Relationship between aging and dosage of warfarin: the current status of warfarin anticoagulant therapy for Japanese outpatients in a department of cardiovascular medicine

Developing Chinese race-specific warfarin dose prediction algorithms

BACKGROUND

Numerous genotype-guided warfarin dosing algorithms have been developed to individualize warfarin doses, but they can only explain 47-52% of the variability.

AIM

This study aimed to develop new warfarin algorithms suitable to predict the stable warfarin dose for the Chinese population and to compare their prediction performance with those of the most commonly used algorithms.

METHOD

Multiple linear regression analysis with the warfarin optimal dose (WOD), logarithm (log) WOD, 1/WOD, and [Formula: see text], respectively, as the dependent variables were performed to deduce a new warfarin algorithm (NEW-Warfarin). WOD was the stable dose that maintained the international normalized ratio (INR) within the target range (2.0-3.0). Three major genotype-guided warfarin dosing algorithms were selected and compared against NEW-Warfarin predictive performance using the mean absolute error (MAE). Furthermore, patients were divided into five groups according to warfarin indications [atrial fibrillation (AF), pulmonary embolism (PE), cardiac-related disease (CRD), deep vein thrombosis (DVT), and other diseases (OD)]. Multiple linear regression analyses were also performed for each group.

RESULTS

The regression equation with [Formula: see text] as the dependent variable had the highest coefficient of determination (R² = 0.489). The NEW-Warfarin had the best predictive accuracy compared to the three algorithms selected. Group analysis, according to indications, showed that the R² of the five groups were PE (0.902) > DVT (0.608) > CRD (0.569) > OD (0.436) > AF (0.424).

CONCLUSION

Dosing algorithms based on warfarin indications are more suitable for predicting warfarin doses. Our research provides a novel strategy to develop indication-specific warfarin dosing algorithms to improve the efficacy and safety of warfarin prescribing.

Gene Polymorphisms of the Renin-Angiotensin System and Bleeding Complications of Warfarin: Genetic-Based Machine Learning Models

This study aimed to investigate the effects of genetic variants and haplotypes in the renin–angiotensin system (RAS) on the risk of warfarin-induced bleeding complications at therapeutic international normalized ratios (INRs). Four single nucleotide polymorphisms (SNPs) of AGT, two SNPs of REN, three SNPs of ACE, four SNPs of AGTR1, and one SNP of AGTR2, in addition to VKORC1 and CYP2C9 variants, were investigated. We utilized logistic regression and several machine learning methods for bleeding prediction. The study included 142 patients, among whom 21 experienced bleeding complications. We identified a haplotype, H2 (TCG), carrying three single nucleotide polymorphisms (SNPs) of ACE (rs1800764, rs4341, and rs4353), which showed a significant relation with bleeding complications. After adjusting covariates, patients with H2/H2 experienced a 0.12-fold (95% CI 0.02–0.99) higher risk of bleeding complications than the others. In addition, G allele carriers of AGT rs5050 and A allele carriers of AGTR1 rs2640543 had 5.0- (95% CI 1.8–14.1) and 3.2-fold (95% CI 1.1–8.9) increased risk of bleeding complications compared with the TT genotype and GG genotype carriers, respectively. The AUROC values (mean, 95% CI) across 10 random iterations using five-fold cross-validated multivariate logistic regression, elastic net, random forest, support vector machine (SVM)–linear kernel, and SVM–radial kernel models were 0.732 (0.694–0.771), 0.741 (0.612–0.870), 0.723 (0.589–0.857), 0.673 (0.517–0.828), and 0.680 (0.528–0.832), respectively. The highest quartile group (≥75th percentile) of weighted risk score had approximately 12.0 times (95% CI 3.1–46.7) increased risk of bleeding, compared to the 25–75th percentile group, respectively. This study demonstrated that RAS-related polymorphisms, including the H2 haplotype of the ACE gene, could affect bleeding complications during warfarin treatment for patients with mechanical heart valves. Our results could be used to develop individually tailored intervention strategies to prevent warfarin-induced bleeding.

Effect of post-operative anticoagulation management in patients who have undergone On-X mechanical heart valve replacement surgery on post-discharge warfarin therapy

WHAT IS KNOWN AND OBJECTIVE

We evaluated the effect of the proportion of time maintained within the target international normalized ratio (INR) postoperatively in hospitalized patients who underwent On-X mechanical heart valve replacement on warfarin therapy after discharge.

METHODS

Inclusion was patients who were ≥18 years, received warfarin for a minimum of 10 days without any interruptions during hospitalization and followed by the anticoagulation service (ACS) clinic after discharge between June 2006 and June 2016. Patients were excluded if they had incomplete medical records, INR goal changes, known as warfarin resistance, transferred to another facility or expired during the study. The patients were divided into 3 groups according to the proportion of time maintained within therapeutic INR range (TTR) from day 4 to 10 of warfarin initiation (low: <30%, moderate: ≥30% to <70%, and high: ≥70%). The number of days needed to reach target INR for 2 consecutive measurements after discharge and the number of ACS visits was compared among the groups.

