Estimation of fibrinolytic activity of whole blood in patients with recurrent idiopathic deep venous thrombosis.

The fibrinolytic activity of blood was measured in control subjects and patients with idiopathic deep venous thrombosis by a new method, which was based on the rate of release of radioactivity in vitro from clotted blood to which 125I-fibrinogen was previously added. Blood was obtained without application of a venous tourniquet. The results are expressed as the amount of fibrin lysed per unit of time and are not affected by the fibrinogen concentration, a drawback inherent in previous techniques. The mean value (+/- standard deviation) of fibrinolytic activity was 0.464 +/- 0.158 mg of fibrin lysed per hour in the control subjects and 0.194 +/- 0.089 mg of fibrin lysed per hour in the patients. This difference is significant (p less than 0.01) and indicates a considerable reduction in fibrinolytic activity in patients with idiopathic deep venous thrombosis. This has been demonstrated without the need to stimulate the release of plasminogen activator by applying a venous tourniquet as done in previous studies.