title: Aspirin for the prevention of recurrent venous thromboembolism: the INSPIRE collaboration.
abstract: BACKGROUND
  In patients with a first unprovoked venous thromboembolism (VTE) the risk of recurrent VTE remains high after anticoagulant treatment is discontinued. The Aspirin for the Prevention of Recurrent Venous Thromboembolism (the Warfarin and Aspirin [WARFASA]) and the Aspirin to Prevent Recurrent Venous Thromboembolism (ASPIRE) trials showed that aspirin reduces this risk, but they were not individually powered to detect treatment effects for particular outcomes or subgroups.
  
  
  RESULTS
  An individual patient data analysis of these trials was planned, before their results were known, to assess the effect of aspirin versus placebo on recurrent VTE, major vascular events (recurrent VTE, myocardial infarction, stroke, and cardiovascular disease death) and bleeding, overall and within predefined subgroups. The primary analysis, for VTE, was by intention to treat using time-to-event data. Of 1224 patients, 193 had recurrent VTE over 30.4 months' median follow-up. Aspirin reduced recurrent VTE (7.5%/yr versus 5.1%/yr; hazard ratio [HR], 0.68; 95% confidence interval [CI], 0.51-0.90; P=0.008), including both deep-vein thrombosis (HR, 0.66; 95% CI, 0.47-0.92; P=0.01) and pulmonary embolism (HR, 0.66; 95% CI, 0.41-1.06; P=0.08). Aspirin reduced major vascular events (8.7%/yr versus 5.7%/yr; HR, 0.66; 95% CI, 0.50-0.86; P=0.002). The major bleeding rate was low (0.4%/yr for placebo and 0.5%/yr for aspirin). After adjustment for treatment adherence, recurrent VTE was reduced by 42% (HR, 0.58; 95% CI, 0.40-0.85; P=0.005). Prespecified subgroup analyses indicate similar relative, but larger absolute, risk reductions in men and older patients.
  
  
  CONCLUSIONS
  Aspirin after anticoagulant treatment reduces the overall risk of recurrence by more than a third in a broad cross-section of patients with a first unprovoked VTE, without significantly increasing the risk of bleeding.
  
