305 unselected patients under long-term oral anticoagulation treatment for having presented one o more ep^L sodes of deep vein thrombosis and/or pulmonary embolism, have been studied for the following anomalies: Dysfibrinogenemia, Lupus anticoagulant, Antithrombin-III deficiency, Protein C, Protein S, Heparin Cofactor II, and anomalies in the fibrinolytic components t-PA PAI and Plasminogen. Protein C antigen and activity as well as free Protein S antigen levels have been related to those found in a control group at different intensities of oral anticoagulant
As shown in the table this study, performed on unselected patients from the clinical point of view, has not only confirmed the presence of a previously known congenital defect in 16 patients (5%) but also has per miteed the identification of a previously unkown de- -feet in 45 patients (15%)
Since the identification of a congenital abnormality permits to prevention of new thrombotic episodes and the identification of the afected members, these re- -suits support the convenience of performing such syste matic biological studies in patients suffering from thrombosis
