[Study of hemostasis in patients with a recent thromboembolic complication]

The clinical history of well-documented personal or familial episodes of thromboembolism with systematic construction of a genealogical tree orients the diagnosis of hereditary or acquired thrombophilia. The presence of favorable medical or surgical conditions for pulmonary embolism (surgical operation, prolonged bed rest, oral contraception, pregnancy, etc) are commonly observed in thrombophilia. Young age, under 40, at the time of the first episode, the recurrent nature of thromboses and a positive family history are three criteria in favour of the diagnosis of hereditary thrombophilia. Laboratory tests should be performed, if possible anticoagulant therapy, or taking into account its effect on the results, heparin reducing the antithrombin level and the oral anticoagulants those of proteins C and S and affecting the "classical" test of resistance to activated protein C. This abnormality is observed in nearly 20% of patients with previous thromboembolism in familial thrombophilia whereas it is twice less common in deficits of antithrombin, protein C and protein S. The other more or less acknowledged causes, alteration of plasminogen, dysfibrinogenaemia, homocysteinaemia, particular blood diseases, indicating systematic association of a full blood count with blood clotting tests, are much more rare. Of the acquired thrombophilias, the commonest is the presence of circulating anticoagulant and/or anticardiolipine antibodies, these two conditions also requiring systematic investigation. Biological examinations for determining the cause of unexpected pulmonary embolism is essential but should not delay instauring treatment. It should be associated with a familial enquiry if the patient has a hereditary thrombophilia. Interpretation of the results should obey the rule of the 3 cs: is the biological abnormality the cause, a coincidence or the consequence of the affection?