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3 months and 1 year of oral anticoagulant treatment were equivalent for idiopathic proximal deep venous thrombosis

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 QUESTION: In patients who have had a first episode of idiopathic proximal deep venous thrombosis, what is the long term effectiveness of extending to 1 year the initial 3 month course of oral anticoagulant treatment?


Randomised (unclear allocation concealment*), unblinded,* controlled trial with ≥ 2 years of follow up.


10 study centres in Italy.


267 patients (mean age 67 y, 58% men) who had a first episode of symptomatic idiopathic proximal deep venous thrombosis confirmed by compression ultrasonography or venography, and had completed 3 uninterrupted months of oral anticoagulant treatment without a recurrence of thromboembolism or bleeding. Exclusion criteria included anticoagulant treatment for reasons other than venous thromboembolism, major psychiatric disorders, life expectancy < 2 years, and inability to return for follow up. 90% of patients completed the study.


After 3 months of treatment with warfarin (97% of patients) or acenocoumarol, 133 patients were allocated to discontinue (3 mo treatment group) and 133 patients to continue (1 y treatment group) oral anticoagulant treatment for 9 additional months. The dose of the oral anticoagulant was adjusted to maintain an international normalised ratio of 2.0 to 3.0.

Main outcome measures

The …

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  • Source of funding: not stated.

  • For correspondence: Professor G Agnelli, Sezione de Medicina Interna e Cardiovascolare, Dipartimento di Medicina Interna, Università di Perugia, Via Enrico dal Pozzo, 06123 Perugia, Italy.

  • * See glossary.