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Original Article
Volume 332:1661-1665 June 22, 1995 Number 25
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A Comparison of Six Weeks with Six Months of Oral Anticoagulant Therapy after a First Episode of Venous Thromboembolism
Sam Schulman, M.D., Ann-Sofie Rhedin, M.D., Per Lindmarker, M.D., Anders Carlsson, M.D., Gerd Lärfars, M.D., Peter Nicol, M.D., Enno Loogna, M.D., Else Svensson, M.D., Bengt Ljungberg, M.D., Hans Walter, M.D., Stanka Viering, M.D., Sune Nordlander, M.D., Barbro Leijd, M.D., Kjell-Åke Jönsson, M.D., Martin Hjorth, M.D., Olle Linder, M.D., Jonas Boberg, M.D., for The Duration of Anticoagulation Trial Study Group

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ABSTRACT

Background The optimal duration of oral anticoagulant therapy after a first episode of venous thromboembolism is still a matter of debate.

Methods We performed a multicenter trial comparing six weeks of oral anticoagulant treatment with six months of such therapy in patients who had a first episode of venous thromboembolism. Anticoagulant therapy consisted of warfarin or dicumarol. Of the 902 patients enrolled, 5 were later excluded because they had congenital protein C deficiency; 443 were randomly assigned to receive six weeks of oral anticoagulant therapy with a targeted international normalized ratio (INR) of 2.0 to 2.85, and 454 were randomly assigned to receive six months of such therapy. The initial diagnoses were confirmed by means of venography in cases of deep-vein thromboses (n = 790) and with perfusion–ventilation scanning or angiography in cases of pulmonary embolism (n = 107); recurrences were confirmed in the same way.

Results After two years of follow-up, there had been 123 recurrences of venous thromboembolism that met the diagnostic criteria, 80 in the six-week group (18.1 percent; 95 percent confidence interval, 14.5 to 21.6) and 43 in the six-month group (9.5 percent; 95 percent confidence interval, 6.8 to 12.2). The odds ratio for recurrence in the six-week group was 2.1 (95 percent confidence interval, 1.4 to 3.1). There was no difference in mortality or the rate of major hemorrhage between the six-week and six-month groups.

Conclusions Six months of prophylactic oral anticoagulation after a first episode of venous thromboembolism led to a lower recurrence rate than did treatment lasting for six weeks. The difference between the two groups occurred between 6 weeks and 6 months after the start of treatment, and the rates of recurrence remained nearly parallel for 11/2 years thereafter.


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From the Departments of Internal Medicine at Karolinska Hospital, Stockholm (S.S., P.L.), Huddinge Hospital, Huddinge (A.-S.R.), Danderyd Hospital, Danderyd (A.C.), Södersjukhuset, Stockholm (G.L.), Köping Hospital, Köping (P.N.), Nacka Hospital, Stockholm (E.L.), Södertälje Hospital, Södertälje (E.S.), Nyköping Hospital, Nyköping (B. Ljungberg), Sabbatsberg Hospital, Stockholm (H.W.), Norrtälje Hospital, Norrtälje (S.V.), Central Hospital, Västerås (S.N.), St. Göran Hospital, Stockholm (B. Leijd), Linköping Regional Hospital, Linköping (K.-Å.J.), Lidköping Hospital, Lidköping (M.H.), Örebro Regional Hospital, Örebro (O.L.), and Uppsala Academic Hospital, Uppsala (J.B.) — all in Sweden.

Address reprint requests to Dr. Schulman at the National Hemophilia Center, Sheba Medical Center, Tel-Hashomer IL-52621, Israel.

Full Text of this Article


Related Letters:

Duration of Anticoagulant Therapy for Venous Thrombosis
Safavi K., Shojania A. M., Schulman S., The Duration of Anticoagulation Trial Study Group , Hirsh J.
Extract | Full Text  
N Engl J Med 1995; 333:1288-1289, Nov 9, 1995. Correspondence

Venous Thromboembolism
Block J. A., White T. M., Fetrow C.W., Schulman S., The Duration of Anticoagulation Trial Study Group , Diuguid D. L.
Extract | Full Text  
N Engl J Med 1997; 337:51-53, Jul 3, 1997. Correspondence

Venous Thromboembolism and Cancer
Eikelboom J. W., Mehta S. R., Hughes-Davies T.H., Roychowdhury D., Zacharski L. R., Ornstein D. L., Schulman S., Lindmarker P.
Extract | Full Text  
N Engl J Med 2000; 343:1337-1338, Nov 2, 2000. Correspondence

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