Genetic Associations With Stable Warfarin Dose Requirements in Han Chinese Patients

ABSTRACT

Warfarin is a commonly prescribed anticoagulant for valvular heart disease that plays an important role in clinical management to prevent thrombotic events. In this study, we aim to perform a comprehensive study to investigate the genetic biomarkers of stable warfarin dose in the Han Chinese population. We performed an integrative study on 211 Han Chinese patients with valvular heart disease. A total of 40 single nucleotide polymorphisms (SNPs) in 10 important genes (CYP2C9, VKORC1, ABCB1, CYP4F2, APOE, PROC, GGCX, EPHX1, CALU, and SETD1A) which are involved in the warfarin metabolic pathway and equilibrium of coagulation and anticoagulation were selected. We applied MassARRAY technology to genotype the 40 SNPs identified in these Han Chinese patients. Our results showed that 13 SNPs on 6 genes (CYP2C9, VKORC1, ABCB1, PROC, EPHX1, and SETD1A) were associated with the individual stable warfarin dose. Two VKORC1 SNPs (rs9934438 and rs2359612) were the strongest genetic factors determining warfarin dose requirements (P = 8 × 10-6 and 9 × 10-6, respectively). Rs4889599 in SETD1A was first reported to be associated with warfarin dose at a significant level of 0.001 in our study (Padjust = 0.040 after Bonferroni correction). We discovered that genetic variants in CYP2C9, VKORC1, ABCB1, PROC, EPHX1, and SETD1A may affect the stable warfarin dose requirement in Han Chinese patients with valvular disease. The discovery of these potential genetic markers will facilitate the development of advanced personalized anticoagulation therapy in Han Chinese patients.

Correlation between P-selectin rs1800807 and rs1800808 Gene polymorphisms and plasma soluble P-selectin concentrations in patients with atrial fibrillation complicated with thromboembolism in Xinjiang, China

This study is to investigate the relationship of P-selectin (Ps) gene rs1800807 and rs1800808 polymorphisms with plasma soluble P-selectin (sPs) in Han, Uygur, and Kazakh people with atrial fibrillation (AF) and thromboembolism (TE) in Xinjiang, China.A total of 778 Han patients (including 131 patients with AF and TE, 229 patients with AF and 418 healthy individuals), 660 Uygur patients (including 118 patients with AF and TE, 232 patients with AF and 310 healthy individuals), and 505 Kazakh patients (including 42 patients with AF and TE, 156 patients with AF and 307 healthy individuals) were enrolled in this study. Polymerase chain reaction-restriction fragment length polymorphism and direct DNA sequence analysis were used to analyze the polymorphisms of rs1800807 and rs1800808 of Ps gene. ELISA was used to determine the plasma sPs level. The association between plasma sPs levels and Ps gene polymorphisms was further analyzed.The sPs concentrations of GG genotype at rs1800807 locus in the Han, Uygur and Kazakh ethnic groups in Xinjiang, China were significantly higher than those of the CC genotype and CG genotype (P < .05). In the rs1800808 locus, plasma sPs concentrations of the heterozygous mutant CT genotypes in Han and Uygur populations were significantly higher than those in the CC and TT genotypes, whereas the plasma sPs concentrations in Kazakh TT genotypes were significantly higher than those in the CC and CT genotypes (P < .05). Among different ethnic groups, there were significant differences in sPs levels of rs1800807 and rs1800808 genotypes (P < .05).Plasma sPs concentrations are associated with Ps genotypes and sPs concentration of the same genotype shows racial differences.

Racial and gender differences in the incidence of recurrent venous thromboembolism

Men have been reported to have a higher incidence of recurrent venous thromboembolism than women. However, it is not known if this gender effect holds among different racial/ethnic groups and for both venous thrombosis and pulmonary embolism. We conducteda retrospective analysis of 18-to 65-year-old Caucasian, African-American and Hispanic cases hospitalized in California with unprovoked venous thromboembolism. The principal outcome was recurrent venous thromboembolism 7–60 months after the index event. Among 11,514 cases that were followed for a mean of 3.0 years, men had a significantly higher rate (events/100 patient-years) of recurrent venous thromboembolism than women for both venous thrombosis [rate ratio (RR)=1.5, 95% confidence interval (CI):1.3–1.8] and pulmonary embolism [RR=1.3, 95%CI:1.0–1.6].Among men the recurrence rate did not vary significantly between the racial/ethnic groups (p>0.05). However, the recurrence rate among Hispanic women with venous thrombosis was significantly higher than in Caucasian women (p<0.001) and was comparable to the rate in men. Both Hispanic and African-American women with pulmonary embolism had a higher recurrence rate compared with Caucasian women (p<0.02) that was comparable to the rate in men. We conclude that women in California had a 40% lower risk of recurrent venous thromboembolism compared to men. Rates were comparable among men of different races, but there were significant inter-racial differences among women, which also varied with the type of initial event. The effect of gender on the risk of recurrent venous thromboembolism can not be generalized because it varies between racial/ethnic groups and with the type of index event.

Integrated analysis of genetic variation and gene expression reveals novel variant for increased warfarin dose requirement in African Americans

Essentials Genetic variants controlling gene regulation have not been explored in pharmacogenomics. We tested liver expression quantitative trait loci for association with warfarin dose response. A novel predictor for increased warfarin dose response in African Americans was identified. Precision medicine must take into account population-specific variation in gene regulation.

