New oral anticoagulants for preventing venous thromboembolism

Orthopaedic surgery is known to be associated with a high risk of venous thromboembolism, and prophylaxis for orthopaedic patients is vital. In the linked systematic review and meta-analysis (doi:10.1136/bmj.e3675), Gómez-Outes and colleagues present a comparative effectiveness review that examines newer anticoagulant agents (dabigatran, rivaroxaban, and apixaban) in the prevention of venous thromboembolism after hip or knee replacement surgery.1

This review used randomised controlled trials that had directly compared one of the newer agents with enoxaparin to indirectly compare the effects of these drugs on venous thromboembolism outcomes and clinically relevant bleeding. The review therefore gives us an idea of what the results of a head to head trial would be like. This type of network meta-analysis in which multiple treatments are compared using both direct comparisons of interventions within randomised controlled trials and indirect comparisons across trials on the basis of a common comparator is on the methodological cutting edge of systematic reviews, but it can be fraught with peril if not done with scientific rigour.2 It found that rivaroxaban led to significantly lower rates of symptomatic venous thromboembolism than enoxaparin but at the cost of significantly increased bleeding. Both apixaban and dabigatran were as effective as enoxaparin in preventing venous thromboembolism, but apixaban …