Current knowledge on the genetics of incident venous thrombosis

Fibrinolysis biomarker, thrombin, and activated protein C level alterations after coagulation activation depend on type of thrombophilia and clinical phenotype

Background

Recently, we have shown alterations in the anticoagulant response to recombinant activated factor VII (rFVIIa)-induced coagulation activation in patients with thrombophilia.

Objectives

This study aimed to extend this in vivo model to fibrinolysis biomarkers.

Methods

This interventional in vivo study included 56 patients with thrombophilia and previous venous thromboembolism (VTE+), 38 without VTE (VTE-), and 35 healthy controls. Plasma levels of D-dimer, plasmin-α2-antiplasmin (PAP) complex, and plasminogen activator inhibitor-1 (PAI-1) were monitored for over 8 hours after rFVIIa infusion (15 μg/kg) along with thrombin markers and activated protein C (APC).

Results

Throughout cohorts, median PAP increased by 40% to 52% (P < 3.9 × 10-10) and PAI-1 decreased by 59% to 79% (P < 3.5 × 10-8). In contrast to thrombin-antithrombin (TAT) complex, which also increased temporarily (44% to 115%, P < 3.6 × 10-6), changes in PAP and PAI-1 did not reverse during the observation period. The area under the measurement-time curves (AUCs) of PAP and TAT, which are measures of plasmin and thrombin formation, respectively, were each greater in the VTE+ cohort than in healthy controls (median PAP-AUC = 0.48 vs 0.27 ng·h/L [P = .003], TAT-AUC = 0.12 vs 0.03 nmol·h/L [P = 2.5 × 10-4]) and were correlated with one another (r = 0.554). As evidenced by the respective AUCs, asymptomatic factor (F)V Leiden carriers showed less PAP formation (0.22 vs 0.41 ng·h/L, P = 9 × 10-4), more pronounced PAI-1 decline (0.10 vs 0.18 ng·h/L, P = .01), and increased APC formation (28.7 vs 15.4 pmol·h/L, P = .02) than those within the VTE+ group (n = 19 each).

Conclusion

rFVIIa-induced thrombin formation is associated with fibrinolysis parameter changes outlasting the concomitant anticoagulant response. Both correlate with thrombosis history in FV Leiden and might help explain its variable clinical expressivity.

Elevated plasma complement factor H related 5 protein is associated with venous thromboembolism

Venous thromboembolism (VTE) is a common, multi-causal disease with potentially serious short- and long-term complications. In clinical practice, there is a need for improved plasma biomarker-based tools for VTE diagnosis and risk prediction. Here we show, using proteomics profiling to screen plasma from patients with suspected acute VTE, and several case-control studies for VTE, how Complement Factor H Related 5 protein (CFHR5), a regulator of the alternative pathway of complement activation, is a VTE-associated plasma biomarker. In plasma, higher CFHR5 levels are associated with increased thrombin generation potential and recombinant CFHR5 enhanced platelet activation in vitro. GWAS analysis of ~52,000 participants identifies six loci associated with CFHR5 plasma levels, but Mendelian randomization do not demonstrate causality between CFHR5 and VTE. Our results indicate an important role for the regulation of the alternative pathway of complement activation in VTE and that CFHR5 represents a potential diagnostic and/or risk predictive plasma biomarker.

Proteomics in thrombosis research

A State of the Art lecture titled “Proteomics in Thrombosis Research” was presented at the ISTH Congress in 2021. In clinical practice, there is a need for improved plasma biomarker‐based tools for diagnosis and risk prediction of venous thromboembolism (VTE). Analysis of blood, to identify plasma proteins with potential utility for such tools, could enable an individualized approach to treatment and prevention. Technological advances to study the plasma proteome on a large scale allows broad screening for the identification of novel plasma biomarkers, both by targeted and nontargeted proteomics methods. However, assay limitations need to be considered when interpreting results, with orthogonal validation required before conclusions are drawn. Here, we review and provide perspectives on the application of affinity‐ and mass spectrometry‐based methods for the identification and analysis of plasma protein biomarkers, with potential application in the field of VTE. We also provide a future perspective on discovery strategies and emerging technologies for targeted proteomics in thrombosis research. Finally, we summarize relevant new data on this topic, presented during the 2021 ISTH Congress.

Combined Oral Contraceptives and Venous Thromboembolism: Review and Perspective to Mitigate the Risk