SUMMARY

Background Warfarin is commonly used to control and prevent thromboembolic disorders. However, because of warfarin's complex dose-requirement relationship, safe and effective use is challenging. Pharmacogenomics-guided warfarin dosing algorithms that include the well-established VKORC1 and CYP2C9 polymorphisms explain only a small proportion of inter-individual variability in African Americans (AAs). Objectives We aimed to assess whether transcriptomic analyses could be used to identify regulatory variants associated with warfarin dose response in AAs. Patients/Methods We identified a total of 56 expression quantitative trait loci (eQTLs) for CYP2C9, VKORC1 and CALU derived from human livers and evaluated their association with warfarin dose response in two independent AA warfarin patient cohorts. Results We found that rs4889606, a strong cis-eQTL for VKORC1 (log10 Bayes Factor = 12.02), is significantly associated with increased warfarin daily dose requirement (β = 1.1; 95% confidence interval [CI] 0.46 to 1.8) in the discovery cohort (n = 305) and in the replication cohort (β = 1.04; 95% CI 0.33 -1.7; n = 141) after conditioning on relevant covariates and the VKORC1 -1639G>A (rs9923231) variant. Inclusion of rs4889606 genotypes, along with CYP2C9 alleles, rs9923231 genotypes and clinical variables, explained 31% of the inter-patient variability in warfarin dose requirement. We demonstrate different linkage disequilibrium patterns in the region encompassing rs4889606 and rs9923231 between AAs and European Americans, which may explain the increased dose requirement found in AAs. Conclusion Our approach of interrogating eQTLs identified in liver has revealed a novel predictor of warfarin dose response in AAs. Our work highlights the utility of leveraging information from regulatory variants mapped in the liver to uncover novel variants associated with drug response and the importance of population-specific research.

Predictors of warfarin dose requirements in South African patients attending an anticoagulation clinic

INTRODUCTION

Warfarin is the most common oral anticoagulant for the treatment and prevention of thromboembolic disease. However, it has a wide interpatient variability in dose requirements due to various genetic and clinical factors.

MATERIALS AND METHODS

This study investigated the effect of clinical and genetic factors on the variability of warfarin dose requirements in 147 South African patients (81 white and 66 black). The study was performed at a University Hospital Anticoagulation Clinic managed by nursing sisters at the Charlotte Maxeke Johannesburg Academic Hospital.

RESULTS

The most common indication for anticoagulation was atrial fibrillation (n = 55, 37.4%). The mean warfarin dose was significantly higher in black patients as compared to white patients (5.4 ± 2.9 mg/day and 3.8 ± 2.1 mg/day, respectively; P < 0.001). Older age was significantly associated with a lower maintenance warfarin dose (P < 0.001). Drugs which decreased the international normalized ratio (INR) were significantly associated with a higher maintenance warfarin dose of 6.4 ± 3.4 mg/day (P < 0.034). In contrast, there was no significant difference in warfarin dosage requirements in the presence of CYP2C9 and VKORC1 variant alleles (P > 0.05). Patients, however, homozygous for CYP2C9 *1,*3, and VKORC1 required less than 5 mg/day of warfarin to maintain the INR within the therapeutic range.

CONCLUSION

In conclusion, this study indicates that clinical characteristics including; age, ethnic group, and drugs which decrease the INR might help to predict better dose requirements in this population group and thereby reduce the risk of bleeding and thrombotic complications.

Anticoagulation intensity of rivaroxaban for stroke patients at a special low dosage in Japan

OBJECTIVES

In Japan, low-dose rivaroxaban [15 mg QD/10 mg QD for creatinine clearance of 30-49 mL/min] was approved for clinical use in NVAF patients partly because of its unique pharmacokinetics in Japanese subjects. The aim of the study was to determine the anticoagulation intensity of rivaroxaban and its determinant factors in Japanese stroke patients.

METHODS

Consecutive stroke patients with NVAF admitted between July 2012 and December 2013 were studied. Prothrombin time (PT), activated partial thromboplastin time (aPTT), and estimated plasma concentration of rivaroxaban (Criv) based on an anti-factor Xa chromogenic assay were measured just before and 4 and 9 h after administration at the steady state level of rivaroxaban. Determinant factors for Criv were explored using a linear mixed-model approach.

RESULTS

Of 110 patients (37 women, 75±9 years old), 59 took 15 mg QD of rivaroxaban and 51 took 10 mg QD. Criv at 4 h was 186 ng/mL for patients taking 15 mg QD and 147 ng/mL for those taking 10 mg QD. Both PT and aPTT were positively correlated with Criv. Criv was 72% lower at 4 h in 15 patients receiving crushed tablets than in the other patients, and tablet crushing was significantly associated with lower Criv (adjusted estimate -0.43, 95% CI -0.60 to -0.26) after multivariate-adjustment.

CONCLUSION

The anticoagulation effects of rivaroxaban in the acute stroke setting for Japanese NVAF patients were relatively low as compared with those in the ROCKET-AF and J-ROCKET AF trials. Tablet crushing, common in dysphagic patients, decreased Criv.

