Genotype-Guided Warfarin Dosing in Patients With Mechanical Valves: A Randomized Controlled Trial

Implementation and Evaluation Strategies for Pharmacogenetic Testing in Hospital Settings: A Scoping Review

BACKGROUND

Pharmacogenetic testing in clinical settings has improved the safety and efficacy of drug treatment. There is a growing number of studies evaluating pharmacogenetic implementation and identifying barriers and facilitators. However, no review has focused on bridging the gap between identifying barriers and facilitators of testing and the clinical strategies adopted in response. This review was conducted to understand the implementation and evaluation strategies of pharmacogenetic testing programs.

METHODS

A PRISMA-compliant scoping review was conducted. The included studies discussed pharmacogenetic testing programs implemented in a hospital setting. Quantitative, qualitative, and mixed design methods were included.

RESULTS

A total of 232 of the 7043 articles that described clinical pharmacogenetic programs were included. The most common specialties that described pharmacogenetic implementation were psychiatry (26%) and oncology (16%), although many studies described institutional programs implemented across multiple specialties (19%). Different specialties reported different clinical outcomes, but all reported similar program performance indicators, such as test uptake and the number of times the test recommendations were followed. There were benefits and drawbacks to delivering test results through research personnel, pharmacists, and electronic alerts, but active engagement of physicians was necessary for the incorporation of pharmacogenetic results into clinical decision making.

CONCLUSIONS

Further research is required on the maintenance and sustainability of pharmacogenetic testing initiatives. These findings provide an overview of the implementation and evaluation strategies of different specialties that can be used to improve pharmacogenetic testing.

Association between gene polymorphisms and initial warfarin therapy in patients after heart valve surgery

BACKGROUND

Warfarin is widely used for the prevention and treatment of thrombotic events. This study aimed to examine the influence of gene polymorphisms on the early stage of warfarin therapy in patients following heart valve surgery.

METHODS

Nine single nucleotide polymorphisms were genotyped using microarray chips, categorizing patients into three groups: normal responders (Group I), sensitive responders (Group II), and highly sensitive responders (Group III). The primary clinical outcomes examined were time in therapeutic range (TTR) and international normalized ratio (INR) variability. To investigate potential influencing factors, a generalized linear regression model was employed.

RESULTS

Among 734 patients, the prevalence of CYP2C9*3-1075A > C, CYP2C19*3-636G > A, and CYP2C19*17-806C > T variants were 11.2%, 9.9%, and 1.9% of patients, respectively. VKORC1-1639G > A or the linked -1173C > T variant was observed in 99.0% of the patients. Generalized linear model analysis revealed an impact of sensitivity grouping on INR variability. Compared to Group I, Group II showed higher TTR values (p = 0.023), while INR variability was poorer in Group II (p < 0.001) and Group III (p < 0.001). Individual gene analysis identified significant associations between CYP2C9*3-1075A > C (p < 0.001), VKORC1-1639G > A or the linked -1173 C > T (p = 0.009) and GGCX-3261G > A (p = 0.019) with INR variability.

CONCLUSION

The genotypes of CYP2C9, VKORC1, and GGCX were found to have a significant impact on INR variability during the initial phase of warfarin therapy. However, no significant association was observed between TTR and gene polymorphisms. These findings suggest that focusing on INR variability is crucial in clinical practice, and preoperative detection of gene polymorphisms should be considered to assist in the initiation of warfarin therapy.

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.

Associated factors and safety of the rapidly achieving first therapeutic target of warfarin in hospitalized patients: a retrospective cohort study

BACKGROUND

Warfarin is a commonly used anticoagulant drug in clinical practice. Rapidly achieving the first therapeutic international normalized ratio (INR) of warfarin may reduce the hospital length of stay. However, little research has been carried out to evaluate the influencing factors and the safety of rapidly achieving the first therapeutic INR target of warfarin.

AIM

To investigate the associated factors and the safety of rapidly achieving the first therapeutic INR target of warfarin.

