Pharmacogenetic testing for clinical applications is steadily increasing. Correct and adequate use of pharmacogenetic tests is important to reduce unnecessary medical costs and adverse patient outcomes. This document contains recommended pharmacogenetic testing guidelines for clinical application, interpretation, and result reporting through a literature review and evidence-based expert opinions for the clinical pharmacogenetic testing covered by public medical insurance in Korea. This document aims to improve the utility of pharmacogenetic testing in routine clinical settings.
Anticoagulants/therapeutic use ; Antidepressive Agents/therapeutic use ; Antimetabolites, Antineoplastic/therapeutic use ; Antitubercular Agents/therapeutic use ; Arylamine N-Acetyltransferase/genetics ; Coronary Artery Disease/drug therapy/genetics ; Cytochrome P-450 CYP2C19/genetics ; Cytochrome P-450 CYP2C9/genetics ; Cytochrome P-450 CYP2D6/genetics ; Depressive Disorder/drug therapy/genetics ; Genotype ; Isoniazid/therapeutic use ; Laboratories, Hospital/standards ; Methyltransferases/genetics ; Pharmacogenomic Testing/*methods/standards ; Platelet Aggregation Inhibitors/therapeutic use ; Pulmonary Embolism/drug therapy/genetics ; Ticlopidine/analogs & derivatives/therapeutic use ; Tuberculosis/drug therapy/genetics ; Vitamin K Epoxide Reductases/genetics ; Warfarin/therapeutic use

PURPOSE: The genes for cytochrome P450 2C9 (CYP2C9) and vitamin K epoxide reductase complex subunit 1 (VKORC1) have been identified as important genetic determinants of warfarin dosing and have been studied. We developed warfarin algorithm for Korean patients with stroke and compared the accuracy of warfarin dose prediction algorithms based on the pharmacogenetics. MATERIALS AND METHODS: A total of 101 patients on stable maintenance dose of warfarin were enrolled. Warfarin dosing algorithm was developed using multiple linear regression analysis. The performance of all the algorithms was characterized with coefficient of determination, determined by linear regression, and the mean of percent deviation was used to predict doses from the actual dose. In addition, we compared the performance of the algorithms using percentage of predicted dose falling within ±20% of clinically observed doses and dividing the patients into a low-dose group (≤3 mg/day), an intermediate-dose group (3-7 mg/day), and high-dose group (≥7 mg/day). RESULTS: A new developed algorithms including the variables of age, body weight, and CYP2C9 and VKORC1 genotype. Our algorithm accounted for 51% of variation in the warfarin stable dose, and performed best in predicting dose within 20% of actual dose and intermediate-dose group. CONCLUSION: Our warfarin dosing algorithm may be useful for Korean patients with stroke. Further studies to elucidate clinical utility of genotype-guided dosing and find the additional genetic association are necessary.
Aged ; *Algorithms ; Anticoagulants/*administration & dosage/therapeutic use ; Cytochrome P-450 CYP2C9/*genetics ; Dose-Response Relationship, Drug ; Female ; Genotype ; Humans ; International Normalized Ratio ; Linear Models ; Male ; Middle Aged ; Multivariate Analysis ; Pharmacogenetics ; Regression Analysis ; Republic of Korea ; Stroke/*drug therapy/ethnology ; Vitamin K Epoxide Reductases/*genetics ; Warfarin/*administration & dosage/therapeutic use

