Evaluation of genetic factors for warfarin dose prediction

OBJECTIVES: Warfarin is a commonly prescribed anticoagulant drug used to prevent thromboses that may arise as a consequence of orthopedic and vascular surgery or underlying cardiovascular disease. Warfarin is associated with a notoriously narrow therapeutic window where small variations in dosing may result in hemorrhagic or thrombotic complications. To ultimately improve dosing of warfarin, we evaluated models for stable maintenance dose that incorporated both clinical and genetic factors. METHOD: A model was constructed by evaluating the contribution to dosing variability of the following clinical factors: age, gender, body surface area, and presence or absence of prosthetic heart valves or diabetes. The model was then sequentially expanded by incorporating polymorphisms of cytochrome P450 (CYP) 2C9; vitamin K 2,3 epoxide reductase complex, subunit 1 (VKORC1); gamma carboxylase; factor VII; and apolipoprotein (Apo) E genes. RESULTS: Of genetic factors evaluated in the model, CYP2C9 and VKORC1 each contributed substantially to dose variability, and together with clinical factors explained 56% of the individual variability in stable warfarin dose. In contrast, gamma carboxylase, factor VII and Apo E polymorphisms contributed little to dose variability. CONCLUSION: The importance of CYP2C9 and VKORC1 to patient-specific dose of warfarin has been confirmed, while polymorphisms of gamma carboxylase, factor VII and Apo E genes did not substantially contribute to predictive models for stable warfarin dose.     

Genetic factors contribute to bleeding after cardiac surgery

BACKGROUND: Postoperative bleeding remains a common, serious problem for cardiac surgery patients, with striking inter-patient variability poorly explained by clinical, procedural, and biological markers. OBJECTIVE: We tested the hypothesis that genetic polymorphisms of coagulation proteins and platelet glycoproteins are associated with bleeding after cardiac surgery. PATIENTS/METHODS: Seven hundred and eighty patients undergoing aortocoronary surgery with cardiopulmonary bypass were studied. Clinical covariates previously associated with bleeding were recorded and DNA isolated from preoperative blood. Matrix Assisted Laser Desorption/Ionization, Time-Of-Flight (MALDI-TOF) mass spectroscopy or polymerase chain reaction were used for genotype analysis. Multivariable linear regression modeling, including all genetic main effects and two-way gene-gene interactions, related clinical and genetic predictors to bleeding from the thorax and mediastinum. RESULTS: Nineteen candidate polymorphisms were assessed; seven [GPIaIIa-52C>T and 807C>T, GPIb alpha 524C>T, tissue factor-603A>G, prothrombin 20210G>A, tissue factor pathway inhibitor-399C>T, and angiotensin converting enzyme (ACE) deletion/insertion] demonstrate significant association with bleeding (P < 0.01). Adding genetic to clinical predictors results improves the model, doubling overall ability to predict bleeding (P < 0.01). CONCLUSIONS: We identified seven genetic polymorphisms associated with bleeding after cardiac surgery. Genetic factors appear primarily independent of, and explain at least as much variation in bleeding as clinical covariates; combining genetic and clinical factors double our ability to predict bleeding after cardiac surgery. Accounting for genotype may be necessary when stratifying risk of bleeding after cardiac surgery.     

Use of pharmacogenetic and clinical factors to predict the therapeutic dose of warfarin

Initiation of warfarin therapy using trial-and-error dosing is problematic. Our goal was to develop and validate a pharmacogenetic algorithm. In the derivation cohort of 1,015 participants, the independent predictors of therapeutic dose were: VKORC1 polymorphism -1639/3673 G>A (-28% per allele), body surface area (BSA) (+11% per 0.25 m(2)), CYP2C9(*)3 (-33% per allele), CYP2C9(*)2 (-19% per allele), age (-7% per decade), target international normalized ratio (INR) (+11% per 0.5 unit increase), amiodarone use (-22%), smoker status (+10%), race (-9%), and current thrombosis (+7%). This pharmacogenetic equation explained 53-54% of the variability in the warfarin dose in the derivation and validation (N= 292) cohorts. For comparison, a clinical equation explained only 17-22% of the dose variability (P < 0.001). In the validation cohort, we prospectively used the pharmacogenetic-dosing algorithm in patients initiating warfarin therapy, two of whom had a major hemorrhage. To facilitate use of these pharmacogenetic and clinical algorithms, we developed a nonprofit website, http://www.WarfarinDosing.org.     

