PF4 and hemophilia: The study also found that patients with hemophilia displayed elevated plasma concentrations of platelet activation markers platelet factor 4 (PF4), chemokine ligand 7 (CXCL7), and RANTES (Regulated upon Activation, Normal T Cell Expressed, and Presumably Secreted), with vWF concentrations being raised in those with severe hemophilia A. Among those with severe hemophilia, platelet activation was found to be correlated with FVIII consumption, indicating that platelet activation is up-regulated in the presence of secondary hemostasis deficiency [24].