Platelet apoptosis in COVID-19 patients. (A-C) Changes in apoptosis pathways were analyzed by assessing the depolarization of the ΔΨm (A), cytosolic calcium concentration (B), and PS externalization (C) in platelets from COVID-19 patients in the ICU or COVID-19 patients not in the ICU, as well as ICU non–COVID-19 patients (control group) and healthy donors, respectively. (D) Quantification of cleaved-caspase 9 level in platelets from COVID-19 patients in the ICU normalized to healthy donors. (E) Representative western blot showing GAPDH and cleaved-caspase 9 proteins in platelets from COVID-19 patients in the ICU. Protein bands were detected with the infrared imaging system (Odyssey, LI.COR, Lincoln, NE). (F) Diagram indicating the number of COVID-19 patients in the ICU positive for each apoptotic parameter: ΔΨm depolarization, cytosolic calcium concentration, and PS externalization. Data are presented as mean ± standard error mean (SEM) of the measured fold increase compared with control. Not significant, *P < .05, **P < .01, ***P < .001, ****P < .0001. The number of patients and healthy donors tested is reported in each graphic. Dashed lines represent the cutoffs determined from healthy donors as mean of fold increase (FI) + 2× SEM.