Randomized controlled trial of genotype-guided warfarin anticoagulation in Chinese elderly patients with nonvalvular atrial fibrillation

Pharmacogenetics of warfarin dosing in Chinese adults with nonvalvular atrial fibrillation

BACKGROUND

The guide for the use of genotype-guided warfarin dosing in patients for the treatment of non-valvular atrial fibrillation (AF) is still lacking.

AIM

We aimed to evaluate whether genotype-guided warfarin dosing is superior to conventional clinical dosing for the outcomes of interest in Chinese patients.

METHOD

Our study consisted of 508 newly recruited and 471 existing Chinese AF patients. Among the total 979 patients, 585 patients received their dose of warfarin determined by a genetic and clinical factor (gene group), while the remaining 394 patients whose dosing was determined empirically in control group. We incorporated CYP2C9 and VKORC1 genotypes into the gene group. The international normalized ratio (INR) measurement and standard protocols were used for further dose adjustment in both groups. The primary outcomes were the percentage of time in the therapeutic range (%TTR) and INR during 12-month follow-up. Secondary safety outcome included bleeding and thrombotic events.

RESULTS

Compared with the control group, the average TTR of the gene group was higher [68.4 ± 20.6% vs 48.5 ± 21.6%, P < 0.001]. The average INR monitoring times to reach the therapeutic time in the gene group was lower (P < 0.001). The risk ratios (RR) for cumulative incidence of total bleeding events, minor bleeding events, gastrointestinal bleeding, and intracerebral bleeding events were not significantly different between the two groups (P > 0.05). Comparing to the analysis using existing 471 patients, the analysis using total 979 patients showed that the gene group experienced a lower (RR 0.4 (95% CI 0.2 to 0.8), P = 0.008) incidence of cumulative ischemic stroke.

CONCLUSION

Genotype-guided warfarin administration increases the average TTR, reaches higher TTR levels in the early anticoagulant phase, and significantly reduces the risk of ischemic stroke events.

Ethnic Diversity and Warfarin Pharmacogenomics

Warfarin has remained the most commonly prescribed vitamin K oral anticoagulant worldwide since its approval in 1954. Dosing challenges including having a narrow therapeutic window and a wide interpatient variability in dosing requirements have contributed to making it the most studied drug in terms of genotype-phenotype relationships. However, most of these studies have been conducted in Whites or Asians which means the current pharmacogenomics evidence-base does not reflect ethnic diversity. Due to differences in minor allele frequencies of key genetic variants, studies conducted in Whites/Asians may not be applicable to underrepresented populations such as Blacks, Hispanics/Latinos, American Indians/Alaska Natives and Native Hawaiians/other Pacific Islanders. This may exacerbate health inequalities when Whites/Asians have better anticoagulation profiles due to the existence of validated pharmacogenomic dosing algorithms which fail to perform similarly in the underrepresented populations. To examine the extent to which individual races/ethnicities are represented in the existing body of pharmacogenomic evidence, we review evidence pertaining to published pharmacogenomic dosing algorithms, including clinical utility studies, cost-effectiveness studies and clinical implementation guidelines that have been published in the warfarin field.

Efficacy and safety of genotype-guided warfarin dosing versus non-genotype-guided warfarin dosing strategies: A systematic review and meta-analysis of 27 randomized controlled trials

OBJECTIVE

To evaluate the efficacy and safety of genotype-guided dosing (GD) strategies compared to non-genotype-guided dosing (non-GD) strategies for warfarin.

METHODS

Databases were searched up to July 2021. Meta-analysis was conducted with the Review Manager software (version 5.4) and R (version 4.0.5). Risk ratio (RR), mean difference (MD), and 95% confidence intervals (CIs) were used. Subgroup analyses were conducted based on ethnicity and dosing regimen in non-GD group. Meta-regression was performed to evaluate the relation of covariates. This study is registered with PROSPERO (CRD42021245654).

RESULTS

27 randomized controlled trials with a total of 9906 patients were included. The GD group resulted in a significantly improved time in therapeutic range compared with non-GD group in follow-up duration within 30 days (MD: 5.95, 95%CI: 2.41-9.22, P = 0.001) and beyond 30 days (MD: 4.93, 1.40-8.47, P = 0.006), time to the first therapeutic international normalized ratio (MD: -1.80, -2.69 - -0.92, P < 0.0001), and time to reach stable dose (MD: -5.08, -7.09 - -3.07, P < 0.00001), incidence of major bleeding events (RR: 0.50, 0.33-0.75, P = 0.0008), total bleeding events (RR: 0.83, 0.73-0.95, P = 0.006), and thromboembolism (RR: 0.69, 0.49-0.96, P = 0.03). No differences were found in stable dose achievement, minor bleeding events, over anticoagulation, and all-cause mortality. Four improved efficacy outcomes were observed in GD group compared with fixed dosing group. Only time to the therapeutic INR was shortened in GD group compared with clinical adjusted dosing group. The result showed no difference of safety outcomes between GD group and fixed dosing group whereas a decreased incidence of major bleeding events was observed when comparing to clinical adjusted dosing group.

CONCLUSION

GD strategy was superior to fixed dosing strategy in term of efficacy outcomes and comparable to fixed dosing strategy in safety outcomes. Clinical adjusted regimen could partly substitute the genotype-guided dosing strategy for efficacy in insufficient conditions, but the risk of major bleeding events should be monitored.