  
  BACKGROUND
  www.anzctr.org.au. Unique identifier: ACTRN12611000684921.
authors.affiliation: From the National Health and Medical Research Council Clinical Trials Centre, University of Sydney, Sydney, Australia (J.S., A.C.K., R.M.); the Division of Internal and Cardiovascular Medicine and Stroke Unit, Department of Internal Medicine, University of Perugia, Perugia, Italy (C.B., G.A.); the Population Health Research Institute, McMaster University, Hamilton, ON, Canada (J.W.E.); the Department of Cardiothoracic and Vascular Sciences, University of Padua, Padua (P.P.); and the Department of Haematology, South Eastern Area Laboratory Services (SEALS), Prince of Wales Hospital, Sydney, Australia (T.A.B.). john@ctc.usyd.edu.au.
authors.forename: John
authors.initials: J
authors.lastname: Simes
authors.affiliation: From the National Health and Medical Research Council Clinical Trials Centre, University of Sydney, Sydney, Australia (J.S., A.C.K., R.M.); the Division of Internal and Cardiovascular Medicine and Stroke Unit, Department of Internal Medicine, University of Perugia, Perugia, Italy (C.B., G.A.); the Population Health Research Institute, McMaster University, Hamilton, ON, Canada (J.W.E.); the Department of Cardiothoracic and Vascular Sciences, University of Padua, Padua (P.P.); and the Department of Haematology, South Eastern Area Laboratory Services (SEALS), Prince of Wales Hospital, Sydney, Australia (T.A.B.).
authors.forename: Cecilia
authors.initials: C
authors.lastname: Becattini
authors.affiliation: From the National Health and Medical Research Council Clinical Trials Centre, University of Sydney, Sydney, Australia (J.S., A.C.K., R.M.); the Division of Internal and Cardiovascular Medicine and Stroke Unit, Department of Internal Medicine, University of Perugia, Perugia, Italy (C.B., G.A.); the Population Health Research Institute, McMaster University, Hamilton, ON, Canada (J.W.E.); the Department of Cardiothoracic and Vascular Sciences, University of Padua, Padua (P.P.); and the Department of Haematology, South Eastern Area Laboratory Services (SEALS), Prince of Wales Hospital, Sydney, Australia (T.A.B.).
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Agnelli
authors.affiliation: From the National Health and Medical Research Council Clinical Trials Centre, University of Sydney, Sydney, Australia (J.S., A.C.K., R.M.); the Division of Internal and Cardiovascular Medicine and Stroke Unit, Department of Internal Medicine, University of Perugia, Perugia, Italy (C.B., G.A.); the Population Health Research Institute, McMaster University, Hamilton, ON, Canada (J.W.E.); the Department of Cardiothoracic and Vascular Sciences, University of Padua, Padua (P.P.); and the Department of Haematology, South Eastern Area Laboratory Services (SEALS), Prince of Wales Hospital, Sydney, Australia (T.A.B.).
authors.forename: John W
authors.initials: JW
authors.lastname: Eikelboom
authors.affiliation: From the National Health and Medical Research Council Clinical Trials Centre, University of Sydney, Sydney, Australia (J.S., A.C.K., R.M.); the Division of Internal and Cardiovascular Medicine and Stroke Unit, Department of Internal Medicine, University of Perugia, Perugia, Italy (C.B., G.A.); the Population Health Research Institute, McMaster University, Hamilton, ON, Canada (J.W.E.); the Department of Cardiothoracic and Vascular Sciences, University of Padua, Padua (P.P.); and the Department of Haematology, South Eastern Area Laboratory Services (SEALS), Prince of Wales Hospital, Sydney, Australia (T.A.B.).
authors.forename: Adrienne C
authors.initials: AC
authors.lastname: Kirby
authors.affiliation: From the National Health and Medical Research Council Clinical Trials Centre, University of Sydney, Sydney, Australia (J.S., A.C.K., R.M.); the Division of Internal and Cardiovascular Medicine and Stroke Unit, Department of Internal Medicine, University of Perugia, Perugia, Italy (C.B., G.A.); the Population Health Research Institute, McMaster University, Hamilton, ON, Canada (J.W.E.); the Department of Cardiothoracic and Vascular Sciences, University of Padua, Padua (P.P.); and the Department of Haematology, South Eastern Area Laboratory Services (SEALS), Prince of Wales Hospital, Sydney, Australia (T.A.B.).
authors.forename: Rebecca
authors.initials: R
authors.lastname: Mister
authors.affiliation: From the National Health and Medical Research Council Clinical Trials Centre, University of Sydney, Sydney, Australia (J.S., A.C.K., R.M.); the Division of Internal and Cardiovascular Medicine and Stroke Unit, Department of Internal Medicine, University of Perugia, Perugia, Italy (C.B., G.A.); the Population Health Research Institute, McMaster University, Hamilton, ON, Canada (J.W.E.); the Department of Cardiothoracic and Vascular Sciences, University of Padua, Padua (P.P.); and the Department of Haematology, South Eastern Area Laboratory Services (SEALS), Prince of Wales Hospital, Sydney, Australia (T.A.B.).
authors.forename: Paolo
authors.initials: P
authors.lastname: Prandoni
authors.affiliation: From the National Health and Medical Research Council Clinical Trials Centre, University of Sydney, Sydney, Australia (J.S., A.C.K., R.M.); the Division of Internal and Cardiovascular Medicine and Stroke Unit, Department of Internal Medicine, University of Perugia, Perugia, Italy (C.B., G.A.); the Population Health Research Institute, McMaster University, Hamilton, ON, Canada (J.W.E.); the Department of Cardiothoracic and Vascular Sciences, University of Padua, Padua (P.P.); and the Department of Haematology, South Eastern Area Laboratory Services (SEALS), Prince of Wales Hospital, Sydney, Australia (T.A.B.).
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Brighton
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000925:Anticoagulants / Q000627:therapeutic use*; D001241:Aspirin / Q000627:therapeutic use*; D004311:Double-Blind Method; D005260:Female; D005500:Follow-Up Studies; D006470:Hemorrhage / Q000453:epidemiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010975:Platelet Aggregation Inhibitors / Q000627:therapeutic use*; D012008:Recurrence; D012307:Risk Factors; D012737:Sex Factors; D016896:Treatment Outcome; D054556:Venous Thromboembolism / Q000517:prevention & control*; D014859:Warfarin / Q000627:therapeutic use*
chemical_list: D000925:Anticoagulants; D010975:Platelet Aggregation Inhibitors; D014859:Warfarin; D001241:Aspirin
keywords: aspirin; clinical trial; embolism; meta-analysis; prevention; thrombosis