title: Risk of post-thrombotic syndrome after subtherapeutic warfarin anticoagulation for a first unprovoked deep vein thrombosis: results from the REVERSE study.
abstract: BACKGROUND
  Risk factors for post-thrombotic syndrome (PTS) remain poorly understood.
  
  
  OBJECTIVE
  In this multinational multicenter study, we evaluated whether subtherapeutic warfarin anticoagulation was associated with the development of PTS.
  
  
  METHODS
  Patients with a first unprovoked deep venous thrombosis (DVT) received standard anticoagulation for 5-7 months and were then assessed for PTS. The time in the therapeutic range was calculated from the international normalized ratio (INR) data. An INR below 2, more than 20% of the time, was considered as subtherapeutic anticoagulation.
  
  
  RESULTS
  Of the 349 patients enrolled, 97 (28%) developed PTS. The overall frequency of PTS in patients with subtherapeutic anticoagulation was 33.5%, compared with 21.6% in those with an INR below two for ≤ 20% of the time (P = 0.01). During the first 3 months of therapy, the odds ratio (OR) for developing PTS if a patient had subtherapeutic anticoagulation was 1.78 (95% confidence interval [CI] 1.10-2.87). After adjusting for confounding variables, the OR was 1.84 (95% CI 1.13-3.01). Corresponding ORs for the full period of anticoagulation were 1.83 (95% CI 1.14-3.00) [crude] and 1.88 (95% CI 1.15-3.07) [adjusted].
  
  
  CONCLUSIONS
  Subtherapeutic warfarin anticoagulation after a first unprovoked DVT was significantly associated with the development of PTS.
authors: Centre for Clinical Epidemiology and Community Studies, Jewish General Hospital, Montréal, Canada.
authors: R S
authors: RS
authors: Chitsike
authors: M A
authors: MA
authors: Rodger
authors: M J
authors: MJ
authors: Kovacs
authors: M T
authors: MT
authors: Betancourt
authors: P S
authors: PS
authors: Wells
authors: D R
authors: DR
authors: Anderson
authors: I
authors: I
authors: Chagnon
authors: G
authors: G
authors: LE Gal
authors: S
authors: S
authors: Solymoss
authors: M A
authors: MA
authors: Crowther
authors: A
authors: A
authors: Perrier
authors: R H
authors: RH
authors: White
authors: L M
authors: LM
authors: Vickars
authors: T
authors: T
authors: Ramsay
authors: S R
authors: SR
authors: Kahn
mesh_terms: D000328:Adult; D000368:Aged; D000925:Anticoagulants / Q000008:administration & dosage*; D001777:Blood Coagulation / Q000187:drug effects*; D002170:Canada; D005060:Europe; D005260:Female; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D054070:Postthrombotic Syndrome / Q000097:blood / Q000175:diagnosis / Q000209:etiology*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome; D020246:Venous Thrombosis / Q000097:blood / Q000150:complications / Q000175:diagnosis / Q000188:drug therapy*; D014859:Warfarin / Q000008:administration & dosage*
chemical_list: D000925:Anticoagulants; D014859:Warfarin