RESULTS AND DISCUSSION

Among 539 postoperative patients, 273 were included. The baseline demographics were similar among the 3 groups. The mean time needed to reach target INR for 2 consecutive measurements was 68.6 ± 106.1 days. The low group required time needed to reach target INR for 2 consecutive measurements of 94.0 ± 140.9 days compared with 44.8 ± 57.1 days in the high group (P = .007). Additionally, the low group had more ACS visits than the high group (low, 6.6 ± 5.2 vs high, 4.6 ± 3.9; P = .025). Patient compliance affected the time needed to reach target INR for 2 consecutive measurements (compliant, 42.36 ± 58.5 days vs non-compliant, 132.0 ± 157.1 days, P < .001).

WHAT IS NEW AND CONCLUSION

The study implicated that high postoperative TTR would reduce the time to require post-discharge target INR and the number of ACS visits.

A Simple Formula for Predicting the Maintenance Dose of Warfarin with Reference to the Initial Response to Low Dosing at an Outpatient Clinic

Objective The pharmacodynamic effect of warfarin varies among individuals, and its maintenance dose is widely distributed. Although many formulae for predicting the maintenance dose of warfarin have been developed, most of them are complex and not in practical use. Methods and Materials Among 12,738 new patients visiting the Cardiovascular Institute between 2004 and 2009, we identified 127 patients (66.6±8.8 years, 89 men) with atrial fibrillation for whom warfarin was newly started with an initial dose of 2 mg/day and the international normalized ratio (INR) at 1 year after warfarin was started was within the therapeutic range. The prediction models for the maintenance dose were developed by an exponential equation and a first-order equation. Results The initial response of the INR to the dose of 2 mg/day (initial INR) ranged from 1.00-3.24 (mean 1.43), while the maintenance dose of warfarin ranged from 0.5-14 mg (mean 3.8 mg). The maintenance dose showed an exponential correlation to the initial INR: (predicted maintenance dose) =5.522× (initial INR) ^-1.556 (R²=0.795, p<0.001). Excluding the patients with a poor response to the initial dose (initial INR <1.1, n=32) permitted a simple correlation with a first-order approximation: (predicted maintenance dose) =-2.009× (initial INR) +6.172 (R²=0.706, p<0.001). Conclusion We developed a simple formula for predicting the maintenance dose of warfarin using the initial response of the INR to low-dose warfarin.

Association between VEGFA gene polymorphisms and bleeding complications in patients maintaining therapeutic international normalized ratio

Aim: This study was designed to identify the possible effects of VEGFA polymorphisms on the occurrence of bleeding complications in patients with mechanical heart valves who have achieved therapeutic international normalized ratio (INR). Materials & methods: 13 SNPs of VEGFA were analyzed. Uni- and multi-variate analyses were conducted to identify associations between polymorphisms and bleeding complications. Results & conclusion: Patients with the CC genotype of rs35410204 had an approximately tenfold higher bleeding complication than those with the T allele. For rs866236, patients who had wild-type homozygotes showed an approximately 2.9-fold higher bleeding complication than C allele carriers. This study demonstrated that bleeding complications during warfarin therapy are associated with VEGFA polymorphisms in patients with mechanical heart valves.

Establishment of a Han Chinese-specific pharmacogenetic-guided warfarin dosing algorithm

Warfarin is the most common oral anticoagulant. Because of a narrow therapeutic range, interindividual differences in drug responses, and the risk of bleeding, there are many challenges in using warfarin. We need to predict the warfarin maintenance dose. However, ethnic-specific algorithms may be required, and some Chinese algorithms do not perform adequately. Therefore, we aimed to establish a Han Chinese appropriate algorithm.We recruited a study group consisting of 361 Han Chinese patients receiving warfarin treatment who had heart valve replacements. Genotyping of 38 single nucleotide polymorphisms (SNPs) in 13 candidate genes was carried out using the MassARRAY. In the derivation cohort, a multiple linear regression model was constructed to predict the warfarin dosage. We evaluated the accuracy of our algorithm in the validation cohort and compared it with the other 5 algorithms based on Han Chinese and other races.We established a Han Chinese-specific pharmacogenetic-guided warfarin dosing algorithm. Warfarin maintenance dosage (mg/day) = 1.787 - 0.023 × (Age) + 1.151 × (BSA [m]) + 0.917 × (VKORC1 AG) + 4.619 × (VKORC1 GG) + 0.595 × (CYP4F2 TT) + 0.707 × (CYP2C19 CC). It explained 58.3% of the variance in warfarin doses in Han Chinese patients and was superior to the other 5 algorithms. The ability of the 6 algorithms which estimate the required dose correctly was tested. Our model had a mean absolute error of 0.74 mg/day, the other 5 models have mean absolute error of 0.81 mg/day,1.05 mg/day, 1.24 mg/day, 1.18 mg/day, and 0.85 mg/day, respectively. Our model had a mean percentage error of 26.9%, the other 5 models have the mean percentage error of 27.7%, 27.2%, 52.3%, 45.7%, and 29.3%, respectively.Physicians can not adopt algorithm from other race directly to predict warfarin dose in patients with heart valve replacements, they should establish a new algorithm or adjust another algorithm to fit their patients. The algorithm established in this study has the potential to assist physicians in determining warfarin doses that are close to the appropriate doses.

