The Relationship of Plasma Fibrinogen ( Factor I ) Level to Fibrin Stabilizing Factor ( Factor Xffl ) Activity

T HE RECENTLY RECOGNIZED blood coagulation factor, Factor XIII, or fibrin stabilizing factor (FSF), is considered currently to be an macfive precursor which on activation by thrombin, in the presence of calcium ions, is changed to an active enzyme, a transamidase. The active principle acts through a transamidation process at the terminal stages of blood clotting to convert a soluble fibrin into tough, cross-linked, urea-insoluble, and ( presumably) a physiologically useful one.1’2’3 A hemorrhagic diathesis due to its congenital absence has been well documented.4’5 Reduced FSF activity, with or without hemorrhagic manifestations, in association with a variety of disease states has been reported.6’7 The relation of FSF activity to fibrinogen concentration was emphasized in the early studies of the mode of action of FSF.89 Furthermore, whereas lowered Factor XIII activity was reported in association with one case of hyperfibrmnogenemia,1#{176} the presence of normal amounts of FSF in the plasma and platelets of an afibrinogenemic individual was noted. The present study was undertaken to investigate the relationship of fibrinogen concentration to FSF activity in healthy subjects and patients with a variety of diseases.