Anticoagulant prophylaxis to prevent asymptomatic deep vein thrombosis in hospitalized medical patients: a systematic review and meta-analysis.

BACKGROUND The effect of anticoagulant prophylaxis on the prevention of deep vein thrombosis (DVT) should include an investigation of both clinical and subclinical DVT. We conducted a systematic review to determine whether anticoagulant prophylaxis reduces the risk of asymptomatic DVT compared to no prophylaxis in at-risk hospitalized medical patients. METHODS MEDLINE, EMBASE, and the Cochrane Library were searched through March 2007 for randomized trials of anticoagulant prophylaxis for the prevention of asymptomatic DVT, assessed by venogram or ultrasound. We assessed four outcomes: all asymptomatic DVT, asymptomatic proximal DVT, major bleeding and mortality. Random effects meta-analyses were performed and results were expressed using relative risk (RR) and 95% confidence intervals (95% CIs). RESULTS Four trials including 5516 patients were eligible. Our pooled analysis demonstrated that compared to placebo, anticoagulant prophylaxis was associated with a significantly lower risk of any asymptomatic DVT (RR 0.51; 95% CI 0.39-0.67) and asymptomatic proximal DVT (RR 0.45; 95% CI 0.31-0.65). Anticoagulant prophylaxis was associated with a significantly increased risk of major bleeding compared to placebo (RR 2.00; 95% CI 1.05-3.79). There was no significant difference in the pooled estimate for all-cause mortality. Anticoagulant prophylaxis conferred an absolute risk reduction of any DVT and proximal DVT of 2.6% and 1.8%, respectively, and was associated with a 0.5% absolute risk increase in major bleeding. CONCLUSIONS Anticoagulant prophylaxis is effective in preventing asymptomatic DVT in at-risk hospitalized medical patients but is associated with an increased bleeding risk. The therapeutic benefits of anticoagulant prophylaxis appear to outweigh the risks of bleeding.