Meta-analysis: anticoagulant prophylaxis to prevent symptomatic venous thromboembolism in hospitalized medical patients

Ann Intern Med. 2007 Feb 20;146(4):278-88. doi: 10.7326/0003-4819-146-4-200702200-00007.


Background: Underutilization of anticoagulant prophylaxis may be due to lack of evidence that prophylaxis prevents clinically important outcomes in hospitalized medical patients at risk for venous thromboembolism.

Purpose: To assess the effects of anticoagulant prophylaxis in reducing clinically important outcomes in hospitalized medical patients.

Data sources: MEDLINE, EMBASE, and Cochrane databases were searched to September 2006 without language restrictions.

Study selection: Randomized trials comparing anticoagulant prophylaxis with no treatment in hospitalized medical patients.

Data extraction: Any symptomatic pulmonary embolism (PE), fatal PE, symptomatic deep venous thrombosis, all-cause mortality, and major bleeding. Pooled relative risks and associated 95% CIs were calculated. For treatment effects that were statistically significant, the authors determined the absolute risk reduction and the number needed to treat for benefit (NNT(B)) to prevent an outcome.

Data synthesis: 9 studies (n = 19 958) were included. During anticoagulant prophylaxis, patients had significant reductions in any PE (relative risk, 0.43 [CI, 0.26 to 0.71]; absolute risk reduction, 0.29%; NNT(B), 345) and fatal PE (relative risk, 0.38 [CI, 0.21 to 0.69]; absolute risk reduction, 0.25%; NNT(B), 400), a nonsignificant reduction in symptomatic deep venous thrombosis (relative risk, 0.47 [CI, 0.22 to 1.00]), and a nonsignificant increase in major bleeding (relative risk, 1.32 [CI, 0.73 to 2.37]). Anticoagulant prophylaxis had no effect on all-cause mortality (relative risk, 0.97 [CI, 0.79 to 1.19]).

Limitations: 2 of 9 included studies were not double-blind.

Conclusions: Anticoagulant prophylaxis is effective in preventing symptomatic venous thromboembolism during anticoagulant prophylaxis in at-risk hospitalized medical patients. Additional research is needed to determine the risk for venous thromboembolism in these patients after prophylaxis has been stopped.

Publication types

  • Meta-Analysis
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anticoagulants / adverse effects
  • Anticoagulants / therapeutic use*
  • Bias
  • Hemorrhage / chemically induced
  • Heparin / adverse effects
  • Heparin / therapeutic use
  • Heparin, Low-Molecular-Weight / adverse effects
  • Heparin, Low-Molecular-Weight / therapeutic use
  • Hospital Mortality
  • Hospitalization*
  • Humans
  • Pulmonary Embolism / prevention & control*
  • Sensitivity and Specificity
  • Thromboembolism / prevention & control*
  • Venous Thrombosis / prevention & control*


  • Anticoagulants
  • Heparin, Low-Molecular-Weight
  • Heparin