Warfarin initiation nomograms for venous thromboembolism

There is insufficient evidence on the use of a 10-mg or a 5-mg loading dose for initiation of warfarin for venous thromboembolism.

The quality of evidence is downgraded by study limitations (unclear allocation concealment), by inconsistency (unexplained variability in results), and by imprecise results (wide confidence intervals).

Summary

A Cochrane review included 4 studies with a total of 494 subjects. The proportion of participants who had achieved a therapeutic INR by day 5 was higher with 10-mg warfarin nomogram compared with 5-mg warfarin normogram (table ), although there was substantial heterogeneity (I² = 90%). A sensitivity analysis was performed using the random-effects model, and no difference was observed (RR 1.06, 95% CI 0.52 to 2.16). Each study was analyzed separately because it was not possible to perform a subgroup analysis. One study (n=201) showed significant benefit of a 10-mg warfarin nomogram for the proportion of outpatients with VTE who had achieved a therapeutic INR by day 5 (RR 1.78, 95% CI 1.41 to 2.25; NNTB = 3, 95% CI 2 to 4); another study (n=132) showed significant benefit of a 5-mg warfarin nomogram in outpatients with VTE (RR 0.58, 95% CI 0.36 to 0.93; NNTB = 5, 95% CI 3 to 28); the third study (n=50) showed no difference (RR 1.08, 95% CI 0.65 to 1.80). No difference was observed in recurrent venous thromboembolism, in major bleeding, or in minor bleeding (table ).

Clinical comments

Acute thromboembolism is treated with LMWH together with warfarin dose titration. LMWH treatment is effective and safe, and thus there is no hurry with warfarin titration.

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Ədəbiyyat

1. arcia P, Ruiz W, Loza Munárriz C. Warfarin initiation nomograms for venous thromboembolism. Cochrane Database Syst Rev 2016;(1):CD007699. .