Incidence of venous thromboembolism in first-degree relatives of patients with venous thromboembolism who have factor V Leiden

In families with inherited thrombophilia the risk of venous thromboembolism is dependent on the clinical phenotype of the proband

The utility of laboratory investigation of relatives of individuals with inherited thrombophilia is uncertain. To assess the risk of venous thromboembolism (VTE) among the carriers, we investigated a family cohort of 1,720 relatives of probands with thrombophilia who were evaluated because of VTE (n=1,088), premature arterial thrombosis (n=113), obstetric complication (n=257), or universal screening before pregnancy or hormonal contraception or therapy (n=262); 968 relatives were carriers of thrombophilia. A first deep venous thrombosis (DVT) occurred in 44 carriers and 10 non-carriers during 37,688 and 29,548 observationyears from birth, respectively. The risk of DVT among the carriers compared with non-carriers was estimated as a hazard ratio (HR). If the proband had VTE and factor V Leiden (FVL) and/or prothrombin (PT)20210A, the HR for DVT was 2.77 (95%CI 1.21–4.82) in the carriers overall, and 5.54 (95%CI 3.20–187.00) in those homozygous or double heterozygous for FVL and PT20210A. If the proband had VTE and a deficiency of antithrombin (AT), protein C or S, the HR for DVT was 5.14 (95%CI 0.88–10.03) in the carriers overall, and 12.86 (95%CI 2.46–59.90) in those with AT deficiency. No increase in risk was found among the carriers who were relatives of the probands who were evaluated for reasons other than VTE. In conclusion, familial investigation for inherited thrombophilia seems justified for probands with previous VTE, but appears of doubtful utility for the relatives of probands without VTE. This should be taken with caution regarding families with deficiency of natural anticoagulants, given the low number of cases analysed.

Interactions of established risk factors and a GWAS-based genetic risk score on the risk of venous thromboembolism

Multiple genetic and environmental risk factors contribute to venous thromboembolism (VTE) risk. Understanding how genes and environmental risk factors interact may provide key insight into the pathophysiology of VTE and may identify opportunities for targeted prevention and treatment. It was our aim to examine the main effects and the potential effect-modification between single nucleotide polymorphisms (SNPs) at established loci and lifestyle risk factors for VTE. We performed a nested case-control study using data on 1,040 incident VTE cases and 16,936 controls from the Nurses' Health Study, Nurses' Health Study II, and Health Professionals Follow-up Study cohorts, who gave blood, were selected as participants in a previous genome-wide association study (GWAS), and completed a biennial questionnaire at time of blood draw. We selected SNPs that were associated with VTE risk in previous GWAS studies. A genetic risk score (GRS) was constructed to evaluate the combined effect of the 16 SNPs that have reached genome-wide significance in previous GWAS of VTE. Interactions between SNPs and VTE risk factors (BMI and smoking) were also assessed. We found a significant association between our GRS and VTE risk. The risk of VTE among individuals in the highest GRS tertile was 2.02 times that of individuals in the lowest GRS tertile (p-trend = 9.69×10(-19)). The OR was 1.52 (p=1.03×10(-8)) for participants in the highest GRS tertile compared to those in the medium GRS tertile. However, while BMI and smoking were associated with VTE, and their effects were additive to each other we did not observe any significant multiplicative gene-environment interactions.

[Venous thromboembolism and pregnancy]

Venous thromboembolism (VTE) is a major cause of maternal morbidity and mortality during or early after pregnancy. Prior VTE or family history of VTE, clinical or biological risk factors increased the risk of pregnancy-related VTE. Defining the risk of VTE before or at the beginning of pregnancy is necessary to propose the best prevention. However, the management is not standardized between physicians, centres and countries. Current guidelines for prophylaxis and treatment of VTE are discussed in this review.

Risk assessment of venous thrombosis in families with known hereditary thrombophilia: the MARseilles-NImes prediction model

BACKGROUND

Although predicting the risk of venous thrombosis (VT) in an individual from a family with inherited thrombophilia is of major importance, it is often not feasible.

OBJECTIVES

To develop a simple risk assessment model that improves prediction of the risk of VT for individuals of families with inherited thrombophilia.

PATIENTS/METHODS

1201 relatives from 430 families with inherited thrombophilia (deficiencies of antithrombin, protein C or protein S, and the factor V Leiden and F2 20210A mutations) were recruited at the referral center for thrombophilia in Marseilles, France, from 1986 to 2008. One hundred and twenty-two individuals had a personal history of VT. Sixteen preselected clinical and laboratory variables were used to derive the VT risk score.

RESULTS

The scores based on the 16 variables and on the five most strongly associated variables performed similarly (areas under receiver operating characteristic curves of 0.85 and 0.83, respectively). For the five-variable score, named the MARNI score, derived from family history score of VT, von Willebrand factor antigen levels, age, severity of thrombophilia, and FGG rs2066865, the risk of VT ranged from 0.2% for individuals with a score of 0 (n = 186) to > 70% for individuals with a score of ≥ 7 (n = 27). The model was validated with an internal bootstrap method.