Practical management approaches to anticoagulation non-compliance, health literacy, and limited English proficiency in the outpatient clinic setting

Warfarin is a widely used oral anticoagulant. It is highly efficacious for the treatment and prevention of thromboembolic disorders despite its narrow therapeutic window. Poor compliance with warfarin is common and a major contributor to poor anticoagulation control. A number of psychosocial issues (e.g. depressive symptoms, attitudinal and behavioral factors, cognitive function, lack of social support, limited English proficiency, health illiteracy) have been associated with warfarin non-compliance among patients in anticoagulation clinics. Patient-specific features, such as these, are important to identify in order to develop appropriate and practical interventions. Health literacy and limited English proficiency are the extension of issues related to culture, language, and ethnicity. A better understanding of patients' functioning level and health utilization factors may help to develop and target interventions for high risk patients and reduce complications from suboptimal therapy and poor warfarin management due to non-compliance. Four patient case scenarios will be used to illustrate these issues and identify potential interventions to optimize warfarin therapy.

The effect of CYP2C9, VKORC1 genotypes and old age on warfarin pharmacologic sensitivity in korean patients with thromboembolic disease

The therapeutic dose of warfarin is dependent upon intrinsic patient characteristics that are highly variable. We assessed the effects of CYP2C9, VKORC1 1173 C/T polymorphisms, and old age on warfarin dosing and sensitivity by measuring plasma S-/R-warfarin levels in Korean patients. INR and the plasma S-/R-warfarin concentrations were determined in 58 patients who had the VKORC1 1173C/T CYP2C9 genotypes, were on a long-term anticoagulation regimen with warfarin, and took a daily dose of warfarin. The pharmacokinetic sensitivity of warfarin was significantly higher in the CYP2C9 *1/*3 genotypes than in the CYP2C9 *1/*1 genotypes [ratio of S-warfarin concentration/dose, 0.53 vs. 0.21; p=0.01]. Pharmacodynamic sensitivity in older patients (≥ 75 years) with the CYP2C9 *1/*1 and VKORC1 1173 TT genotypes was significantly higher as compared to younger patients (<75 years) [Ratio of INR/S-warfarin concentration, 4.88 vs. 3.41; p = 0.026]. The CYP2C9*3 allele and old age (≥ 75 years) with the VKORC1 1173 T allele were also associated with increased risk of over-anticoagulation. The increase of over-anticoagulation risk and warfarin sensitivity is related to the CYP2C9*3 allele and old age with the VKORC1 1173 T allele in Korean patients with thromboembolic disease. These findings suggest that a lower initial and maintenance dose should be considered for the patients with CYP2C9 *3 allele and advanced age in this patient population. However, due to the limited number of patients in the study population, our finding needs to be confirmed by a larger, well-controlled study.

Risk of thromboembolic complications after intracerebral hemorrhage according to ethnicity

INTRODUCTION

Incidence of thromboembolic (TE) disease varies with race and ethnicity yet little is known about whether these differences also apply to the poststroke period. We review the literature and compare published data with observations from two recent global trials on intracerebral hemorrhage (ICH).

METHODS

A systematic review of the literature in EMBASE/Medline identified relevant articles. Published data were compared to the TE events--myocardial infarction (MI), cerebral infarction (CI), deep venous thrombosis (DVT), and pulmonary embolism (PE)--observed among placebo patients in two trials investigating the efficacy and safety of recombinant factor VIIa (rFVIIa) (Novo Nordisk A/S, Denmark) in the treatment of spontaneous ICH. The relative risk of TE complications after ICH was estimated for blacks/African Americans and Asians after adjustment for relevant risk factors.

RESULTS

Only four relevant studies on TE disease after stroke were identified with data limited to poststroke MI and CI in a mixture of ischemic stroke and ICH patient populations. In the literature, blacks/African Americans appear to have a lower incidence rate of cardiac and cerebro-vascular complications after stroke, and Asians have a higher incidence rate of recurrent strokes, compared with Caucasians. In the two global trials, the overall poststroke incidence rates of MI, CI, DVT, and PE at 3 months after ICH onset were 2.3%, 2.0%, 3.7%, and 1.1%, respectively. After adjustment for differences in baseline risk factors, blacks/African Americans had a significantly higher risk of developing DVT compared with Caucasians (OR=5.64, P=0.0334), while Asians had a strong trend toward a higher risk of DVT (odds ratio=3.22, P=0.0932). The adjusted relative risk of PE, CI, and MI was not significantly different across ethnicities.

CONCLUSION

This is the first study to specifically examine the risk of TE complications in the post-ICH period according to ethnicity. In a limited ICH population, we observed a significantly higher risk of DVT in blacks/African Americans compared with Caucasians after adjustment for differences in risk factors. We observed nonsignificant trends toward differences in the relative risk of MI, CI, or PE across ethnicities.

African American race was associated with an increased risk of complications following venous thromboembolism

OBJECTIVE

Limited data exist on the quality of care for patients with venous thromboembolism (VTE), and it is unknown whether the processes and outcomes of care for this illness differ between African Americans and whites.

STUDY DESIGN AND SETTING

We retrospectively studied 168 patients hospitalized for VTE in two Veterans Affairs hospitals during fiscal years 2000-2002. Patient characteristics, information about processes of care, and medical outcomes at 90 days after the index VTE event were abstracted from medical records. We used logistic regression to explore associations between race, processes of care, and the overall 90-day complication rate (i.e., death, bleeding, or recurrent VTE), adjusting for patient baseline characteristics.

