Comparison of the efficacy and safety of low molecular weight heparins and unfractionated heparin in the initial treatment of deep venous thrombosis. An updated meta-analysis.

The aim of this study was to determine whether treatment with low molecular weight heparin (LMWH) reduces the incidence of recurrent thromboembolic events, death, haemorrhages, and extension of thrombus more than treatment with unfractionated heparin (UFH) in patients with established deep vein thrombosis (DVT). The study design was an updated meta-analysis of results from 20 randomised controlled clinical studies comparing LMWH with UFH. The main outcomes measured included i) the incidence of thromboembolic events (DVT and/or pulmonary embolism): ii) the incidence of major haemorrhages; iii) total mortality; and iv) extension of thrombus. Statistically significant reductions in favour of LMWH were observed for mortality [common odds ratio (OR) 0.70, 95% confidence interval (CI) 0.50 to 0.98; p = 0.035]. major haemorrhage (common OR 0.59, 95% CI 0.35 to 0.98; p = 0.042) and thrombus extension (common OR 0.65, 95% CI 0.44 to 0.96; p = 0.03). A nonsignificant trend, also in favour of LMWH, was observed for the recurrence of venous thromboembolic events (common OR 0.77, 95% CI 0.55 to 1.08; p = 0.13). The results from the meta-analysis showed that LMWHs seem to have a higher benefit/risk ratio than UFH in the treatment of venous thrombosis.