Study designs of evaluations included in the review
The included studies were non-randomised uncontrolled trials, and double-blind randomised controlled trials where one arm received combined ASA and any coumarin anticoagulant (e.g. warfarin), and another arm received either ASA or an anticoagulant as monotherapy. Trials published only in abstract form, and noncomparative trials (e.g. case series, uncontrolled trials), were excluded from the analyses. Trials were categorised as either A or B.
Category A trials were randomised, controlled and double-blind trials that used the INR to measure anticoagulation, and reported complete safety and efficacy data. Trials in this category were considered highly interpretable.
Category B trials were either of a suboptimal trial design (non-randomised or uncontrolled), or did not report complete interpretable efficacy and safety data. These included reported trials using non-INR anticoagulation measurement methods, and those providing inadequate information regarding target or achieved anticoagulation intensity. Trials in this category were considered to be less reliable than category A trials.
The follow-up periods ranged from 10 weeks to 7 years (excluding those studies focusing specifically on safety issues).
Specific interventions included in the review
The specific interventions were: warfarin (international normalised ratio, INR, 1.5 to 4.5); ASA (75 to 325 mg/day); ASA plus warfarin (various combinations of doses); acenocoumarin (prothrombin time, PT, 1.8 to 2.3 times); warfarin plus dipyridamole (PT 1.5 to 2.5 times); acenocoumarin (1.8 to 2.3 times) plus ASA (500 mg/day); ASA plus heparin and warfarin (various combinations of doses).
Participants included in the review
Patients undergoing antithrombic therapy for a variety of cardio and cerebrovascular conditions including: the prevention of stroke; the treatment of angina and myocardial infarction; the prevention of thrombosis after angioplasty, valve replacement and stent insertion; and the treatment of atherosclerosis.
Outcomes assessed in the review
Incidence of thromboembolism, embolic episodes, and major and minor bleeding were assessed.
How were decisions on the relevance of primary studies made?
The authors do not state how the papers were selected for the review, or how many of the authors performed the selection.