COVID-19 induces a hyperactive phenotype in circulating platelets
Platelet dense granule release was measured in duplicate in severe (n = 5) and nonsevere (n = 4) COVID-19 patients compared to hospitalised (n = 3) and healthy controls (n = 6). Platelets were stimulated with 0.1 U/ml thrombin (A), 0.5 U/ml thrombin (B), 1 μM U46619 (C), and 6.6 μM U46619 (D) and ATP release (surrogate for ADP) was measured using a Chronolume luciferase assay. ADP release is expressed as pmol/106 platelets. Boxplots represent the data median (line inside the box) and the IQR (outline of the box) together with data maximum and data minimum (whiskers) and individual observations (see individual data in S1 Data). Statistical analysis was performed using a two-tailed t test and p-values were adjusted for multiple comparisons using a Holm–Bonferroni post hoc test. COVID-19, Coronavirus Disease 2019; IQR, interquartile range.