Study designs of evaluations included in the review
Randomised, controlled trials (RCTs) with at least 2 months' follow-up were eligible.
Specific interventions included in the review
Studies evaluating low molecular weight heparin (LMWH) versus adjusted-dose unfractionated heparin (UFH) were eligible. The LMWH included dalteparin (200 or 240 IU/kg per day), certoparin (various doses), nadroparin (184 IU/kg per day), enoxaparin (200 IU/kg per day), reviparin (160 IU/kg per day) and bemiparin (115 IU/kg per day). LMWH was often given subcutaneously and UFH intravenously. The duration of heparin treatment ranged from 5 to 28 days. Most of the studies also provided oral anticoagulation for at least 3 months.
Participants included in the review
Studies of patients with acute venographically diagnosed deep vein thrombosis (DVT) were included.
Outcomes assessed in the review
Eligible studies had to objectively assess the incidence of recurrent VTE. Thrombus regression was also assessed. Recurrent DVT was confirmed by Doppler ultrasound or venography, and recurrent pulmonary embolism by ventilation perfusion lung scanning or arteriography. The outcome definitions used by the primary studies were accepted. The duration of follow-up ranged from 2 to 6 months.
How were decisions on the relevance of primary studies made?
Two independent reviewers selected the studies, but the authors did not state how any disagreements were resolved.