Background: Warfarin is a widely prescribed anticoagulant, and its effect depends on various patient factors including genotypes. Randomized controlled trials (RCTs) comparing genotype-guided dosing (GD) of warfarin with standard dosing have shown mixed efficacy and safety outcomes. We performed a meta-analysis of all published RCTs comparing GD vs standard dosing in adult patients with various indications of warfarin use.
Methods: We searched MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), and relevant references for English language RCTs (inception through March 2014). We performed the meta-analysis using a random effects model.
Results: Ten RCTs with a total of 2,505 patients were included in the meta-analysis. GD compared with standard dosing resulted in a similar % time in therapeutic range (TTR) at ≤ 1 month follow-up (39.7% vs 40.2%; mean difference [MD], -0.52 [95% CI, -3.15 to 2.10]; P = .70) and higher % TTR (59.4% vs 53%; MD, 6.35 [95% CI, 1.76-10.95]; P = .007) at > 1 month follow-up, a trend toward lower risk of major bleeding (risk ratio, 0.46 [95% CI, 0.19-0.1.11]; P = .08) at ≤ 1 month follow-up and lower risks of major bleeding (0.34 [95% CI, 0.16-0.74], P = .006) at > 1-month follow-up, and shorter time to maintenance dose (TMD) (24.6 days vs 34.1 days; MD, -9.54 days [95% CI, -18.10 to -0.98]; P = .03) at follow-up but had no effects on international normalized ratio [INR] > 4.0, nonmajor bleeding, thrombotic outcomes, or overall mortality.
Conclusions: In the first month of genotype-guided warfarin therapy, compared with standard dosing, there were no improvements in % TTR, INR > 4.0, major or minor bleeding, thromboembolism, or all-cause mortality. There was a shorter TMD, and, after 1 month, improved % TTR and major bleeding incidence, making this a cost-effective strategy in patients requiring longer anticoagulation therapy.