<P> Tissue plasminogen activator (t - PA) and urokinase are the agents that convert plasminogen to the active plasmin, thus allowing fibrinolysis to occur . t - PA is released into the blood very slowly by the damaged endothelium of the blood vessels, such that, after several days (when the bleeding has stopped), the clot is broken down . This occurs because plasminogen became entrapped within the clot when it formed; as it is slowly activated, it breaks down the fibrin mesh . t - PA and urokinase are themselves inhibited by plasminogen activator inhibitor - 1 and plasminogen activator inhibitor - 2 (PAI - 1 and PAI - 2). In contrast, plasmin further stimulates plasmin generation by producing more active forms of both tissue plasminogen activator (tPA) and urokinase . </P> <P> Alpha 2 - antiplasmin and alpha 2 - macroglobulin inactivate plasmin . Plasmin activity is also reduced by thrombin - activatable fibrinolysis inhibitor (TAFI), which modifies fibrin to make it more resistant to the tPA - mediated plasminogen . </P> <P> When plasmin breaks down fibrin, a number of soluble parts are produced . These are called fibrin degradation products (FDPs). FDPs compete with thrombin, and thus slow down clot formation by preventing the conversion of fibrinogen to fibrin . This effect can be seen in the thrombin clotting time (TCT) test, which is prolonged in a person that has active fibrinolysis . </P> <P> FDPs, and a specific FDP, the D - dimer, can be measured using antibody - antigen technology . This is more specific than the TCT, and confirms that fibrinolysis has occurred . It is therefore used to indicate deep - vein thrombosis, pulmonary embolism, DIC and efficacy of treatment in acute myocardial infarction . Alternatively, a more rapid detection of fibrinolytic activity, especially hyperfibrinolysis, is possible with thromboelastometry (TEM) in whole blood, even in patients on heparin . In this assay, increased fibrinolysis is assessed by comparing the TEM profile in the absence or presence of the fibrinolysis inhibitor aprotinin . Clinically, the TEM is useful for near real - time measurement of activated fibrinolysis for at - risk patients, such as those experiencing significant blood loss during surgery . </P>

Test used to identify the presence of fibrinolysis