Major bleedings in the comparisons between low-molecular weight heparin versus oral anticoagulant therapy for venous thromboembolism.

To evaluate the safety (major bleedings) of long-term treatment of symptomatic venous thromboembolism (VTE) using low molecular weight heparin (LMWH) compared with oral anticoagulant therapy (OAT) given for at least 3 months, we analyzed 10 randomized clinical trials enrolling a total of 2817 patients with objectively diagnosed symptomatic deep vein thrombosis, pulmonary embolism or both. The relative risk (RR, incidence of recurrent symptomatic VTE) was combined across the studies, using the inverse variance and the Mantel-Haenszel method. During treatment, major bleeding complications occurred in 2.8% of the patients in the LMWH arm versus 4% in the OAT arm: no statistically significant difference was observed (p=0.31). No differences in major bleeding were registered in the additional 3-9 months of follow-up (p=0.98). Long-term treatment with LMWH does not seem to be significantly safer than OAT. However, no conclusive interpretation from different studies with different designs is possible.