Many factors must be considered and discussed with women when initiating a contraceptive method and the risk of venous thromboembolism (VTE) is one of them. In this review, we discuss the numerous strategies that have been implemented to reduce the thrombotic risk associated with combined oral contraceptives (COCs) from their arrival on the market until today. Evidences suggesting that COCs were associated with an increased risk of VTE appeared rapidly after their marketing. Identified as the main contributor of this risk, the dosage of the estrogen, i.e., ethinylestradiol (EE), was significantly reduced. New progestins were also synthetized (e.g., desogestrel or gestodene) but their weak androgenic activity did not permit to counterbalance the effect of EE as did the initial progestins such as levonorgestrel. Numerous studies assessed the impact of estroprogestative combinations on hemostasis and demonstrated that women under COC suffered from resistance towards activated protein C (APC). Subsequently, the European Medicines Agency updated its guidelines on clinical investigation of steroid contraceptives in which they recommended to assess this biological marker. In 2009, estradiol-containing COCs were marketed and the use of this natural form of estrogen was found to exert a weaker effect on the synthesis of hepatic proteins compared to EE. In this year 2021, a novel COC based on a native estrogen, i.e., estetrol, will be introduced on the market. Associated with drospirenone, this preparation demonstrated minor effects on coagulation proteins as compared with other drospirenone-containing COCs. At the present time, the standard of care when starting a contraception, consists of identifying the presence of hereditary thrombophilia solely on the basis of familial history of VTE. This strategy has however been reported as poorly predictive of hereditary thrombophilia. One rationale and affordable perspective which has already been considered in the past could be the implementation of a baseline screening of the prothrombotic state to provide health care professionals with objective data to support the prescription of the more appropriate contraceptive method. While this strategy was judged too expensive due to limited laboratory solutions, the endogenous thrombin potential-based APC resistance assay could now represent an interesting alternative.

The recombinant plant Bauhinia bauhinioides elastase inhibitor reduces rat thrombus without alterations in hemostatic parameters

The anti-inflammatory effects of the plant protease inhibitor BbCI (Bauhinia bauhinioides cruzipain inhibitor), which blocks elastase, cathepsin G, and L, and proteinase 3 has been demonstrated. Here, we investigated the recombinant rBbCI-His(6) (containing a histidine tail) in an experimental venous thrombosis model of vena cava (VC) ligature in rats, comparing to heparin. We evaluate the effects of the inhibitors (native or recombinant) or heparin on the activated partial thromboplastin time (aPTT) and prothrombin time (PT) in human and rat plasmas. The rats undergoing treatment received a saline solution or increasing concentrations of rBbCI-His(6), heparin, or a mixture of both. After 4 h of ligature VC, thrombus, if present was removed and weighed. aPTT, PT, and cytokines were measured in blood collected by cardiac puncture. aPTT, PT, and bleeding time (BT) were also measured at the time of VC (vena cava) ligature. rBbCI-His(6) (0.45 or 1.40 mg/kg) does not alter aPTT, PT or BT. No differences in coagulation parameters were detected in rBbCI-His(6) treated rats at the time of VC ligature or when the thrombus was removed. There was a significant decrease in the weight of thrombus in the animals of the groups treated with the rBbCI-His(6) (1.40 mg/kg), with the rBbCI-His(6) mixture (1.40 mg/kg) + heparin (50 IU/kg) and heparin (100 IU/kg) in relation to control group (saline). The growth-related oncogene/keratinocyte chemoattractant (GRO/KC) serum levels in rats treated with rBbCI-His(6) (1.40 mg/kg) or heparin (200 IU/kg) were reduced. In the experimental model used, rBbCI-His(6) alone had an antithrombotic effect, not altering blood clotting or bleeding time.

Venous Thromboembolism: Genetics and Thrombophilias

Venous thromboembolism (VTE) is a major cause of morbidity and mortality throughout the world. Up to one half of patients who present with VTE will have an underlying thrombophilic defect. This knowledge has led to a widespread practice of testing for such defects in patients who develop VTE. However, identifying a hereditary thrombophilia by itself does not necessarily change outcomes or dictate therapy. Furthermore, family history of VTE by itself can increase an asymptomatic person's VTE risk several-fold, independent of detecting a known inherited thrombophilia. In this article, we will describe the current validated hereditary thrombophilias including their history, prevalence, and association with VTE. With a focus on evaluating both risks and benefits of testing, we will also explore the controversies of why, who, and when to test as well as discuss contemporary societal guidelines. Lastly, we will share how these tests have been integrated into clinical practice and how to best utilize them in the future.

Thrombophilia screening revisited: an issue of personalized medicine

Clinical thrombophilia is the consequence of multiple gene and/or environment interactions. Thrombophilia screening requires a targeted patient with specific indication, in which a finding would have implications. Carrying out a thrombophilia examination in the physician's practice is often a cause of uncertainty and concern. The concerns begin in choosing the right patient to be examined, are associated with the time of investigation, with the choice of analysis, the test-material and with the correct interpretation of the results. Difficulties, which can influence the results, can occur with both organization and blood sampling. As common for any analysis, pre-analytical, analytical and post-analytical factors should be considered, as well as the possibility of false positive or false negative results. Finally, recommendation of correct therapeutic and prophylactic measures for the patient and his relatives is an additional focus. In this article we want to provide-on the basis of the evidence and personal experience-the theory of thrombophilia-investigation, the indications for testing, as well as practical recommendations for treatment options.