METHOD

A retrospective cohort study was conducted in inpatients who took warfarin from November 2018 to October 2019. Patients' information was retrieved from medical records.

RESULTS

487 patients were included. The mean achieving first therapeutic target time was 6.0 ± 3.2 days (median, 5.0 days). Age > 65 years, body mass index < 24 kg/m², and initial warfarin dose ≥ 3 mg/d were independent factors associated with the rapidly achieving first INR target of warfarin therapy. The incidence of INR ≥ 4 was higher in patients achieving the first INR target rapidly than those achieving the first INR target slowly, while there were no significant differences in bleeding events between the two groups.

CONCLUSION

Hospitalized patients aged > 65 years, with a body mass index < 24 kg/m², or receiving an initial warfarin dose ≥ 3 mg/d were more likely to achieve the first INR target of warfarin rapidly. Closer INR monitoring and appropriate warfarin dose adjustment are recommended to improve the safety for patients achieving the first INR ≥ 1.8 within 6 days after beginning oral warfarin.

Optimizing the dynamic treatment regime of in-hospital warfarin anticoagulation in patients after surgical valve replacement using reinforcement learning

OBJECTIVE

Warfarin anticoagulation management requires sequential decision-making to adjust dosages based on patients' evolving states continuously. We aimed to leverage reinforcement learning (RL) to optimize the dynamic in-hospital warfarin dosing in patients after surgical valve replacement (SVR).

MATERIALS AND METHODS

10 408 SVR cases with warfarin dosage-response data were retrospectively collected to develop and test an RL algorithm that can continuously recommend daily warfarin doses based on patients' evolving multidimensional states. The RL algorithm was compared with clinicians' actual practice and other machine learning and clinical decision rule-based algorithms. The primary outcome was the ratio of patients without in-hospital INRs >3.0 and the INR at discharge within the target range (1.8-2.5) (excellent responders). The secondary outcomes were the safety responder ratio (no INRs >3.0) and the target responder ratio (the discharge INR within 1.8-2.5).

RESULTS

In the test set (n = 1260), the excellent responder ratio under clinicians' guidance was significantly lower than the RL algorithm: 41.6% versus 80.8% (relative risk [RR], 0.51; 95% confidence interval [CI], 0.48-0.55), also the safety responder ratio: 83.1% versus 99.5% (RR, 0.83; 95% CI, 0.81-0.86), and the target responder ratio: 49.7% versus 81.1% (RR, 0.61; 95% CI, 0.58-0.65). The RL algorithms performed significantly better than all the other algorithms. Compared with clinicians' actual practice, the RL-optimized INR trajectory reached and maintained within the target range significantly faster and longer.

DISCUSSION

RL could offer interactive, practical clinical decision support for sequential decision-making tasks and is potentially adaptable for varied clinical scenarios. Prospective validation is needed.

CONCLUSION

An RL algorithm significantly optimized the post-operation warfarin anticoagulation quality compared with clinicians' actual practice, suggesting its potential for challenging sequential decision-making tasks.

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.

Association between time to therapeutic INR and length of stay following mechanical heart valve surgery

BACKGROUND

Warfarin is the only oral anticoagulant approved for use following mechanical valve surgery (MeVS). Patients may experience prolonged hospital length of stay (LOS) following MeVS awaiting an appropriate warfarin effect. We aimed to determine whether an association exists between time to achieve the first therapeutic international normalized ratio (INR) and LOS following MeVS.

MATERIALS AND METHODS

Retrospective single center cohort study. We included consecutive adult patients undergoing elective MeVS from 2013 to 2018. Landmark analyses and multivariable regression with time-updated INR were used to estimate the association between time to therapeutic INR (TTI) and LOS.

RESULTS

Among 384 patients (median age: 51 years, interquartile range [IQR]: 41-57; 58.3% male), the median TTI was 4 days (IQR: 2-5). Thirty seven percent of patients were discharged with a subtherapeutic INR, many on bridging anticoagulation or with an INR close to target. Those achieving therapeutic INR had an increased rate of hospital discharge (adjusted hazard ratio: 2.17; 95% confidence interval: 1.71-2.76; p < .0001). Attainment of a therapeutic INR anytime between postoperative Days 4 and 13 was significantly associated with a shorter LOS.