RESULTS

Multivariable analysis demonstrated that administration of warfarin within 1 day of starting heparin (odds ratio [OR] 0.20, 95% confidence interval [CI]: 0.05-0.42) and overlap of heparin and warfarin treatment >or=4 days (OR 0.09, 95% CI: 0.02-0.50) were associated with a lower complication rate, and African American race was associated with a higher complication rate (OR 5.2, 95% CI: 1.3-21.6). Race was not significantly associated with the performance of processes of care in multivariable analysis.

CONCLUSION

Although African Americans had an increased risk of complications following VTE, race was not independently associated with the use of processes of care for VTE.

Management of Chinese patients on warfarin therapy in two models of anticoagulation service - a prospective randomized trial

AIM

To compare the treatment outcomes of a clinical pharmacist-managed anticoagulation service with physician-managed service in Chinese patients.

METHODS

A prospective, randomized clinical trial was conducted at the anticoagulation clinic of a teaching hospital in Hong Kong. Patients aged > or = 18 years who would required warfarin therapy for at least 3 months were recruited. Patients were randomized to the pharmacist-managed or physician-managed group. Primary clinical outcome was assessed by the percentage of patient time spent within the target international normalized ratio (INR) range. The incidence of major thromboembolic events (TEs) and major bleeding was assessed as secondary clinical outcomes. The cost per patient per month (cPPPM) was calculated and patient satisfaction was assessed by patient satisfaction questionnaire (PSQ)-18.

RESULTS

One hundred and forty-one patients were recruited at the anticoagulation clinic and 137 patients completed the study. Patients in the pharmacist-managed group (n = 68) were in the target INR 64% of patient time vs. 59% in the physician-managed group (n = 69) (P < 0.001). There was no significant difference in incidence of major TEs or bleeding. The cPPPM in the pharmacist-managed group (76 +/- 95 US dollar) (43 +/- 53 British pound) was lower than in the physician-managed group (98 +/- 158 US dollar) (55 +/- 89 British pound) (P < 0.001). The PSQ-18 score of the pharmacist-managed group (3.8 +/- 0.2) was higher than that of the physician-managed group (3.6 +/- 0.3) (P < 0.001).

CONCLUSION

The pharmacist-managed anticoagulation service was more effective and less costly than the physician-managed service in achieving target anticoagulation control for Chinese patients on warfarin therapy.

Antiplatelet therapy in populations at high risk of atherothrombosis

Atherothrombosis is the most common cause of an acute ischemic event. Antiplatelet agents form the cornerstone of atherothrombosis prevention. The purpose of this article is to review the use of antiplatelet agents in patients that are at particularly high risk of atherothrombotic events. To undertake this review, we searched the literature to identify key studies on the use of antiplatelet agents in this group of patients. Antiplatelet agents, such as aspirin and clopidogrel, play a fundamental role in the treatment and management of secondary thrombotic events. The routine use of aspirin is recommended, as it has been shown to reduce the risk of thrombotic events by approximately 25%. Additional benefit has been demonstrated with clopidogrel, both as a monotherapy and in combination with aspirin. In the CAPRIE trial, 19,185 patients with atherosclerotic vascular disease were randomized to receive clopidogrel (75 mg/day) or aspirin (325 mg/day) for a mean duration of follow-up of 1.91 years. Clopidogrel provided an additional 8.7% relative risk reduction in the primary composite endpoint of ischemic stroke, myocardial infraction or vascular death compared with aspirin. In the CURE trial, the addition of clopidogrel to background aspirin was associated with a 20% relative risk reduction in a composite of death from cardiovascular causes, nonfatal myocardial infarction or stroke compared with aspirin alone. In patients undergoing PCI as part of the PCI-CURE substudy, clopidogrel was associated with a 30% relative reduction in the incidence of cardiovascular events in the first 30 days after intervention compared with aspirin. The benefits of antiplatelet therapy continue to be investigated. Whether dual antiplatelet therapy is superior to aspirin monotherapy for high-risk primary prevention is unknown. The ongoing CHARISMA trial aims to determine the relative efficacies of aspirin monotherapy and aspirin/clopidogrel combination therapy in a broad range of high-risk patient populations. In addition, the REACH registry, a worldwide survey of symptomatic and high-risk patients, has been set up to provide vital epidemiological information regarding the risks of atherothrombosis in order to contribute to the development of better preventive strategies and management regimens for at-risk patients.

Incidence and risk factors for development of venous thromboembolism in Indian patients undergoing major orthopaedic surgery: results of a prospective study

INTRODUCTION

The incidence of venous thromboembolism (VTE) in Western populations undergoing major orthopaedic surgery without any thromboprophylaxis has been reported to range from 32% to 88%. There is however limited information on incidence of VTE in Indian patients and most of the Indian patients undergoing these surgeries do not receive any form of prophylaxis regardless of their risk profile.

METHODS

A prospective study was performed on 147 patients undergoing major orthopaedic surgery for total knee replacement (TKR), total hip replacement (THR), and proximal femur fracture fixation (PFF) without any prophylaxis. These patients were profiled for presence of the known risk factors responsible for development of VTE. A duplex ultrasound on both lower limbs was done 6 to 10 days after surgery. Twenty three patients underwent THR, 22 patients underwent TKR, and 102 underwent surgery for PFF. The patients were assessed clinically for any signs of deep venous thrombosis (DVT) and pulmonary embolism (PE). A helical CT scan was done in case of suspicion of PE and a duplex ultrasound was done in case of clinical suspicion of DVT irrespective of the stage of study.