Factors determining the maintenance dose of warfarin in Chinese patients

Chinese patients are reportedly more sensitive than Caucasians to the anticoagulant effect of warfarin. We examined warfarin dose requirements and their determinants in 151 Chinese out-patients on stable maintenance dose of warfarin with international normalized ratio of 2 to 2.5. Mean daily warfarin requirement was 3.3 +/- 1.4 mg, much lower than reported doses in Caucasian patients. The most important determinant was age (r = -0.43, p < 0.001), with progressively lower warfarin requirement with increasing age (p = 0.0001). There was a weaker association with body weight (r = 0.20, p = 0.01). Patients with chronic rheumatic heart disease tended to require a smaller dose than those with heart valve replacements (2.94 +/- 1.24 vs. 3.69 +/- 1.42 mg, p < 0.01). We confirm that Chinese patients require a smaller dose of warfarin for the same degree of anticoagulation. Age is the most important factor affecting dose requirement, although body weight and underlying disease also play a role.      

Dosing algorithms to predict warfarin maintenance dose in Caucasians and African Americans

The objective of this study was to determine whether warfarin dosing algorithms developed for Caucasians and African Americans on the basis of clinical, environmental, and genetic factors will perform better than an empirical starting dose of 5 mg/day. From April 2002 through December 2005, 259 subjects (Caucasians and African Americans) who started using warfarin were prospectively followed until they reached maintenance dose. The Caucasian algorithm included 11 variables (R(2) = 0.43). This model (which predicted 51% of the doses to within 1 mg of the observed dose) performed better than 5 mg/day (which predicted 29% of the doses to within 5 +/- 1 mg). The African-American algorithm included 10 variables (R(2) = 0.28). This model predicted 37% of the doses to within 1 mg of the observed dose, representing a small improvement compared with 5 mg/day (which predicted 34% of the doses to within 1 mg of 5 mg/day). These results were similar to the results we obtained from testing other published algorithms. The dosing algorithms explained <45% of the observed variability in Caucasians, and the algorithms performed only marginally better for African Americans when compared with giving 5 mg empirically.     

Predicting warfarin maintenance dose in patients with venous thromboembolism based on the response to a standardized warfarin initiation nomogram

Summary. Background: Polymorphisms in the VKORC1 and CYP2C9 genes influence warfarin requirements. It has been suggested that dosing algorithms incorporating them might outperform usual care. Standardized warfarin initiation nomograms are safe and effective and patients’ responses to them could be used to predict warfarin requirements without the need for genetic testing. Objectives: To develop a model to predict warfarin dose requirements based on the response to a standard nomogram without using genetic testing. Patients/methods: We included 363 outpatients with acute venous thromboembolism who were started on treatment using a standardized warfarin nomogram and achieved a stable maintenance warfarin dose defined as a dose prescribed twice consecutively after two consecutive INR measurements between 2.0 and 3.0. Linear regression was used to derive equations predicting the maintenance dose and models were validated using non‐parametric bootstrapping and tested in an independent cohort. Results: Three models were constructed for patients completing the nomogram until day 3 (warfarin dose (mg week^?1) = Exp [2.737 + 1.896(INR₃^?1)?0.008(Age)]; R²_adj = 0.462), day 5 (warfarin dose (mg week^?1) = Exp[2.261 + 2.412(INR₃^?1) ?0.285(ΔINR_5?3)]; R²_adj = 0.603) and day 8 (warfarin dose (mg week^?1) = Exp[1.574 + 1.788(INR₈^?1) + 0.024(cumulated warfarin dose until nomogram day 7)]; R²_adj = 0.643), where Exp is the exponential function; INR₃ and INR₈ are the INR on days 3 or 8 of the nomogram, and ΔINR_5?3 is the difference in the INR on days 5 and 3. All models were internally and externally validated and were accurate to within 25% of the actual dose in >60% of patients. Conclusion: Maintenance warfarin dose can be accurately predicted using individual response to a standard warfarin initiation nomogram without the need for costly genetic testing.     