The study aimed to establish a population pharmacokinetic/pharmacodynamic (PPK/PD) model of warfarin. PCR-RFLP technique was used to genotype the CYP2C9 and VKORC1 polymorphisms of 73 patients. RP-HPLC-UV method was used to determine the 190 plasma concentrations of warfarin. Application of NONMEM, the clinical information and 263 international normalized ratio (INR) monitoring data were used to investigate the effect of genetic, physiological, pathological factors, other medication on clearance and anticoagulant response. The final model of warfarin PPK/PD was described as follows: CL = θCL · (WT/60)θWT · θCYP · eηCL (if CYP2C9*1/*1, θCYP = 1; if *1/*3, θCYP = 0.708); EC50 = θEC50 · θVKOR · eηEC50 (if VKORC1- 1639AA, θVKOR = 1; if GA, θVKOR = 2.01; V = θV; K(E0) = θK(E0); Emax = θEmax; E0 = θE0 · eηE0. Among them, the body weight (WT), CYP2C9 and VKORC1 genotype had conspicuous effect on warfarin PK/PD parameters. The goodness diagnosis, Bootstrap, NPDE verification showed that the final model was stable, effective and predictable. It may provide a reference for opitimizing the dose regimen of warfarin.
Anticoagulants ; pharmacology ; Body Weight ; Cytochrome P-450 CYP2C9 ; genetics ; Genotype ; Humans ; International Normalized Ratio ; Nonlinear Dynamics ; Polymorphism, Genetic ; Vitamin K Epoxide Reductases ; genetics ; Warfarin ; pharmacokinetics

OBJECTIVE To assess the influence of genetic polymorphisms and non-genetic factors on warfarin maintenance dose variations in order to provide guidance for personalized use of warfarin. METHODS Two hundred patients from outpatient and inpatient with stable international normalized ratio(INR) were recruited. Clinical data and blood samples were collected. Genotypes of 4 genes involved in warfarin metabolic pathways were determined with Sanger sequencing. Based on statistical analysis of warfarin maintenance dosage, a mathematical model was established. RESULTS Among non-genetic factors, the age and height have significant influence in warfarin dosage. The dosage is negatively correlated with age but positively correlated with height. The difference in dosage for between the 20-year-old group and 60-year-old group has reached 1.81 mg/day, and that for between the 140 cm in height and 180 cm in height groups has reached 1.06 mg/day. VKORC1 -1639G/A, CYP2C9 430C/T, CYP2C9 1075A/C and CYP4F2 V433M polymorphisms have significant influence on stable warfarin dosage. The dosage for patients with wild type and mutant genotypes has varied from 0.35 mg/day to 0.84 mg/day. CONCLUSION Non-genetic factors and genetic polymorphisms play important roles in personalized variations of warfarin maintenance dose. The establishment of mathematical models considering multiple factors is helpful in evaluating the safety and effectiveness of warfarin dosage.
Adult ; Aged ; Anticoagulants ; administration & dosage ; Cytochrome P-450 CYP2C9 ; genetics ; Cytochrome P-450 Enzyme System ; genetics ; Cytochrome P450 Family 4 ; Female ; Humans ; Male ; Middle Aged ; Polymorphism, Genetic ; Vitamin K Epoxide Reductases ; genetics ; Warfarin ; administration & dosage

A 73-yr-old Korean man with permanent atrial fibrillation visited outpatient clinic with severely increased International Normalized Ratio (INR) values after taking a usual starting dosage of warfarin to prevent thromboembolism. We found out later from his blood tests that he had hyperthyroidism at the time of treatment initiation. His genetic analysis showed CYP2C9*1/*3 and VKORC1+1173TT genotypes. We suspect that both hyperthyroidism and genetic variant would have contributed to his extremely increased INR at the beginning of warfarin therapy. From this case, we learned that pharmacogenetic and thyroid function test might be useful when deciding the starting dosage of warfarin in patients with atrial fibrillation.
Aged ; Anticoagulants/blood/metabolism/therapeutic use ; Aspirin/therapeutic use ; Atrial Fibrillation/*diagnosis ; Chromatography, High Pressure Liquid ; Cytochrome P-450 CYP2C9/*genetics ; Genotype ; Humans ; Male ; Polymorphism, Single Nucleotide ; Tandem Mass Spectrometry ; Thromboembolism/prevention & control ; Thyrotoxicosis/*diagnosis ; Vitamin K Epoxide Reductases/genetics ; Warfarin/*blood/metabolism/therapeutic use

