Deep vein thrombosis: LMWH is safer than unfractionated heparin.

Clinical bottom line (level 1a)

  1. Patients with deep vein thrombosis who are given LMWH are less likely to have symptomatic venous thrombosis complications (NNT = 30 at 3-6 months) , or major bleeding (NNT = 53 at 3-6 months) than those given unfractionated heparin.
  2. Patients given LMWH are less likely to die (NNT = 30 at 3-6 months) .
Lensing et al: Archives of Internal Medicine 1995; 155: 601-607
Expires December 2003

The study

Systematic review of randomised trials of
  • Patients: deep vein thrombosis
  • Intervention: low molecular weight heparin compared with unfractionated heparin
  • Outcome: efficacy and safety


    • Articles found in ? no language restrictions using MEDLINE, Current Contents: Clinical Practice, ? no dates given (search terms: heparin or low-molecular-weight heparin, venous thrombo* ) and review of bibliographies, abstracts and inquiring among colleagues knowledgeable in this field

    Selection criteria: as above
    Appraisal criteria: detailed in text
    Articles excluded if:
    • no objective tests to confirm diagnosis
    • heparin dosage not adjusted
    • no independent objective outcome assessment
    • duplicate reports or preliminary reports
    • dose-ranging studies using doses of LMWH higher than currently used


    Ten studies were included, a fixed-effect model was used.
    No significant heterogeneity was noted.

    The evidence

    Outcome Time to outcome CER RR
    (95% CI)    		 NNT
    (95% CI)
    symptomatic venous thromboembolic complications 3-6 months 36/546
    (6.59%)    		 0.47
    (0.27 to 0.82)     		30
    (22 to 88)
    major bleeding 3-6 months 21/656
    (2.77%)    		 0.32
    (0.15 to 0.69)     		53
    (42 to 116)
    mortality 3-6 months 39/546
    (7.14%)    		 0.53
    (0.31 to 0.90)     		30
    (20 to 140)

    Citation

    1. Lensing AW, Prins MH, Davidson BL, et al: Treatment of deep venous thrombosis with low-molecular-weight heparins: A Meta-analysis. Archives of Internal Medicine 1995; 155: 601-607
    Contributor: Clare Wotton and Bob Phillips, December 2000
    Reviewer:

    Clinical Question.
    Patient DVT
    Intervention or Exposure LMWH
    Comparison unfractionated heparin
    Outcome efficacy and safety