometry. (C) TPO levels in sepsis plasma were determined by ELISA. (D) Mean platelet volume. (E) Main platelet receptor and integrin expression were analyzed by flow cytometry in patients and corresponding healthy controls (HC). (F-I) Platelet (pre-)activation due to P-selectin exposure (CD62P) (F-G) and integrin αIIbβ3 activation (H-I) were assessed in whole blood measured by flow cytometry. Representative curves are shown in panels F and H. (A,D) Reference ranges are shown as dashed lines. (A-I) Graphs show median ± IQR. Differences were analyzed using Wilcoxon matched-pairs signed rank test (A,C,D). Kolmogorov-Smirnov test (E). Kruskal-Wallis test (B, G, I). n.s., nonsignificant. *P < .05; **P < .01; ***P < .001; ****P < .0001. APC, allophycocyanin; FITC, fluorescein isothiocyanate; GEO-MFI, geometric mean fluorescence intensity; MPV, mean platelet volume; PLTs, platelets.