<p>OBJECTIVETo evaluate the effect of VKORC1, CYP2C9, GGCX, PROC, EPHX1 and CYP4F2 gene polymorphisms on Warfarin maintenance dose variation in Chinese Han Population.p><p>METHODSFour hundred eighty-eight patients with prosthetic heart valves, atrial fibrillation or pulmonary thromboembolism and achieved stable Warfarin dose were enrolled. TaqMan probe or direct sequencing were used to genotype Y9VKORC1, CYP2C9, GGCX, EPHX1 and CYP4F2 gene polymorphisms. Demographic characteristics, stable therapeutic dose of Warfarin and concomitant medications were collected for all patients. The effect of VKORC1, CYP2C9, GGCX, PROC, EPHX1 and CYP4F2 gene polymorphisms, demographic characteristics and concomitant medications on Warfarin daily maintenance dose were analyzed with statistical method.p><p>RESULTSVKORC1 and CYP2C9 gene polymorphisms could explain more than 50% Warfarin maintenance dose variation in recruited patients, while CYP4F2 gene polymorphisms could only explain 1%. GGCX, PROC and EPHX1 gene polymorphisms had no impact no Warfarin maintenance dose. VKORC1 and CYP2C9 gene polymorphisms have a greater impact on Warfarin maintenance dose compared with demographic characteristics and concomitant medications.p><p>CONCLUSIONVKORC1 and CYP2C9 gene polymorphisms have a significant impact on Warfarin maintenance dose in Chinese Han population.p>
Adult ; Aged ; Aryl Hydrocarbon Hydroxylases ; genetics ; Asian Continental Ancestry Group ; ethnology ; genetics ; Atrial Fibrillation ; drug therapy ; ethnology ; genetics ; Cytochrome P-450 CYP2C9 ; Cytochrome P-450 Enzyme System ; genetics ; Cytochrome P450 Family 4 ; Dose-Response Relationship, Drug ; Epoxide Hydrolases ; genetics ; Female ; Humans ; Male ; Middle Aged ; Polymorphism, Single Nucleotide ; Protein C ; genetics ; Pulmonary Embolism ; drug therapy ; ethnology ; genetics ; Treatment Outcome ; Vitamin K Epoxide Reductases ; genetics ; Warfarin ; administration & dosage ; Young Adult

<p>OBJECTIVETo investigate the distribution of Warfarin related genes and the relationship between genotype, gender, weight, age and the administrative dose of Warfarin in Shanghai area.p><p>METHODSThe clinical data (including sex, age and administrative dose of Warfarin) of 214 patients with stable warfarin dose and the international normalized ratio (INR) between 1.5-3.0 were collected. Polymerase chain reaction-high resolution melting (PCR-HRM) technique was used to detect the single nucleotide polymorphisms (SNPs) of CYP2C9*2 rs1799853, CYP2C9*3 rs1057910, CYP4F2 rs2108622 and VKORC1 rs9934438. The associations of genotype data with clinical material, including gender, age, weight and warfarin dosage were analyzed.p><p>RESULTSAmong 214 patients, 99.53% (213 cases) patients with CC (wild type) of CYP2C9*2 rs1799853 and only 1 case with CT (heterozygous mutation) ; 92.52% (198 cases) with AA (wild type), 7.48% (16 cases) with CA (heterozygous mutation) of CYP2C9*3rs1057910; about 57.94% (124 cases) with CC(wild type) of CYP4F2 rs2108622, the CT and TT (heterozygous and homozygotic mutation) accounted for 42.06% (90 cases). In SNP VKORC1 rs9934438, 82.71% (177cases) were TT (wild type), 17.29% (37 cases) CT (heterozygous mutation). There are no significant difference (P=0.0872) in patients with maintenance dose in CYP2C9*3 between AA and CA gene mutations[(2.816±1.055) mg/d vs (2.352±0.805)mg/d], and no significant difference (P=0.5954) of that in CYP4F2 between CC and CT+TT gene mutations [(2.736±1.062) mg/d vs (2.813±1.034) mg/d]; but the significant differences (P=0.0001) does exist in patients with maintenance dose in VKORC1 between TT and CT variants [(2.597±0.866) mg/d vs (3.660±1.350) mg/d]. The warfarin maintain dosage was negatively correlated with the average age (r=-0.9669) and positively correlated with the body weight (r=0.9022).p><p>CONCLUSIONIt is of great significance to detect the VKORC1 variants for warfarin dosage adjustment in Shanghai population. However, the detection of CYP2C9*2 and CYP4F2 polymorphisms had no significant associations for warfarin dosage adjustment.p>
Adult ; Aged ; Aged, 80 and over ; Anticoagulants ; administration & dosage ; Body Weight ; China ; epidemiology ; Cytochrome P-450 CYP2C9 ; genetics ; Cytochrome P-450 Enzyme System ; genetics ; Cytochrome P450 Family 4 ; Dose-Response Relationship, Drug ; Female ; Genotype ; Heterozygote ; Humans ; International Normalized Ratio ; Male ; Middle Aged ; Sex Distribution ; Vitamin K Epoxide Reductases ; genetics ; Warfarin ; administration & dosage ; Young Adult

