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

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Abstract
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. Patients who carry the factor V Leiden mutation have a more than twice the risk of recurrence after a first episode of deep vein thrombosis Before screening for the abnormality is advocated in all patients recovering from acute deep vein thrombosis, it should be determined whether carriers of the mutation would benefit from the diagnosis The risks (major haemorrhage) of extended oral anticoagulation beyond the usually recommended 3 month period would exceed its benefits, in terms of clinical pulmonary emboli prevented The decision to promote widespread screening programmes to detect factor V mutation should be questioned in the absence of clinical benefit provided by extended use of oral anticoagulants

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