OBJECTIVETo investigate the prevalence and the risk of natural anticoagulants such as plasma protein C (PC), protein S (PS) and antithrombin (AT) deficiency in thromboembolic patients with no evident acquired factors.

METHODSClotting assays on French STAGO autoanalyzer were used to detect the activity of plasma PC, PS and AT in 85 patients with thrombotic disease and 50 sex and age matched healthy controls.

RESULTSAmong the 85 enrolled patients (18 arterial and 67 venous thromboembolism), male to female ratio was 1.4 and the median age was 42 years (17-69). The activity of plasma PC, PS and AT in the pre-therapy thrombotic disease group, the thrombo-recurrence group, and the age < or = 45 years group were significantly lower than that is the healthy control group, the first thrombotic episodes group and the age > 45 years group respectively (P < 0.001, P < 0.01, P < 0.01). The overall deficiency rate of these three natural anticoagulants was 30.6%, PS deficiency was the commonest (10.6%), the second was PC deficiency (8.2%), AT deficiency and combined deficiency each accounted for 5.9%.

CONCLUSIONThe PC, PS and AT protein deficiencies are frequent in Chinese thromboembolic patients, they are the independent risk factors for the thrombotic events and recurrence.