RESULTS

The overall incidence of VTE was 6.12% and that of PE was 0.6%. The risk factors that were found to be significantly responsible for development of VTE (p < 0.05) were: immobility greater than 72 hours, malignancy, obesity, surgery lasting more than two hours.

CONCLUSION

The study reconfirms the belief that DVT has a lower incidence in Indian patients as compared with other ethnic groups.

Relationship of international normalized ratio to bleeding and thromboembolism rates in Taiwanese patients receiving vitamin K antagonist after mechanical valve replacement

BACKGROUND AND PURPOSE

Asians may be less vulnerable to thrombotic disease than Caucasians. Optimum international normalized ratio (INR) anticoagulant therapy guidelines for Asian populations remain to be established. This study investigated the risk factors for major bleeding or thromboembolism (TE) in Taiwanese patients receiving mechanical aortic and/or mitral valve replacement, including INR < or > 2.0.

METHODS

The records of 563 Taiwanese patients receiving mechanical aortic and/or mitral valve replacement between 1996 and 2001 were retrospectively studied. Patient follow-up data was divided into several 6-month periods: 6-month increments after surgery if no bleeding or TE occurred and the 6 months preceding the adverse event when an event occurred. Data including warfarin sodium dosage and estimated INR unit for each time period were collected and analyzed.

RESULTS

A total of 3,391 records were retrieved for analysis with an average follow-up period of 3.3 +/- 1.4 years. The mean warfarin sodium dose was 2.86 +/- 1.09 mg/day and the INR was 1.86 +/- 0.66. Major bleeding events occurred in 20 patients (1.07% per patient-year) and TE events in 38 patients (2.04% per patient-year), accounting for a 3.11% rate of overall events (bleeding or TE) per patient-year. Multivariate risk analysis revealed follow-up age > 60 years and receiving mitral valve replacement were risk factors for overall events (odds ratio = 1.84, p = 0.021 for follow-up age > 60 years; odds ratio = 1.36, p = 0.019 for receiving mitral valve replacement), while gender, double valve replacement, valve type, INR < 2.0, and atrial fibrillation were not.

CONCLUSIONS

Our data suggest that low-intensity anticoagulant therapy (INR < 2.0) in Taiwanese patients was not associated with increased TE and bleeding rates compared to higher intensity anticoagulant therapy. Follow-up age over 60 years and valve replacement at the mitral site were associated with increased rate of overall events.

Incidence and risk factors of thromboembolism in systemic lupus erythematosus: A comparison of three ethnic groups

OBJECTIVE

To compare the incidence and risk factors for thromboembolic events in systemic lupus erythematosus (SLE) patients of different ethnic backgrounds.

METHODS

SLE patients who were newly diagnosed or were referred within 6 months of diagnosis between 1996 and 2002 were prospectively followed up for the occurrence of thromboembolic events. Cumulative hazard and risk factors for thromboembolism were evaluated and compared among patients of different ethnic origins.

RESULTS

We studied 625 patients who fulfilled the American College of Rheumatology criteria for SLE (89% women): 258 Chinese, 140 African Americans, and 227 Caucasians. The mean +/- SD age at SLE diagnosis was 35.7 +/- 14 years. After a followup of 3,094 patient-years, 48 arterial events and 40 venous events occurred in 83 patients. The overall incidence of arterial and venous thromboembolism was 16/1,000 patient-years and 13/1,000 patient-years, respectively. The cumulative hazard of arterial events at 60 months after the diagnosis of SLE was 8.5%, 8.1%, and 5.1% for the Chinese, African Americans, and Caucasians, respectively. The corresponding cumulative risk of venous events was 3.7%, 6.6%, and 10.3%, respectively (P = 0.008 for Chinese versus Caucasians, by log rank test). Smoking, obesity, antiphospholipid antibodies, and use of antimalarial agents and exogenous estrogens were less frequent in the Chinese patients. In Cox regression models, low levels of high-density lipoprotein (HDL) cholesterol, Chinese ethnicity, oral ulcers, and serositis predicted arterial events, whereas male sex, low levels of HDL cholesterol, antiphospholipid antibodies, non-Chinese ethnicity, obesity, renal disease, and hemolytic anemia predicted venous events.

CONCLUSION

There are ethnic differences in the incidence of arterial and venous thromboembolism in patients with SLE that cannot be fully explained by the clinical factors studied. Further evaluation of other genetic and immunologic factors is warranted.

Contralateral Breast Cancer and Thromboembolic Events in African American Women Treated With Tamoxifen

BACKGROUND

Information about breast cancer treatment and prevention in African American women is scant, and recommendations for therapy from clinical trials for breast cancer are based primarily on data obtained from white women.

METHODS

We compared the effects of tamoxifen on risk of contralateral breast cancer and thromboembolic events in African American women and white women with a history of primary breast cancer. Data from 13 National Surgical Adjuvant Breast and Bowel Project clinical trials were pooled for analyses of time to contralateral breast cancer as a first event (eight trials and 10,619 patients) and of time to any thromboembolic phenomenon as a first event (all 13 trials and 20,878 patients). Risk factors for contralateral breast cancer and thromboembolic events among all women were determined using univariate proportional hazards models. (For each racial group, the rate of events associated with tamoxifen use was calculated as the ratio of the incidence rate with tamoxifen to that without tamoxifen.) Proportional hazards regression models were used to calculate 95% confidence intervals (CIs) and risk ratios. All statistical tests were two-sided.