Pharmacogenetic-guided Warfarin Dosing Algorithm in African-Americans

We aim to develop warfarin dosing algorithm for African-Americans. We explored demographic, clinical, and genetic data from a previously collected cohort of 163 African-American patients with a stable warfarin dose. We explored 2 approaches to develop the algorithm: multiple linear regression and artificial neural network (ANN). The clinical significance of the 2 dosing algorithms was evaluated by calculating the percentage of patients whose predicted dose of warfarin was within 20% of the actual dose. Linear regression model and ANN model predicted the ideal dose in 52% and 48% of the patients, respectively. The mean absolute error using linear regression model was estimated to be 10.8 mg compared with 10.9 mg using ANN. Linear regression and ANN models identified several predictors of warfarin dose including age, weight, CYP2C9 genotype *1/*1, VKORC1 genotype, rs12777823 genotype, rs2108622 genotype, congestive heart failure, and amiodarone use. In conclusion, we developed a warfarin dosing algorithm for African-Americans. The proposed dosing algorithm has the potential to recommend warfarin doses that are close to the appropriate doses. The use of more sophisticated ANN approach did not result in improved predictive performance of the dosing algorithm except for patients of a dose of ≥49 mg/wk.

Determining risk factors of bleeding in patients on warfarin treatment

Background. Warfarin is a commonly used oral anticoagulant agent. The most common adverse effects of warfarin are bleeding complications. Methods. We performed a 1-year retrospective chart review of emergency department patients using warfarin. A total of 65 patients with bleeding disorder (study group) and 63 patients without bleeding (control group) were included, making up a total of 128 subjects. Demographic data, frequency of international normalized ratio (INR) checks, and routine blood results were extracted. Logistic regression analysis was used to determine which factors were most closely associated with bleeding complications. Results. Median age was 62.0 ± 14.4 and 61.9 ± 14.5 for study group and control group, respectively. Educational status and frequency of INR checks were similar in both groups (P = 0.101 and P = 0.483, resp.). INR levels were higher in the study group (5.45 ± 3.98 versus 2.63 ± 1.71, P < 0.001). Creatinine levels were also higher in the study group (1.14 ± 0.57 mg/dL versus 0.94 ± 0.38 mg/dL, P = 0.042). Acetylsalicylic acid use was more frequent in the study group and was associated with a 9-fold increase in bleeding complications (P < 0.001). Conclusions. High INR levels, high creatinine levels, and acetylsalicylic acid use were associated with bleeding complications in ED patients using warfarin.

Trends in Oral Anticoagulation Therapy Among Korean Patients With Atrial Fibrillation: The KORean Atrial Fibrillation Investigation

Background and Objectives

Subjects and Methods

Results

Conclusion

Quality of warfarin control affects the incidence of stroke in elderly patients with atrial fibrillation

OBJECTIVE

Adjusted-dose warfarin therapy can prevent stroke in patients with atrial fibrillation. However, the quality of the warfarin control may be considered to be important for elderly patients. methods: We followed 188 patients (age > or =70 years) with atrial fibrillation (warfarin, 120 patients; non-warfarin, 68 patients) for 2 years. Their warfarin control was assessed by time in therapeutic range (TTR) for an international normalized ratio of prothrombin time of 1.6-2.6, based on the Japanese guidelines of anticoagulation for elderly patients with atrial fibrillation.

RESULTS

Stroke occurred in 23 patients (12.2%). In warfarin-treated patients, receiver-operator characteristic (ROC) curves suggested that patients with TTR >68% had anticoagulation benefit. In the ROC curves for prediction of stroke, the area under the curve of TTR was 0.709 (95% confidence interval, 0.585 to 0.834; p=0.02). The sensitivity and specificity of TTR < or =68% were 91.7% and 54.0%, respectively. Kaplan-Meier curves showed that the event-free ratio of stroke was significantly higher in patients who achieved this cut-off of TTR.

CONCLUSION

The results suggest that the quality of warfarin control is directly associated with the incidence of stroke in elderly patients.