<p>BACKGROUNDPatients with the genotypes of both CYP2C9*3/*3 and VKORC1-1639 A/A are expected to require the lowest dose of warfarin, and to have a greatly increased risk of bleeding. The experience for the dosing of warfarin in such extremely rare cases has been seldom reported.p><p>METHODSDemographic and clinical data from two cases with stable low dose of warfarin in China were studied by resequencing the corresponding gene segments in their whole blood DNA. The potential clinical value of the pharmacogenetic algorithm for them was evaluated by calculating the stable dose of warfarin in pharmacogenetic algorithm developed by International Warfarin Pharmacogenetics Consortium.p><p>RESULTSBoth cases (68-year-old female and 50-year-old male) were diagnosed as chronic nonvalvular atrial fibrillation needing warfarin treatment, with target international normalized ratio (INR) 2 to 3. Case 1 had stable warfarin dose of 0.625 mg/d and case 2 1.25 mg/d. They needed more than 1 month to stabilize their anticoagulation. Exceeding INR values were recorded for them when the dose of warfarin was no more than 2 mg/d. Hemorrhagic complication appeared in case 1 when the dose was titrated from 2.5 to 1.25 mg/d. No concomitant medicine to increase or decrease the INR value was recorded for them. Genotyping CYP2C9 and VKORC1 showed both patients were the carriers of the homozygous alleles -CYP2C9*3/*3 and VKORC1-1639 A/A. Their stable doses of warfarin calculated by the pharmacogenetic dose algorithm (0.672 mg/d for case 1 and 1.16 mg/d for case 2) were comparable with their actual stable therapeutic doses.p><p>CONCLUSIONSTwo Chinese with the rare genotypes of both CYP2C9*3/*3 and VKORC1-1639 A/A were found to require the extremely low dose of warfarin. The pharmacogenetic algorithm incorporating the variances of VKORC1 and CYP2C9 genotypes, as well as the non-genetic factors could predict their stable dose of warfarin with high accuracy.p>
Aged ; Anticoagulants ; adverse effects ; Aryl Hydrocarbon Hydroxylases ; genetics ; Cytochrome P-450 CYP2C9 ; Female ; Genotype ; Hemorrhage ; chemically induced ; Humans ; Male ; Middle Aged ; Mixed Function Oxygenases ; genetics ; Pharmacogenetics ; Vitamin K Epoxide Reductases ; Warfarin ; adverse effects