CONCLUSIONS

Prolonged time to achieve a therapeutic INR was independently associated with prolonged LOS. Future strategies aimed at improving attainment of therapeutic INR following MeVS may reduce hospital LOS.

A network meta-analysis of CYP2C9, CYP2C9 with VKORC1 and CYP2C9 with VKORC1 and CYP4F2 genotype-based warfarin dosing strategies compared to traditional

WHAT IS KNOWN AND OBJECTIVES

Variations in genotypes were observed in randomized clinical trials (RCTs) that evaluated genotype-based warfarin dosing. We carried out a network meta-analysis to assess whether any clinically significant differences exist between RCTs evaluating CYP2C9 with VKORC1, with CYP2C9 alone and CYP2C9, VKORC1, with CYP4F2 dosing strategies.

METHODS

Electronic records were searched for RCTs comparing genotype-based warfarin with traditional-dosing strategies. Key outcomes included were the time to first therapeutic international normalized ratio (INR); time to stable INR or warfarin dose; percent time in therapeutic range (TTR); and the proportion of patients with supra-therapeutic INR. Weighted mean differences (WMD) and odds ratios (OR) with 95% confidence intervals (95% CI) were the effect estimates.

RESULTS AND DISCUSSION

Twenty-six studies (7898 patients) were included. CYP2C9-based warfarin dosing was associated with a shorter time to first therapeutic INR (WMD: -2.73, 95% CI: -3.41, -2.05) and stable INR/warfarin dose (WMD: -8.1, 95% CI: -12.54, -3.66). CYP2C9 and VKORC1 were observed with a shorter time to first therapeutic INR (WMD: -1.92, 95% CI: -3.23, -0.61) and stable INR/warfarin dose (WMD: -4.6, 95% CI: -6.87, -2.34) along with a longer TTR (%) (WMD: 3.91, 95% CI: 1.18, 6.63). CYP2C9, VKORC1 and CYP4F2 were observed with a reduced proportion of patients with supra-therapeutic INR (OR: 0.68, 95% CI: 0.49, 0.93). Trial sequential analysis confirms the superior benefits of CYP2C9 with VKORC1 genotype.

WHAT IS NEW AND CONCLUSION

The present evidence is supportive of personalizing warfarin dose based only on CYP2C9 and VKORC1 genotypes compared to traditional strategies. More RCTs are needed to delineate any benefit for adding CYP4F2 to provide sufficient power for pooled analysis. No convincing evidence exists supporting the role of CYP2C9 alone.

The Role of Pharmacogenomics in Contemporary Cardiovascular Therapy: A position statement from the European Society of Cardiology Working Group on Cardiovascular Pharmacotherapy

There is a strong and ever-growing body of evidence regarding the use of pharmacogenomics to inform cardiovascular pharmacology. However, there is no common position taken by international cardiovascular societies to unite diverse availability, interpretation and application of such data, nor is there recognition of the challenges of variation in clinical practice between countries within Europe. Aside from the considerable barriers to implementing pharmacogenomic testing and the complexities of clinically actioning results, there are differences in the availability of resources and expertise internationally within Europe. Diverse legal and ethical approaches to genomic testing and clinical therapeutic application also require serious thought. As direct-to-consumer genomic testing becomes more common, it can be anticipated that data may be brought in by patients themselves, which will require critical assessment by the clinical cardiovascular prescriber. In a modern, pluralistic and multi-ethnic Europe, self-identified race/ethnicity may not be concordant with genetically detected ancestry and thus may not accurately convey polymorphism prevalence. Given the broad relevance of pharmacogenomics to areas such as thrombosis and coagulation, interventional cardiology, heart failure, arrhythmias, clinical trials, and policy/regulatory activity within cardiovascular medicine, as well as to genomic and pharmacology subspecialists, this position statement attempts to address these issues at a wide-ranging level.

