title: Prediction of recurrent venous thromboembolism by the activated partial thromboplastin time.
abstract: BACKGROUND
  Venous thromboembolism (VTE) is a multi-factorial disease. Extensive thrombophilia screening is costly and often inconclusive. Simple laboratory methods are required to predict the risk of recurrence.
  
  
  OBJECTIVE
  To assess if measurement of activated partial thromboplastin time (APTT) allows stratification of patients with VTE into high- and low-risk categories with regard to recurrence.
  
  
  METHODS
  We prospectively followed 918 patients with a first unprovoked VTE and studied the relationship between recurrence and an APTT after discontinuation of anticoagulation. APTT was expressed as a ratio of test to reference coagulation times. Study endpoint was symptomatic recurrent VTE.
  
  
  RESULTS
  Venous thromboembolism recurred in 101 (11%) patients. Patients without recurrence had a greater APTT ratio than those with recurrence (0.97 +/- 0.09 vs. 0.93 +/- 0.09, P = 0.001). After 4 years, probability of recurrent VTE was 8.5% (95% CI: 5.5-11.5%) among patients with a ratio equal to or > 0.95 and 15.6% (95% CI: 11.4-19.9%) among patients with a lower ratio (P = 0.005). Compared with patients with an APTT ratio < 0.95, the relative risk (RR) of recurrence among patients with a ratio equal to or > 0.95 was 0.56 (95% CI: 0.38-0.84, P = 0.005) before and 0.58 (95% CI: 0.39-0.87, P = 0.009) after adjustment for sex, age, factor V Leiden, and factor II G20210A.
  
  
  CONCLUSIONS
  Measurement of APTT allows stratification of patients with VTE into high- and low-risk categories with regard to recurrence.
authors.affiliation: Department of Internal Medicine I, Medical University of Vienna, Vienna, Austria.
authors.forename: G
authors.initials: G
authors.lastname: Hron
authors.forename: S
authors.initials: S
authors.lastname: Eichinger
authors.forename: A
authors.initials: A
authors.lastname: Weltermann
authors.forename: P
authors.initials: P
authors.lastname: Quehenberger
authors.forename: W M
authors.initials: WM
authors.lastname: Halbmayer
authors.forename: P A
authors.initials: PA
authors.lastname: Kyrle
mesh_terms: D000328:Adult; D000368:Aged; D000925:Anticoagulants / Q000627:therapeutic use; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010314:Partial Thromboplastin Time; D011446:Prospective Studies; D012008:Recurrence; D012306:Risk; D019851:Thrombophilia / Q000097:blood / Q000175:diagnosis; D016896:Treatment Outcome; D020246:Venous Thrombosis / Q000175:diagnosis* / Q000517:prevention & control*
chemical_list: D000925:Anticoagulants