Four-factor prothrombin complex concentrate dose response relationship with INR for warfarin reversal

IntroductionFor reversal of warfarin-induced coagulopathy, FDA labeling of four-factor prothrombin complex concentrate (4F-PCC) endorses a dosing strategy based on body weight and baseline INR. Recent literature suggests lower, fixed doses of 4F-PCC may be equally efficacious. The present evaluation aims to characterize the relationship between 4F-PCC dose and degree of reduction in INR.MethodsThis is a retrospective, single-center review of 4F-PCC administrations for warfarin reversal between May 2014 and August 2017. The primary endpoint evaluates the relationship between doses of 4F-PCC and INR measurement after reversal, represented as a linear regression. Exploratory endpoints characterize the relationships of both body weight and baseline INR, the components determining initial 4F-PCC dose, with INR after reversal. Additionally, for records presenting with an INR of 2–3.9, mean INR after reversal was characterized as a function of two 4F-PCC dose cohorts (< 30 and ≥30 IU fIX/kg).ResultsA significant linear relationship between 4F-PCC dose and INR after reversal (INR after 4F-PCC = 1.3651–0.00004(4F-PCC Dose), p = 0.0071, R² = 0.0630) was observed. Body weight and baseline INR were not correlated with INR after reversal. The subgroup analysis of records with presenting INR of 2–3.9 demonstrated no difference in mean INR after reversal with 4F-PCC for those receiving <30 IU fIX/kg and those receiving ≥30 IU fIX/kg.ConclusionThis evaluation found no clinically relevant relationship with 4F-PCC doses and degree of INR reversal. Further prospective study is required to determine optimal dosing schemes of 4F-PCC for warfarin reversal.     

汉族人群血管紧张素转换酶基因插入／缺失（I／D）的遗传多态性

背景：血管紧张素转换酶是肾素-血管紧张素-醛固酮系统的重要组成部分，血管紧张素转换酶基因第16内含子内存在一个287bp的 Alu序列的插入／缺失（I／D）多态性，与心血管疾病、IgA肾病等疾病的发生具有一定的相关性。 目的：分析汉族人群血管紧张素转换酶基因插入／缺失（I／D）多态性的分布，并与已知的其他种族人群进行比较。 设计：以健康汉族人为观察对象的观察性实验。 单位：江苏省临床免疫学重点实验室，苏州大学附属第一医院检验科，江苏大学医学技术学院检验系。 对象：受检者为2005-12／2006-01苏州大学附属第一医院门诊健康体检者241名，男152名，女89名，平均年龄（27&;#177;8）岁，均为无血缘关系的苏州地区汉族人，经临床及实验室检查确认排除肝、肾、内分泌、心脑血管疾病. 方法：应用聚合酶链反应检测了241名汉族健康体检者血管紧张素转换酶基因I／D多态性等位基因的基因型，并采用荧光标记末端终止法对基因型为D／D、I／I的PCR纯化产物进行DNA测序确认。 主要观察指标：血管紧张素转换酶基因I／D基因型，等位基因频率以及与其他种族人群的比较。 结果：241名受检者全部进入结果分析。①血管紧张素转换酶的基因型表现为缺失纯合子（DD）、插入纯合子（Ⅱ）以及缺失和插入杂合子（DI），等位基因D较等位基因I缺失一段287bp的核苷酸，即Alu序列。（2）Ⅱ，ID,DD基因型频率分别为46．1％，41．5％，12．4％；等位基因I，D频率分别为66．8％，33．2％。（3）日本人与汉族人群血管紧张素转换酶基因型分布相似，均以Ⅱ型最常见，DD型最少；欧美人群以ID居多，Ⅱ型较少。汉族人群与日本人及欧美人群血管紧张素转换酶基因型频率的分布具有种族差异性。与其他各民族人群比较，汉族人群等位基因Ⅰ显著高于上述各民族（X^2=105．55，P〈0．01），等位基因D明显较低（X^2=87．54，P〈0．01）. 结论：血管紧张素转换酶基因多态性具有种族差异性。了解不同种族人群间血管紧张素转换酶基因多态性的遗传特点，是研究血管紧张素转换酶基因I／D多态性与疾病相关性的基础和前提。     

A proposal for an individualized pharmacogenetics-based warfarin initiation dose regimen for patients commencing anticoagulation therapy