CONCLUSIONS

With the use of a simple scoring system, assessment of the risk of VT in subjects from families with inherited thrombophilia can be greatly improved. External validation is now needed to replicate these findings.

ABO blood group and von Willebrand factor levels partially explained the incomplete penetrance of congenital thrombophilia

OBJECTIVE

We aimed to study the association among ABO blood group, von Willebrand factor, factor VIII plasma levels, and the risk of venous thrombosis (VT) in a cohort of 1774 relatives from 500 families with inherited thrombophilia.

METHODS AND RESULTS

One hundred sixty-one of the 1774 relatives had a VT. Different risk groups were formed: no, low-(factor V Leiden or F2G20210A heterozygous carriers), and high-risk thrombophilia (antithrombin, protein C, protein S, factor V Leiden, or F2G20210A homozygous carriers and combined defects). Compared with group O, AB blood group was associated with increased risk of VT: hazard ratio (HR)=3.8 (2.0-7.2). The effect of blood group A and B was milder (HR=1.6 [1.1-2.5] and 1.8 [1.0-3.3], respectively). An increased risk of VT was observed with increasing levels of von Willebrand factor and factor VIII plasma levels (HR=2.96 [1.92-4.56] and HR=2.60 [1.92-4.56] for third versus first tertile of von Willebrand factor and factor VIII plasma levels, respectively). In multivariate analysis, AB group (HR=2.3 [1.1-4.8]), high-risk thrombophilia (HR=2.8 [1.6-4.6]), and high von Willebrand factor levels (HR=2.3 [1.3-4.0]) were significantly associated with increased risk of VT. The risk of VT in individuals with high-risk thrombophilia and AB group was 14.4× higher than in those without thrombophilia and O group (5.0-41.4).

CONCLUSIONS

ABO blood group modifies the risk of VT in families with hereditary thrombophilia. Phenotyping of the ABO blood group should be performed to better assess the risk of VT in asymptomatic individuals from thrombophilic families.

Recommendations for the prevention of pregnancy-associated venous thromboembolism

Pregnancy is a risk factor for venous thromboembolism (VTE), an important cause of maternal morbidity and mortality. Although there is a 4-5-fold increased risk compared to that of nonpregnant women of the same age, the absolute risk is low at no more than two episodes of VTE per 1000 pregnancies. There is uncertainty about which women require thromboprophylaxis during pregnancy or postpartum because of a lack of data from appropriate clinical trials. For this reason, recommendations for prophylaxis should be made only after explaining the available evidence to the patient and taking into account her perception of the balance of risk and benefit in thromboprophylaxis. The aim of these recommendations is to provide clinicians with practical advice to assist in decisions regarding thromboprophylaxis in women considered to be at risk of VTE during pregnancy and the postpartum. The authors are clinicians from across New Zealand and Australia representing the fields of haematology, obstetric medicine, anaesthesiology, maternal-fetal medicine and obstetrics. Authors were invited to review the relevant literature and then worked collaboratively to devise recommendations and resolve areas of controversy. The recommendations contained herein were reached by consensus and represent the opinion of the panel. The absence of randomised clinical trials in this area limits the strength of evidence that can be used, and it is acknowledged that they represent level C evidence. The panel advocates for appropriate clinical studies to be carried out in this patient population to address the inadequacy of present evidence.

Predictors of thrombosis in relatives of patients with venous thromboembolism

PURPOSE OF REVIEW

Hereditary and acquired risk factors contribute to the development of venous thromboembolism (VTE). Relatives of patients who have a hereditary predisposition to thrombosis ('hereditary thrombophilia') will have a heightened risk of VTE if they share the same thrombophilic abnormality. However, if patients do not have a currently recognized thrombophilia it cannot be assumed that their relatives have a normal risk of thrombosis; the patient and their relatives may have a yet to be discovered hereditary abnormality.

RECENT FINDINGS

A recent study by our group suggests that the relatives of patients with unprovoked VTE at a young age (e.g. <45 years) have a substantially higher risk [odds ratio (OR) 3.3; 95% confidence interval (CI) 1.7-6.4] of developing VTE than the relatives of older patients with unprovoked VTE (e.g. >71 years). This effect occurred independently of whether patients had a currently recognized hereditary thrombophilia.

SUMMARY

Relatives of patients with unprovoked VTE have an increased risk of VTE. Testing for thrombophilia in the patients, and in the relatives of the patients who have a thrombophilia, allows the risk of thrombosis in the relatives to be estimated. Thrombosis at a young age appears to be an additional independent risk factor for a heightened risk of thrombosis in patients' relatives.

