The risk of recurrent venous thromboembolism in patients with inherited deficiency of natural anticoagulants antithrombin, protein C and protein S.

Few data are available on the risk of recurrent venous thromboembolism (VTE) associated with the rare inherited deficiencies of natural anticoagulants. We studied 602 patients with previous VTE: the incidence of first recurrence in the absence of anticoagulation was retrospectively estimated in 64 patients with deficiency of antithrombin (AT, n=14), protein C (PC, n=28), or protein S (PS, n=22) and 538 with no known defect, who acted as the reference group. After adjustment for sex, age, and circumstances of the first event, AT deficiency resulted an independent risk factor for recurrence (hazard ratio 1.9, 95% CI 1.0-3.9); the carriers of PC or PS deficiency had a marginal increase in risk (hazard ratio 1.4, 95% CI 0.9-2.2). In conclusion, patients with AT deficiency are potential candidates for long-term oral anticoagulation.