TF and COVID-19: platelet aggregation, thrombus volume, morphology, and contraction score were comparable between groups for collagen + TF (NS) and markedly reduced in COVID-19 vs. control for collagen (p < 0.0001)stable thrombus formation in COVID-19 patients, thrombi increased in number but smaller in individual size vs. control (p < 0.05); without external TF, no differences in platelet aggregation and thrombus volume in COVID-19 patients vs. control (NS)