Randomised controlled trials (RCTs) comparing the incidence of asymptomatic DVT in hospitalised medical patients receiving anticoagulant prophylaxis versus no prophylaxis were eligible for inclusion in the review. Studies had to assess all patients using a reliable screening method for DVT, such as venography or venous ultrasound. Studies were excluded if they assessed mechanical methods of prophylaxis (including compression stockings) or if patients received co-administered prophylactic antithrombotic drugs such as aspirin. Other eligible outcomes included the incidence of proximal DVT, all-cause mortality and major bleeding.
Included studies assessed commonly used single daily subcutaneous doses of low molecular weight heparins (LMWH; dalteparin, nadroparin and enoxaparin) or fondaparinux compared with subcutaneously administered placebo. The majority of included patients had various acute medical conditions. One study included only patients with acute decompensated chronic obstructive pulmonary disease (COPD). Another study included patients with congestive heart failure. Treatment periods were mainly between six and 14 days in duration, with follow-up periods lasting between 21 and 110 days.
Two reviewers independently assessed each study for inclusion.