Seventeen RCTs were included (n=4,002 patients). Where reported in tables, follow-up duration ranged from three to nine months. All of the studies were open. In 10 studies the outcome assessment was blinded. Unless otherwise stated, no significant heterogeneity was found.
Patients without cancer: (nine studies, n=1,957)
There was no significant difference between LMWH and vitamin K antagonists in recurrent venous thromboembolism for any dose of LMWH (nine studies), full doses of LMWH (five studies, n=1,391) and prophylactic doses of LMWH (significant heterogeneity, I2=73%; four studies, n=566). There was a non-significant trend towards a lower risk of recurrent symptomatic venous thromboembolism from end of treatment to one year in LMWH compared to vitamin K antagonist treatment groups (RR 1.46, 95% CI 0.96 to 2.23; nine studies)
Patients with cancer:
At the end of the assessment period, compared to vitamin K antagonists, there was a significant reduction in recurrent venous thromboembolism associated with full doses of LMWH (RR 0.37, 95% CI 0.19 to 0.74; three studies, n=304) and intermediate doses of LMWH (RR 0.52, 95% CI 0.35 to 0.79; three studies, n=880). There was no significant difference in recurrent venous thromboembolism between vitamin K antagonists and prophylactic doses of LMWH (four studies, n=138).
From the end of treatment to one year, there was no significant difference in risk of recurrence of venous thromboembolism between vitamin K antagonists and full doses of LMWH (9.5% versus 1.6%; three studies, n=252) and between vitamin K antagonists and prophylactic doses of LMWH (7.4% versus 12%; two studies, n=52). The authors stated there was a trend towards a lower risk of recurrent venous thromboembolism with full compared to prophylactic LMWH treatment from the end of treatment to follow-up, but presented no details.
Major bleeding:
All doses of LMWH combined were associated with a significant reduction in the risk of major bleeding compared to vitamin K antagonists (RR 0.58, 95% CI 0.35 to 0.97; 13 studies, n=3,023). There was no significant difference between vitamin K antagonists and full doses of LMWH (five studies, n=1,709) and between vitamin K antagonists and prophylactic doses of LMWH (eight studies, n=1,314).
For patients with cancer, there was no significant difference in rates of major bleeding between vitamin K antagonists and full doses of LMWH (four studies), between vitamin K antagonists and intermediate doses of LMWH (significant heterogeneity I2=64%; three studies) or between vitamin K antagonists and prophylactic doses of LMWH (three studies). Indirect comparison found no significant difference between full and prophylactic doses of LMWH.
Results for recanalisation were reported.