Decision analysis model of prolonged oral anticoagulant treatment in factor V Leiden carriers with first episode of deep vein thrombosis.

OBJECTIVE

To assess the risks and benefits of oral anticoagulant treatment extended beyond 3 months after a first episode of deep vein thrombosis in patients who carry factor V Leiden mutation. Such patients have over twice the risk of recurrence after the recommended treatment period, but more information is required before widespread genetic screening can be recommended.

DESIGN

A decision analysis Markov model (with data extracted form literature) representing the risks of developing symptomatic venous thromboembolism, the risks of major bleeding, and the efficacy of anticoagulant treatment.

SUBJECTS

A hypothetical cohort of 1000 carriers of factor V Leiden recovering from a first episode of deep vein thrombosis in the lower limbs.

MAIN OUTCOME MEASURES

Risks and benefits of, firstly, stopping oral anticoagulation 3 months after first episode of thrombosis with reinitiation of treatment only after recurrent thrombosis and, secondly, extension of oral anticoagulation up to 1 to 5 years.

RESULTS

Despite consistent biases in favour of extended oral anticoagulation, analysis revealed that among factor V carriers the number of major haemorrhages induced by oral anticoagulants would exceed that of clinical pulmonary emboli prevented over the entire range of duration of anticoagulation (1 to 5 years). On the other hand, the number of recurrent deep vein thrombi prevented would exceed that of iatrogenic major bleedings.

CONCLUSION

The lack of evidence of a net clinical benefit of prolonged oral anticoagulation, at least beyond 1 year, among patients recovering from acute deep vein thrombosis does not support the decision to promote widespread genetic screening programmes to detect the factor V mutation.