RESULTS

Risk factors for contralateral breast cancer were body mass index (BMI) and lymph node positivity; those for thromboembolic events were BMI and age. In women of both ethnicities with estrogen receptor-positive breast cancer, those who took tamoxifen experienced a similar reduction in contralateral breast cancer (risk ratio for African American women = 0.74, 95% CI = 0.46 to 1.17, n = 690; risk ratio for white women = 0.76, 95% CI = 0.59 to 0.98, n = 9929; P = .92). Tamoxifen was also associated with an increase in thromboembolic events. The relative risk for thromboembolic events was higher in both African American and white women treated with tamoxifen and chemotherapy than in those who were treated with tamoxifen alone (risk ratio for African American women = 10.70, 95% CI = 5.94 to 19.28 versus 2.16, 95% CI = 1.26 to 3.71; n = 1842; risk ratio for white women = 15.49, 95% CI = 9.53 to 25.17 versus 3.13, 95% CI = 2.04 to 4.79, n = 19,036), and this effect was similar between the races (P = .10).

CONCLUSIONS

African American and white women appear to have the same risks of contralateral breast cancer and thromboembolic events in response to tamoxifen treatment.

Venous thromboembolic disease: comparison of the diagnostic process in blacks and whites

BACKGROUND

There has been concern that a disproportionate use of some health services exists among races. Whether this applies to patients with pulmonary embolism (PE) or deep venous thrombosis (DVT) has not been determined.

OBJECTIVE

To assess if there is a racial disparity in the application of diagnostic tests for PE or DVT, or in reaching a diagnosis or using medical facilities.

DESIGN

A study of cross-sectional samples of hospitalizations during 21 years using data from the National Hospital Discharge Survey.

SETTING

Noninstitutional hospitals in 50 states and the District of Columbia from January 1, 1979, through December 31, 1999.

PATIENTS

The National Hospital Discharge Survey abstracts demographic and medical information from the medical records of inpatients. For 1979 through 1999, the number of patients sampled ranged annually from 181 000 to 307 000. Measurements The number of sampled patients with DVT and with PE and the number of diagnostic tests performed were determined from the International Classification of Diseases, Ninth Revision, Clinical Modification codes at discharge. A multistage estimation procedure gave an estimate of values for the entire United States.

RESULTS

The age-adjusted rates of diagnosis of PE and of DVT per 100 000 population were not lower in blacks than in whites. Rates of use of radioisotopic lung scans, venous ultrasonography of the lower extremities, and contrast venography were comparable between races. The durations of hospitalization for patients with a primary discharge diagnosis of PE and of DVT were also comparable.

CONCLUSIONS

There is nothing to suggest that diagnostic tests are being withheld, and there is no evidence of a failure to reach a diagnosis in blacks with thromboembolic disease.

Thromboembolic risk factors in patients undergoing kidney transplant: implication of abnormally short activated partial thromboplastin time

This study was designed to examine the relationship of short activated partial thromboplastin time (aPTT) and prothrombin time (PT) to the incidence of thromboembolic events, hereditary and acquired coagulation defects associated with an increased risk of thrombosis, or cardiovascular diseases in patients undergoing renal transplantation. The prevalence of these conditions in our patients (n = 436) was 55%. Forty-two percent of the patients had short aPTT or PT. Multivariate analysis revealed that patients with short aPTT have an odds ratio (OR) = 2.15, 95% Confidence Interval (CI) (1.27-3.64) (p = 0.0042), and for patients with short PT, an OR = 2.01, 95% CI (0.99-4.08) (p = 0.052). Our study also suggests that other risk factors, including non-white ethnicity (98% blacks), OR = 1.64, 95% CI (1.01-2.67) (p = 0.047), diabetes mellitus, OR = 2.62, 95% CI (1.11-6.18) (P = 0.028), and autosomal dominant polycystic kidney disease (ADPKD) (p < 0.0001). Short aPTT results, or probably short PT results, pre- or post-transplantation may be associated with increased risks for thromboembolism.

Relationship of venous thromboembolism and myocardial infarction with the renin-angiotensin system in African-Americans

Genetic polymorphisms/mutations associated with venous thrombosis have largely been confined to the genes that encode for proteins in either the coagulant or the anticoagulant pathway. Although genetic alterations in the renin-angiotensin system have been reported to have a role in myocardial infarction and hypertension, there is recent evidence to suggest that there may also be an association with venous thrombosis. To extend our earlier observation of an association between the ACE DD genotype in African-American males and venous thrombosis, other genes in the renin-angiotensin pathway were investigated for possible disease association and were compared with African-Americans with myocardial infarction. African-American patients with a documented history of venous thrombosis or a history of myocardial infarction were eligible for participation as cases in the study. Control subjects were African-American outpatients attending a clinical laboratory for routine blood tests who had comparable age and gender distributions to the cases. Persons with a history of myocardial infarction, stroke, or thrombosis were excluded. Genes that were analyzed for known polymorphisms included angiotensinogen, angiotensin-converting enzyme (ACE), and the angiotensin II type I receptor. Our results showed that the ACE DD genotype was also associated with MI in African-American males but not in females. Racial/ethnic and sex differences were also found with respect to the genotype distribution of the ACE 4656(CT)(2/3) polymorphism. It was observed that the 2/2 genotype had a protective effective in males for myocardial infarction and venous thrombosis. The data also demonstrated that the allele frequencies of the A1166C variant of the angiotensin II type I receptor were different in African-Americans as compared to Caucasians.

