PROS1 and COVID-19: COVID-19 convalescent plasma contained more protein C antigen than standard fresh frozen plasma but was otherwise not different for any coagulation measures including prothrombin time, activated partial thromboplastin time, thrombin time, fibrinogen, D-dimer, von Willebrand factor activity, von Willebrand factor antigen, coagulation factors II, V, VII–XII, protein S activity, and alpha-2 plasmin inhibitor (Table 2; Fig. 1).