Genotype-guided warfarin dosing may benefit patients with mechanical aortic valve replacements: randomized controlled study

This prospective, single-blind, randomized study was designed to evaluate the effect of genotype-based warfarin dosing compared with standard warfarin dosing in Korean patients with mechanical cardiac valves. Patients were assigned to either the genotype-based dosing group or the standard dosing group using stratified block randomization. The genotype-based dosing equation was adopted from a previous study which included VKORC1 rs9934438, CYP2C9 rs1057910, CYP4F2 rs2108622, and age. Primary outcomes included the percentage of time in the therapeutic range (pTTR): (i) during the first week following initiation of warfarin therapy, (ii) during hospitalization and (iii) until the first outpatient visit. A total of 91 patients were included in the analysis, 42 treated with genotype-based warfarin dosing and 49 treated with standard warfarin dosing. The genotype frequency differences of the three SNPs included in this study (ie, VKORC1, CYP2C9, CYP4F2), between the genotype-based dosing and standard dosing groups were not different. The genotype-based dosing group trended toward higher pTTR when compared with the standard dosing group, although this difference was not statistically significant. In patients with aortic valve replacement, TTR_Traditional and TTR_Rosendaal were significantly higher in the genotype-based dosing group when compared with the standard dosing group during the first week following treatment initiation [ie, 58.5% vs. 38.1% (p = 0.009) and 64.0% vs. 44.6% (p = 0.012), respectively]. Based on the results, the genotype-guided dosing did not offer a significant clinical advantage, but a possible benefit in patients with aortic valve replacement has been suggested.

Effect of Gene-Based Warfarin Dosing on Anticoagulation Control and Clinical Events in a Real-World Setting

The cytochrome P450 2C9 and vitamin K epoxide reductase complex subunit 1 genotypes are associated with anticoagulation control and the clinical events in warfarin therapy. However, the clinical utility of gene-based warfarin dosing (GBWD) is controversial. We compared the anticoagulation control and clinical events related to warfarin with GBWD to those with clinically fixed dosing (CFD). A retrospective cohort study was conducted in a real-world setting. Of the 915 patients who were reviewed, 844 patients met the study-entry criteria; 413 cases were guided by GBWD using the International Warfarin Pharmacogenetic Consortium algorithm; 431 cases were guided by CFD (2.5 mg/day). The primary outcomes were the time needed to achieve the therapeutic International Normalized Ratio (INR) and the time in the therapeutic range (TTR) during a 3-month timeframe. The time needed to achieve the therapeutic INR (in days) for patients in the GBWD group was shorter than that for patients in the CFD group (10.21 ± 4.68 vs. 14.31 ± 8.26, P < 0.001). The overall TTR (Day 4-90) was significantly different between the GBWD group and CFD group (56.86 ± 10.72 vs. 52.87 ± 13.92, P = 0.007).In subgroup analysis, the TTR was also significantly different between the GBWD group and CFD group during the first month of treatment (Day 4-14: 54.28 ± 21.90 vs. 47.01 ± 26.25, P = 0.012; Day 15-28: 59.60 ± 20.12 vs. 51.71 ± 18.96, P = 0.001). However, no significant difference in the TTR was observed after 29 days of treatment. These data suggest that GBWD provided clinical benefits.

Precision dosing of warfarin: open questions and strategies

Warfarin has a very narrow therapeutic window and obvious interindividual variability in its effects, with many factors contributing to the body's response. Algorithms incorporating multiple genetic, environment and clinical factors have been established to select a precision dose for each patient. A number of randomized controlled trials (RCTs) were conducted to explore whether patients could benefit from these algorithms; however, the results were inconsistent. Some questions remain to be resolved. Recently, new genetic and non-genetic factors have been discovered to contribute to variability in optimal warfarin doses. The results of further RCTs have been unveiled, and guidelines for pharmacogenetically guided warfarin dosing have been updated. Based on these most recent advancements, we summarize some open questions in this field and try to propose possible strategies to resolve them.