Risk of hospitalized stroke in men enrolled in the Honolulu Heart Program and the Framingham Study: A comparison of incidence and risk factor effects

BACKGROUND AND PURPOSE

Risk of death due to stroke in Japan is more than double the risk in the United States. It remains unknown why some ethnic groups are more prone to stroke than others. Our purpose was to compare the 20-year incidence of hospitalized stroke between Japanese-American men in the Honolulu Heart Program and white men in the Framingham Study.

METHODS

This was a 20-year follow-up study beginning around 1965, a population-based study on the island of Oahu, Hawaii, and in Framingham, Mass. Participants were 7589 men in Honolulu and 1216 men in Framingham without prevalent coronary heart disease and stroke. Subjects were 45 to 68 years old when follow-up began. Main outcome measures were incident thromboembolic and hemorrhagic stroke.

RESULTS

Framingham men had a 40% excess of thromboembolic stroke compared with Honolulu men after adjustment for age and other risk factors (62/1000 versus 45/1000, respectively, P<0.001), whereas incidence of hemorrhagic stroke was nearly identical (14.8/1000). In both cohorts, each stroke type was consistently elevated in the presence of hypertension and cigarette smoking. Diabetes and body mass index increased the risk of thromboembolic stroke in both samples, and diabetes increased the risk of hemorrhagic events in Framingham. Alcohol intake and low total cholesterol were associated with hemorrhagic events in Honolulu but not in Framingham. Despite occasional differences in risk factor effects, none were significantly different between cohorts.

CONCLUSIONS

The incidence of thromboembolic stroke requiring hospitalization is markedly less in Honolulu than in Framingham. The difference in stroke incidence rates observed cannot be explained by the traditional risk factors. Further studies are needed to identify factors that protect Japanese-American men in Honolulu from stroke.

Venous thromboembolism in pregnant Chinese women

OBJECTIVE

To evaluate the incidence, disease pattern, and risk factors for thromboembolism in pregnant Chinese women.

METHODS

We conducted a study from January 1998 to December 2000. Women with thromboembolic diseases were identified and their case records retrieved and reviewed. Demographic characteristics were compared between women with and without thromboembolism.

RESULTS

Thirty-two women were diagnosed as having thromboembolic disease during the study period. The total number of deliveries over the study period was 16,993, giving an incidence of 1.88 per 1000 deliveries. There were two cases of pulmonary embolism and one resulted in a maternal death. The others had deep vein thrombosis of which over 80% were limited to calf veins only. The ultrasound examinations requested for suspected deep venous thrombosis before and after the event of maternal death were 1.62 and 10.7 per 1000 deliveries (P <.001); and the corresponding cases of deep venous thrombosis diagnosed were 0.29 and 2.94 per 1000 deliveries, respectively (P <.001). The majority (75%) of cases were diagnosed in the postpartum period, mainly after cesarean delivery. Women with venous thromboembolism were older, had higher body mass index, and a higher incidence of preeclampsia.

CONCLUSION

Thromboembolic disease is not uncommon among pregnant Chinese women. The incidence was similar to that of the white population, although the sites of vascular occlusion were different. The long-standing belief that thromboembolism is rare among Chinese is at least partly because of underdiagnosis.

The allele frequency of mutations in four genes that confer enhanced susceptibility to venous thromboembolism in an unselected group of New York State newborns

The frequencies of Factor V G1691A (FVL), prothrombin (PT) G20210A, 5'10'methylenetetrahydrofolate reductase (MTHFR) C677T, and methionine synthase (MS) A2756G (four mutations associated with an increased risk of venous thromboembolism [VTE]) were determined in a sample of approximately 1500 New York State residents. Dried blood spots from approximately equal numbers of Caucasians, African-Americans and Hispanics were anonymously obtained from the New York State Department of Health Newborn Screening Program. Following PCR amplification of dried blood spot DNA, allele-specific oligonucleotide hybridization was used to detect mutant alleles. The total number of individuals at increased genetic risk for VTE was 271 (17.5%) of the 1553 persons tested. Increased genetic risk was defined as the heterozygous state for FVL or PT and the homozygous state for the MTHFR or MS polymorphisms. Sixteen individuals had more than one genetic risk factor. The MS gene variant allele frequencies for African-Americans and Hispanics are the first to be reported. This report also provides an estimate of the variant PT allele in the largest group of Hispanics studied to date.

Racial background is a determinant of average warfarin dose required to maintain the INR between 2.0 and 3.0

Warfarin is a commonly used prophylactic agent for the prevention of thromboembolic disease. We hypothesized that racial background influenced warfarin dosage, and tested this by recording the international normalized ratio (INR) in 867 patients aged 40-90 routinely passing through our Anticoagulation Service whose target INR was 2-3. Mean (95% confidence interval) dose was 4.1 (4.0-4.2) mg/d in 737 Caucasians, 5.5 (4.9-6.1) mg/d in 72 Asians, and 6.7 (5. 8-7.6) mg/d in 58 Afro-Caribbeans (P < 0.05) between each group). In a subgroup of 302 (41 Asians, 22 Afro-Caribbeans, 239 Caucasians), body mass index did not influence warfarin use. Despite small numbers, we conclude that racial background, but not body mass index, is a determinant of warfarin dosage. The reasons for this could be genetic, cultural (diet related), or both.

