LABORATORY APPROACH TO BLOOD-COAGULATION DEFECTS IN PATIENTS WITH DEEP VENOUS THROMBOSIS

Thrombophilia is characterized by an inherited or acquired defect in t he blood coagulation pathway lending to an increased risk for thrombos is. The etiological approach following confirmed venous thrombotic eve nts should rule out medical or chirurgical risk factors. Thrombophilia should be sought by laboratory tests. The recent discovery of a blood coagulation defect : inherited resistance to activated protein C whic h is found to 20 % of patients with former thrombotic events has chang ed current laboratory approach. Deficiencies of one of the anticoagula nt proteins (antithrombin III, protein C, protein S) are found in 10 % of the patients, similar to the frequency of antiphospholipid antibod ies. These tests may be difficult to interpret immediately after the t hrombotic event because of various factors such as inflammatory states or anticoagulant treatments. Therefore this abnormal tests should be confirmed on a later sample analysis far from the event. The discovery of an inherited blood coagulation pathway defect may affect the durat ion of treatment, prophylaxis in situations with circumstantial risk f actors and requires familial analysis. Inherited resistance to activat ed protein C may be associated with another inherited defect leading t o an increased risk for thrombosis (J Mal Vasc 1996, 21 : pages 1-6).