Fig 2: The ability of COVID19 plasma to activate platelets is increased for patients with high circulating levels of ferritin and at timepoints preceding a thrombotic event.A) Plasma from COVID-19 inpatient, COVID-19 convalescent and healthy donors was incubated with platelets isolated from healthy volunteers. The gMFI levels of CD63, CD62P, CD32 and C3aR are shown in these three groups. Kruskal-Wallis non-parametric testing was used to compare all three groups and pair-wise comparisons were also performed; p-values are depicted. B) Spearman correlation of the gMFI surface levels of the markers used in (A) and selected clinical parameters of the COVID-19 inpatient group. r correlation coefficient shown on the key (right). Asterisks *, ** and *** denote p values less than 0.05, 0.01 and 0.001 respectively. Highlighted squares denote FDR values less than 0.05. C) Representative scatter plots for ferritin with CD63, CD32 and C3aR. D) CD63 gMFI surface levels of control platelets induced by plasma derived from COVID-19 patients with thrombosis drawn at different timepoints relative to the thrombotic event. E) CD63 gMFI surface levels of control platelets induced by plasma derived from COVID-19 patients prior to thrombosis and after thrombosis, COVID-19 patients without thrombosis and COVID-19 patients in convalescence.