title: Oral anticoagulation strategies after a first idiopathic venous thromboembolic event.
abstract: OBJECTIVE
  The optimal duration and intensity of warfarin therapy after a first idiopathic venous thromboembolic event are uncertain. We used decision analysis to evaluate clinical and economic outcomes of different anticoagulation strategies with warfarin.
  
  
  METHODS
  We built a Markov model to assess 6 strategies to treat 40- to 80-year-old men and women after their first idiopathic venous thromboembolic event: 3-month, 6-month, 12-month, 24-month, and unlimited-duration conventional-intensity anticoagulation (International Normalized Ratio, 2-3) and unlimited-duration low-intensity anticoagulation (International Normalized Ratio, 1.5-2). The model incorporated age- and sex-specific clinical parameters, utilities, and costs. Using a societal perspective, we compared strategies based on quality-adjusted life-years (QALYs), lifetime costs, and incremental cost-effectiveness ratios.
  
  
  RESULTS
  In our baseline analysis, incremental cost-effectiveness ratios were lower in younger patients and in men, reflecting the higher bleeding risk at older ages, and the lower risk of recurrence among women. Based on a willingness-to-pay of <$50000/QALY, the 24-month strategy was most cost-effective in 40-year-old men ($48805/QALY), while the 6-month strategy was preferred in 40-year-old women ($35977/QALY) and 60-year-old men ($29878/QALY). In patients aged >/=80 years, 3-month anticoagulation was less costly and more effective than other strategies. Cost-effectiveness results were influenced by the risks associated with recurrent venous thromboembolism, the major bleeding risk of conventional-intensity anticoagulation and the disutility of taking warfarin.
  
  
  CONCLUSIONS
  Longer initial conventional-intensity anticoagulation is cost-effective in younger patients while 3 months of anticoagulation is preferred in elderly patients. Patient age, sex, clinical factors, and patient preferences should be incorporated into medical decision making when selecting an appropriate anticoagulation strategy.
authors.affiliation: Division of General Internal Medicine, Department of Medicine, University of Pittsburgh, Pennsylvania, USA. aujesky@swissonline.ch
authors.forename: Drahomir
authors.initials: D
authors.lastname: Aujesky
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Smith
authors.forename: Mark S
authors.initials: MS
authors.lastname: Roberts
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000008:administration & dosage*; D003362:Cost-Benefit Analysis; D003661:Decision Support Techniques; D005260:Female; D006801:Humans; D008297:Male; D008390:Markov Chains; D008875:Middle Aged; D011655:Pulmonary Embolism / Q000517:prevention & control*; D011788:Quality of Life; D055502:Secondary Prevention; D020246:Venous Thrombosis / Q000517:prevention & control*; D014859:Warfarin / Q000008:administration & dosage*
chemical_list: D000925:Anticoagulants; D014859:Warfarin