Low-molecular-weight heparins and unfractionated heparin in the treatment of patients with acute venous thromboembolism: results of a meta-analysis.
OBJECTIVE
To obtain reliable estimates of the relative efficacy and safety of low-molecular-weight heparins (LMWHs) and unfractionated heparin (UFH) in the treatment of patients with venous thromboembolism.


METHODS
A literature search of randomized trials evaluating LMWH and UFH for the period from 1980 to 1994 was conducted to obtain data for a meta-analysis. Studies were classified as level 1 if they were double-blind or if there was blinded assessment of outcome measures, and level 2 if they did not provide assurance of blinded outcome assessment.


RESULTS
In level 1 studies, the relative risk (RR) of recurrent venous thromboembolism during the first 15 days and over the entire period of anticoagulant therapy was 0.24 (95% confidence intervals [CI] 0.06 to 0.80, P = 0.02) and 0.39 (95% CI 0.30 to 0.80, P = 0.006), respectively, in favor of LMWH treatment. The RR for major bleeding was 0.42 (95% CI 0.2 to 0.9, P = 0.01), in favor of LMWH. In level 2 studies, no significant differences in the rates of recurrent venous thromboembolism or major bleeding were observed. Pooling level 1 and level 2 studies, the RR for overall mortality and mortality in cancer patients was 0.51 (95% CI 0.2 to 0.9, P = 0.01), and 0.33 (95% CI 0.1 to 0.8, P = 0.01), respectively in favor of LMWH.


CONCLUSIONS
LMWH are likely to be more effective than UFH in preventing recurrent venous thromboembolism, to produce less major bleeding, and to be associated with a lower mortality rate, particularly in the subgroup of patients with cancer.
Siragusa
S
S
Department of Internal Medicine, IRCCS Policlinico S. Matteo, Pavia, Italy.
Cosmi
B
B
Piovella
F
F
Hirsh
J
J
Ginsberg
J S
JS
D000208:Acute Disease; D006493:Heparin / Q000627:therapeutic use*; D006495:Heparin, Low-Molecular-Weight / Q000627:therapeutic use*; D006801:Humans; D012008:Recurrence; D012107:Research Design; D016019:Survival Analysis; D013923:Thromboembolism / Q000188:drug therapy* / Q000401:mortality; D013997:Time Factors; D016896:Treatment Outcome
D006495:Heparin, Low-Molecular-Weight; D006493:Heparin