A significant proportion of the interindividual variability in warfarin dose requirements can be explained on the basis of CYP2C9 and VKORC1 genotypes. We report the development of a novel pharmacogenetics-based 3-day warfarin initiation dose (ID) algorithm based on the International Warfarin Pharmacogenetics Consortium (IWPC) maintenance dose algorithm and the CYP2C9 genotype-based variance in warfarin half-life. The predictive value of the pharmacogenetics-based ID was assessed in a large cohort of 671 newly diagnosed patients with thromboembolic disorders who were about to commence anticoagulation therapy in accordance with standard induction regimens. In patients with mean international normalized ratio (INR)days 4-7>4.0 (n=63) after warfarin initiation, the pharmacogenetics-based ID algorithm predicted a markedly lower dose requirement (median reduction=4.2 mg), whereas in those with mean INRdays 4-7<2.0 (n=145), the predicted dose requirement was very similar to that in the standard regimen. The use of a pharmacogenetics-based ID may avoid overshooting of INR in warfarin-sensitive patients without unduly affecting the time taken to reach target range in the majority of patients.     

汉族人群血管紧张素转换酶基因插入/缺失(I/D)的遗传多态性

背景:血管紧张素转换酶是肾素-血管紧张素-醛固酮系统的重要组成部分,血管紧张素转换酶基因第16内含子内存在一个287bp的Alu序列的插入/缺失(I/D)多态性,与心血管疾病、IgA肾病等疾病的发生具有一定的相关性。目的:分析汉族人群血管紧张素转换酶基因插入/缺失(I/D)多态性的分布,并与已知的其他种族人群进行比较。设计:以健康汉族人为观察对象的观察性实验。单位:江苏省临床免疫学重点实验室,苏州大学附属第一医院检验科,江苏大学医学技术学院检验系。对象:受检者为2005-12/2006-01苏州大学附属第一医院门诊健康体检者241名,男152名,女89名,平均年龄(27±8)岁,均为无血缘关系的苏州地区汉族人,经临床及实验室检查确认排除肝、肾、内分泌、心脑血管疾病。方法:应用聚合酶链反应检测了241名汉族健康体检者血管紧张素转换酶基因I/D多态性等位基因的基因型,并采用荧光标记末端终止法对基因型为D/D、I/I的PCR纯化产物进行DNA测序确认。主要观察指标:血管紧张素转换酶基因I/D基因型,等位基因频率以及与其他种族人群的比较。结果:241名受检者全部进入结果分析。①血管紧张素转换酶的基因型表现为缺失纯合子(DD)、插入纯合子(II)以及缺失和插入杂合子(DI),等位基因D较等位基因Ⅰ缺失一段287bp的核苷酸,即Alu序列。②II,ID,DD基因型频率分别为46.1%,41.5%,12.4%;等位基因I,D频率分别为66.8%,33.2%。③日本人与汉族人群血管紧张素转换酶基因型分布相似,均以II型最常见,DD型最少;欧美人群以ID居多,II型较少。汉族人群与日本人及欧美人群血管紧张素转换酶基因型频率的分布具有种族差异性。与其他各民族人群比较,汉族人群等位基因I显著高于上述各民族(χ2=105.55,P<0.01),等位基因D明显较低(χ2=87.54,P<0.01)。结论:血管紧张素转换酶基因多态性具有种族差异性。了解不同种族人群间血管紧张素转换酶基因多态性的遗传特点,是研究血管紧张素转换酶基因I/D多态性与疾病相关性的基础和前提。     

四川汉族人群15个短串联重复序列基因座遗传多态性分析

目的获得15个短串联重复(short tandem repeat,STR)基因座在四川汉族人群中的群体遗传学数据。方法654份血样采自四川地区无血缘关系的汉族个体。Chelex法提取DNA,PCR复合扩增,自动基因分析仪电泳,收集电泳结果数据,基因扫描分析软件计算扩增产物片段相对大小,基因分型软件进行样本基因型分型。结果全部样本的每个STR基因座都获得了清晰的基因型分型结果。15个STR基因座的基因型分布符合Hardy-Weinberg平衡。15个STR基因座的杂合度介于0.6101—0.8654之间。累计非父排除率和累计个人识别率为0.999998766和>0.999999999。结论经1次扩增电泳可获得15个STR基因座的基因型分型结果,累计非父排除率和累计个人识别率较高,适合作为四川汉族人群的遗传标记,用于人类学、疾病连锁分析、法医学亲权鉴定和个体识别等领域的研究。