Alpha2-plasmin inhibitor (A2PI) is the main physiological inhibitor of plasmin. In the final phase of coagulation, activated factor XIII (FXIIIa) cross-links A2PI to fibrin and it has been shown that only cross-linked A2PI can efficiently inhibit fibrinolysis. After secretion into the plasma, full length A2PI contains a C-terminal plasminogen-binding site (PB-A2PI), which is lost due to cleavage by an as yet unknown protease. The truncated form (NPB-A2PI) remains enzymatically active, but it is a slow plasmin inhibitor. FXIIIa primarily cross-links PB-A2PI to fibrin. The binding of the truncated form to the clot and the effect of the ratio of the two C-terminal forms on the incorporation of PB-A2PI have not yet been investigated in detail. The study aims to investigate the incorporation of PB-A2PI and NPB-A2PI into the plasma clots of controls and patients with venous thromboembolism (VTE).