Clinical and biochemical risk factors for first and recurrent episodes of venous thrombosis

Abstract

The objectives of this thesis were to study the magnitude of the risk of venous thrombosis (VT) in the general population, and to determine clinical and biochemical factors that influence this risk. We examined this separately for first and for recurrent thrombotic events: TROL, a Norwegian prospective follow-up study in the population, in which we counted patients with a 1st event of VT and LETS, a follow-up of a Dutch cohort of 474 consecutive patients with a 1st objectively confirmed VT. The incidence rates for all first VT events was 1.43 per 1000 person-years and increased exponentially with age, and were slightly higher in women than in men. Patients with pre-existing inflammation or anticardiolipin antibodies did not have any increased risk for subsequent VT disease. We found that high levels of homocysteine are at most a weak risk factor for subsequent VT. In the LETS-study, the rate of VT recurrence was 25.9 per 1000 patient-years. The risk of recurrence was 2.7 times higher in men than in women. Recurrence risk was increased if the initial VT was unprovoked or if women used oral contraceptives during follow-up. Surprisingly, there was no clear relation between recurrence risk and the presence of thrombophilia