Usefulness of factor V Leiden mutation testing in clinical practice

We have investigated the clinical usefulness of the activated protein C resistance (APCR)/factor V Leiden mutation (FVL) test by sending out questionnaires to all Norwegian physicians who ordered these tests from our publicly funded service laboratory during a 3-month period, and of whom 70% (267/383) responded. Indications for testing, patient follow-up, the use of APCR versus FVL tests and differences in practice between hospital doctors and GPs were examined. We found that 46% of the tests were predictive, ordered for risk assessment in healthy individuals with no previous history of venous thromboembolism (VTE). Among these, 42% of the tests were taken on the initiative of the patient and 24% were screening tests before prescription of oral contraceptives. In total, 54% of the tests were classified as diagnostic, among which 42% were ordered owing to a previous history of VTE and 22% to a history of brain stroke or myocardial infarction. The prevalence of FVL heterozygotes was not significantly different between the predictive and diagnostic test groups, that is, 26 and 20%, respectively. Only the predictive tests influenced patient follow-up. Here, the physician's advice to patients depended on the test result. In general, the clinical usefulness of APCR/FVL testing was low. Many tests were performed on unsubstantiated or vague indications. Furthermore, normal test results led to unwarranted refrain from giving advice about antithrombotic measures, leading to potential harm to the patient.

An evaluation of candidate genes of inflammation and thrombosis in relation to the risk of venous thromboembolism: The Women's Genome Health Study

BACKGROUND

Although pathways associated with hemostasis and thrombosis are well documented to have an impact on venous thromboembolism (VTE), whether the inflammatory cascade also influences VTE risk is uncertain.

METHODS AND RESULTS

We evaluated 51 polymorphisms from 32 inflammation-related genes (and an additional 19 polymorphisms from 15 thrombosis-related genes) as potential determinants of VTE in a prospective cohort of 22 413 white women followed over a 10-year period. Hazard ratios (HRs) for incident VTE according to the different genotypes were assessed by Cox proportional-hazards models. The false discovery rate (FDR) was used for correction for multiple testing with a 0.20 cut point. During follow-up, 158 idiopathic and 180 secondary VTE events occurred. As anticipated, factor V Leiden (HR, 3.22; 95% CI, 1.92 to 5.40; P<0.0001; FDR=0.004) and the prothrombin mutation (HR, 2.57; 95% CI, 1.64 to 4.02; P<0.0001; FDR=0.004) were both strongly associated with incident idiopathic VTE, as was the rs6046 polymorphism in the factor VII gene (HR, 0.54; 95% CI, 0.35 to 0.86; P=0.008; FDR, 0.12). With regard to polymorphism in the inflammatory genes, variation at rs1143634 in the IL-1beta gene was associated with a reduced risk of idiopathic VTE (HR, 0.59; 95% CI, 0.44 to 0.80; P=0.0007; FDR=0.02), whereas variation at rs1800872 in the IL-10 gene was associated with increased risk (HR, 1.42; 95% CI, 1.12 to 1.80; P=0.004; FDR=0.07). By contrast, no significant associations were found for secondary VTE events.

CONCLUSIONS

In addition to previously reported polymorphisms associated with hemostasis and thrombosis, these prospective cohort data suggest that genetic variation in IL-1 beta and IL-10 genes may also influence the risk of idiopathic VTE.

The utility of thrombophilia testing in pregnant women with thrombosis: fact or fiction?

Women who either present with an episode of acute venous thrombosis in pregnancy or who have a history of venous thrombosis who present for prenatal care often undergo testing for inherited thrombophilia. The rationale for screening may include questions about whether screening for inherited thrombophilias can help to alter anticoagulation plans in a pregnancy complicated by venous thrombosis, whether patients with a history of venous thrombosis who present for care in a subsequent pregnancy require anticoagulation and at what intensity, whether knowledge of thrombophilia changes the duration and intensity of anticoagulation outside pregnancy, and whether screening of family members is warranted. Data regarding these issues are reviewed, controversies surrounding thrombophilia testing in this setting are discussed, and clinical recommendations are made.

Thrombosis and inflammatory bowel disease-the role of genetic risk factors

Thromboembolism is a significant cause of morbidity and mortality in patients with inflammatory bowel disease (IBD). Recent data suggest thromboembolism as a disease-specific extraintestinal manifestation of IBD, which is developed as the result of multiple interactions between acquired and genetic risk factors. There is evidence indicating an imbalance of procoagulant, anticoagulant and fibrinolytic factors predisposing in thrombosis in patients with IBD. The genetic factors that have been suggested to interfere in the thrombotic manifestations of IBD include factor V Leiden, factor II (prothrombin, G20210A), methylenetetrahydrofolate reductase gene mutation (MTHFR, 6777T), plasminogen activator inhibitor type 1 (PAI-1) gene mutation and factor XIII (val34leu). In this article we review the current data and future prospects on the role of genetic risk factors in the development of thromboembolism in IBD.