Incidence of idiopathic deep venous thrombosis and secondary thromboembolism among ethnic groups in California

BACKGROUND

Few studies have compared the incidence of deep venous thrombosis among ethnic groups.

OBJECTIVE

To determine the incidence of deep venous thrombosis among ethnic groups.

DESIGN

Analysis of the linked California Patient Discharge Data Set from 1991 to 1994.

SETTING

California.

PATIENTS

17991 patients with idiopathic deep venous thrombosis (thrombosis without cancer or hospitalization within preceding 6 months) and 5573 patients with secondary thromboembolism (thromboembolism occurring within 3 months of seven different events).

MEASUREMENTS

Ethnicity was determined by using race as documented in the data set. For idiopathic deep venous thrombosis, standardized age- and sex-adjusted incidences were calculated. For secondary thromboembolism, proportional hazards modeling was done.

RESULTS

The annual incidence of idiopathic deep venous thrombosis per 1000000 persons older than 18 years of age was 230 for white persons, 293 for African Americans (rate ratio, 1.27 [95% CI, 1.07 to 1.51]), 139 for Hispanic persons (rate ratio, 0.60 [CI, 0.54 to 0.67]), and 60 for Asians and Pacific Islanders (rate ratio, 0.26 [CI, 0.22 to 0.30]). Compared with white persons, Asians and Pacific Islanders who developed secondary thromboembolism had a significantly lower relative risk (range, 0.22 to 0.61) for all seven conditions analyzed.

CONCLUSIONS

Compared with white persons, Asians and Pacific Islanders have a very low incidence of idiopathic deep venous thrombosis and a very low relative risk for secondary venous thromboembolism.

A prospective randomized study on the use of nadroparin calcium in the prophylaxis of thromboembolism in Korean patients undergoing elective total hip replacement

Because of the belief that post-operative deep vein thrombosis (DVT) is rare in Asian patients, thromboprophylaxis is not usually prescribed for surgical patients. This study reports an open multi-centre controlled study of the use of a low molecular weight heparin, nadroparin calcium (Fraxoparine Sanofi France), as opposed to no prophylaxis in 100 patients undergoing uncemented total hip replacement. The patients had bilateral venography performed preoperatively and 10 days after operation. Eight patients (16%) developed DVT in the control group of 50 patients and 1 (2%) in the treatment group, also of 50 patients. Pulmonary embolus occurred in 1 patient in the treatment group and in 3 in the control group. Intraoperative and postoperative blood loss did not differ significantly between the two groups. Our study suggests that the incidence of DVT in Asian patients, though somewhat less than in their Western counterparts, is still considerable. It confirms the safety and efficacy of nadroparin calcium in preventing post-operative DVT in patients undergoing elective total hip replacement.

The influence of high fat diet on the fibrinolytic activity

High fat diet containing 50% fat was given to 28 Chinese healthy volunteers for 3 days. Their mean age was 28.04 years with SD 5.53. Blood glucose, cholesterol, triglyceride (TG) and venous occlusion test (VOT) were determined before and after diet. Tissue plasminogen activator (tPA) and plasminogen activator inhibitor (PAI) were determined before and after VOT. After high-fat diet, blood glucose and cholesterol increased significantly (p = 0.031, 0.049 respectively), but other parameters did not. TPA increased significantly after VOT either before or after high-fat diet, but such increment was significantly less after high-fat diet (P < 0.05). In conclusion, the immediate effect of short-term high-fat diet included increased plasma levels of glucose and cholesterol, and impaired fibrinolytic response in stress condition.

High incidence of thrombophilia detected in Chinese patients with venous thrombosis

Venous thromboembolism is rare in Chinese. To determine the incidence and disease profile of thrombophilia in Chinese patients with thrombosis, 52 unselected Chinese patients with documented venous thrombosis were studied for the presence of thrombophilia. Levels of antithrombin III (AT III), protein C (PC) and protein S (PS) as well as the presence of acquired lupus anticoagulant (LA) and anticardiolipin antibody (ACA) were investigated. Thirty patients were found to be abnormal. These consisted of 5 AT III deficiencies, 9 PC deficiencies, 10 PS deficiencies, 1 combined PC & PS deficiency (all in the heterozygous range), and 5 patients with LA and/or ACA. When the patients with LA and/or ACA are excluded, the incidence of hereditary thrombophilia is 25/47 i.e. 53.2% which is much higher than those reported in studies of Caucasian patients selected under strict criteria. Family studies performed in 16 cases of hereditary thrombophilia revealed involvement in 11 cases (68.7%); a total of 36 heterozygous family members were affected, most of which remain asymptomatic. Although 35 events predisposing to thrombosis (27 pregnancies, 1 oral contraceptive consumption and 7 surgical operations) were identified among these index patients, and the heterozygous family members, thrombosis was observed on only 6 occasions (17.1%). The data suggest that pregnancy and surgery do not carry the same degree of thrombotic risk in Chinese as in the Caucasian population with heterozygous AT III, PC and PS deficiency.