<p>OBJECTIVETo investigate the effect of genetic polymorphisms in VKORC1, CYP2C9, GGCX, EPHX1, APOE genes on inter-individual variation in warfarin maintenance dose.p><p>METHODSTwo hundred and forty-nine patients with stable warfarin dose were enrolled in this study, and the clinical data and blood samples of the patients were collected. Genotypes for the 5 genes were determined by using PCR and denaturing high performance liquid chromatography (DHPLC) assay. The warfarin maintenance doses were compared among patients with different genotypes of the 5 genes, and a warfarin stable dosing algorithm was derived based on genetic and non-genetic factors.p><p>RESULTSOf the 5 genes, VKORC1, CYP2C9 and GGCX were associated with warfarin stable dose. The multiple linear regression analysis indicated that VKORC1, CYP2C9 and GGCX genes, age and weight, had significant influence on inter-individual variation in warfarin stable dose, which contributed 30.2%, 22.8%, 1.5%, 4.7% and 6.7% respectively. The warfarin stable dosing algorithm acquired from the optimal regression model could explain 57.8% variation in warfarin dose.p><p>CONCLUSIONThis study suggested that genetic factors are the major determinants of the warfarin maintenance dose, and warfarin stable dosing algorithm may be useful for helping clinicians to prescribe warfarin with greater safety and efficiency.p>
Adolescent ; Adult ; Aged ; Aged, 80 and over ; Alleles ; Anticoagulants ; administration & dosage ; Apolipoproteins E ; genetics ; Aryl Hydrocarbon Hydroxylases ; genetics ; Carbon-Carbon Ligases ; genetics ; Cytochrome P-450 CYP2C9 ; Epoxide Hydrolases ; genetics ; Female ; Gene Frequency ; Genotype ; Humans ; Male ; Middle Aged ; Mixed Function Oxygenases ; genetics ; Pharmacogenetics ; Polymorphism, Single Nucleotide ; Precision Medicine ; Vitamin K Epoxide Reductases ; Warfarin ; administration & dosage ; Young Adult

<p>OBJECTIVETo investigate the association of the polymorphisms of cytochrome P450 2C9 (CYP2C9) exon 4 608T/G, 561A/C, 537A/C and 527A/C, and -65G/C with warfarin sensitivity.p><p>METHODSA total of 102 patients under warfarin anticoagulant therapy were selected. During follow-up, warfarin dosage and associated Prothrombin Time-International Normalized Ratio (P-INR) values were recorded. Simultaneous monitoring of incidence of bleeding and thrombosis adverse effect was recommended. Genetic polymorphisms of the above mentioned loci were identified by polymerase chain reaction and DNA sequencing.p><p>RESULTSThe average age of the 102 patients was (62.1+/-10.5) years. The body mass index (BMI) was (24.7+/-3.8) kg/m2. Mean daily warfarin requirement was from 1.250 to 5.077 mg/day when therapeutic PT-INR (1.5-2.5) was maintained. DNA sequencing showed no polymorphisms of 608T/G, 561A/C, 537A/C, 527A/C in CYP2C9 exon 4. Warfarin daily dosage in CYP2C9 exon 4 -65C carriers was 3.106+/-0.619 mg/d, while it was (2.555+/-0.708) mg/d in individuals with wild-type -65G (P=0.020). Receiver operating characteristic (ROC) analysis showed that warfarin daily dosage of more than 2.5 mg/d can be used to predict the CYP2C9 exon 4 -65GC genotype (AUC: 0.770, P=0.005, 95%CI:0.626-0.915). Logistic regression indicated that BMI was an independent factor of bleeding during anti-coagulation therapy (OR=0.794, 95%CI: 0.651-0.970, P=0.024).p><p>CONCLUSIONThe Chinese population are, generally, warfarin-sensitive. Exon 4 of the CYP2C9 gene is highly conserved in this population. The warfarin maintenance dosage in CYP2C9 exon 4 -65CG carriers was significantly higher than those with wild-type -65GG. The clinical significance needs further investigation with more large-scale, multi-center trials.p>
Adult ; Alleles ; Anticoagulants ; pharmacology ; therapeutic use ; Aryl Hydrocarbon Hydroxylases ; genetics ; Cytochrome P-450 CYP2C9 ; Exons ; genetics ; Female ; Genetic Predisposition to Disease ; Genotype ; Humans ; Male ; Middle Aged ; Point Mutation ; Polymorphism, Genetic ; Thrombosis ; drug therapy ; Warfarin ; pharmacology ; therapeutic use