• Emilie P Belley-Cote, Hasib Hanif, Frederick D'Aragon, John W Eikelboom, Jeffrey L Anderson, Mark Borgman, Daniel E Jonas, Stephen E Kimmel, Vangelis G Manolopoulos, Ekaterina Baranova, Anke H Maitland-van der Zee, Munir Pirmohamed, and Richard P Whitlock.
• Richard Whitlock, David Braley Cardiac, Vascular and Stroke Research Institute, Room 1C1-5B, 237 Barton St. E., Hamilton, Ontario L8L 2X2, Canada, Tel.: +1 905 527 4322 ext. 44091, Fax: +1 905 577 8017, E-mail: Richard.Whitlock@phri.ca.
• Thromb Haemostasis. 2015 Oct 1; 114 (4): 768-77.

AbstractVariability in vitamin K antagonist (VKA) dosing is partially explained by genetic polymorphisms. We performed a meta-analysis to determine whether genotype-guided VKA dosing algorithms decrease a composite of death, thromboembolic events and major bleeding (primary outcome) and improve time in therapeutic range (TTR). We searched MEDLINE, EMBASE, CENTRAL, trial registries and conference proceedings for randomised trials comparing genotype-guided and standard (non genotype-guided) VKA dosing algorithms in adults initiating anticoagulation. Data were pooled using a random effects model. Of the 12 included studies (3,217 patients), six reported all components of the primary outcome of mortality, thromboembolic events and major bleeding (2,223 patients, 87 events). Our meta-analysis found no significant difference between groups for the primary outcome (relative risk 0.85, 95% confidence interval [CI] 0.54-1.34; heterogeneity Χ(²)=4.46, p=0.35, I(²)=10%). Based on 10 studies (2,767 patients), TTR was significantly higher in the genotype-guided group (mean difference (MD) 4.31%; 95% CI 0.35, 8.26; heterogeneity Χ(²)=43.31, p<0.001, I(²)=79%). Pre-specified exploratory analyses demonstrated that TTR was significantly higher when genotype-guided dosing was compared with fixed VKA dosing (6 trials, 997 patients: MD 8.41%; 95% CI 3.50,13.31; heterogeneity Χ(²)=15.18, p=0.01, I(²)=67%) but not when compared with clinical algorithm-guided dosing (4 trials, 1,770 patients: MD -0.29%; 95% CI -2.48,1.90; heterogeneity Χ(²)=1.53, p=0.68, I(²)=0%; p for interaction=0.002). In conclusion, genotype-guided compared with standard VKA dosing algorithms were not found to decrease a composite of death, thromboembolism and major bleeding, but did result in improved TTR. An improvement in TTR was observed in comparison with fixed VKA dosing algorithms, but not with clinical algorithms.

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