Deep vein thrombosis: idiopathic: 3 months of anticoagulation was not clearly as better than 12 months

Clinical bottom line (level 1b-)

  1. Patients with a first idiopathic deep vein thrombosis who stop anticoagulation at 3 months compared with 1 year were not clearly less likely to have a recurrent venous thromboembolism, a major bleed or die.
Agnelli et al: N Engl J Med 2001; 345 : 165-169
Expires May 2004

The study

Single-blinded ?concealed randomised trial with intention-to-treat
Setting: 10 anticoagulation clinics, Italy

267 patients (aged mean 67, 58% male) with a first idiopathic proximal deep vein thrombosis who had taken oral anticoagulants (adjusted so INR 2.0 to 3.0) for 3 months

Excluded if
  • aged < 15, > 85
  • need for longterm anticoagulants
  • major psychiatric disorders
  • life expectancy < 2 years
  • unable to be followed-up
  • recurrence of venous thromboembolism or episode of bleeding in first 3 months
  • known cause for DVT: cancer, known thrombophilia, recent immobilisation for > 7 days, recent trauma or surgery within 3 months, pregnancy, recent childbirth or use of oral contraceptives

Control Group: (n = 133, 133 analysed): stop anticoagulation at 3 months
Experimental Group: (n = 134, 134 analysed): continue anticoagulation to a total of 12 months

100% followed for 2 years
Outcome notes:
  • major bleeding : clinically overt and a fall in Hb of at least 2 g/dl or need for tranfusion ot 2 or more units of red cells; retroperitoneal or intracranial or required permanent discontinuation of study drug

The evidence

Outcome Time to outcome CER EER RRR
(95% CI)		 ARR
(95% CI)		 NNT
(95% CI)
recurrent venous thromboembolism 2 years 21
(15.8%)		 21
(15.7%)		 1%
(-73% to 43%)		 0.12%
(-8.62% to 8.85%)		 850
(NNT = 11 to infinity;
NNH = 12 to infinity)
major bleeding 2 years 2
(1.50%)		 4
(2.99%)		 -99%
(-970% to 63%)		 -1.48%
(-5.03% to 2.07%)		 -68
(NNT = 48 to infinity;
NNH = 20 to infinity)
death 2 years 7
(5.26%)		 7
(5.22%)		 1%
(-180% to 64%)		 0.04%
(-5.31% to 5.39%)		 2500
(NNT = 19 to infinity;
NNH = 19 to infinity)

Citation

  1. Agnelli G, Prandoni P, Santamaria MG, et al: three months versus one year of oral anticoagulant therapy for idiopathic deep venous thrombosis. N Engl J Med 2001; 345 : 165-169
Search Terms: from ACP Journal Club
Contributor: , May 2002
Reviewer:

Clinical Question.
Patient first idiopathic deep vein thrombosis
Intervention or Exposure 12 months of anticoagulation
Comparison 3 months of anticoagulation
Outcome recurrent venous thromboembolism, major bleeding, death