Implications of venous thromboembolism GWAS reported genetic makeup in the clinical outcome of ovarian cancer patients

Ovarian cancer (OC) represents the most lethal gynaecological neoplasia. Conversely, venous thromboembolism (VTE) and OC are intricately connected, with many haemostatic components favouring OC progression. In light of this bilateral relationship, genome-wide association studies (GWAS) have reported several single-nucleotide polymorphisms (SNPs) associated with VTE risk that could be used as predictors of OC clinical outcome for better therapeutic management strategies. Thus, the present study aimed to analyse the impact of VTE GWAS-identified SNPs on the clinical outcome of 336 epithelial ovarian cancer (EOC) patients. Polymorphism genotyping was performed using the TaqMan^® Allelic Discrimination methodology. Carriers with the ZFPM2 rs4734879 G allele presented a significantly higher 5-year OS, 10-year OS and disease-free survival (DFS) compared to AA genotype patients with FIGO I/II stages (P = 0.009, P = 0.001 and P = 0.003, respectively). Regarding SLC19A2 rs2038024 polymorphism, carriers with the CC genotype presented a significantly lower 5-year OS, 10-year OS and DFS compared to A allele carriers in the same FIGO subgroup (P < 0.001, P = 0.004 and P = 0.005, respectively). As for CNTN6 rs6764623 polymorphism, carriers with the CC genotype presented a significantly lower 5-year OS compared to A allele carriers with FIGO I/II stages (P = 0.015). As for OTUD7A rs7164569, F11 rs4253417 and PROCR rs10747514, no significant impact on EOC patients' survival was observed. However, future studies are required to validate these results and uncover the biological mechanisms underlying our results.

Genetic association study of fatal pulmonary embolism

Pulmonary embolism (PE) is a complex multi-factorial disease and represents one manifestation of venous thromboembolism (VTE). Most commonly PE constitutes a complication of VTE’s other clinical presentation deep vein thrombosis (DVT). The majority of studies concerning risk factors do not distinguish between PE and DVT. The risk factors are often estimated to be alike, but the prevalence and the risk associated with the major genetic factor Factor V Leiden differ between the two disease states. We have investigated the association of 22 SNPs with PE in 185 PE case and 375 healthy control subjects. At p = 0.05, eight SNPs presented with nominally significant evidence of association (EOA), although no significantly different genotype distributions remained between cases and controls after Bonferroni correction. Three of these variants (rs1800790, rs3813948, rs6025) showed EOA in the main analysis, and five variants (rs169713, rs1801131, rs4524, rs5985 and rs8176592) demonstrated EOAs in subgroups. Genomic variation modulating Factor V, Factor XIII, Beta fibrinogen (FGB), TFPI or HIVEP1 should be worth to be followed in subsequent studies. The findings of this study support the view that PE represents a complex disease with many factors contributing relatively small effects. Larger sample sizes will be required to reliably detect these small effects.

The Silence Speaks, but We Do Not Listen: Synonymous c.1824C>T Gene Variant in the Last Exon of the Prothrombin Gene as a New Prothrombotic Risk Factor

BACKGROUND

Thrombosis is a major global disease burden with almost 60% of cases related to underlying heredity and most cases still idiopathic. Synonymous single nucleotide polymorphisms (sSNPs) are considered silent and phenotypically neutral. Our previous study revealed a novel synonymous FII c.1824C>T variant as a potential risk factor for pregnancy loss, but it has not yet been associated with thrombotic diseases.

METHODS

To determine the frequency of the FII c.1824C>T variant we have sequenced patients' DNA. Prothrombin RNA expression was measured by quantitative PCR. Functional analyses included routine hemostasis tests, western blotting and ELISA to determine prothrombin levels in plasma, and global hemostasis assays for thrombin and fibrin generation in carriers of the FII c.1824C>T variant. Scanning electron microscopy was used to examine the structure of fibrin clots.

RESULTS

Frequency of the FII c.1824C>T variant was significantly increased in patients with venous thromboembolism and cerebrovascular insult. Examination in vitro demonstrated increased expression of prothrombin mRNA in FII c.1824T transfected cells. Our ex vivo study of FII c.1824C>T carriers showed that the presence of this variant was associated with hyperprothrombinemia, hypofibrinolysis, and formation of densely packed fibrin clots resistant to fibrinolysis.

CONCLUSION

Our data indicate that FII c.1824C>T, although a synonymous variant, leads to the development of a prothrombotic phenotype and could represent a new prothrombotic risk factor. As a silent variant, FII c.1824C>T would probably be overlooked during genetic screening, and our results show that it could not be detected in routine laboratory tests.

Prothrombotic genotypes and risk of major bleeding in patients with incident venous thromboembolism

BACKGROUND

Genotypes associated with venous thromboembolism (VTE) may protect against bleeding due to a hypercoagulable state. Whether the risk of major bleeding is reduced in parallel with an increasing number of prothrombotic genotypes during anticoagulant treatment in VTE remains unknown.

OBJECTIVES

To investigate the association between multiple prothrombotic genotypes and risk of major bleeding in patients with VTE.

METHODS

Patients with incident VTE (n = 676) derived from the Tromsø Study were genotyped for rs6025 (F5), rs1799963 (F2), rs8176719 (ABO), rs2066865 (FGG) and rs2036914 (F11) single nucleotide polymorphisms (SNPs). Major bleeding events were recorded during the first year after VTE according to the International Society on Thrombosis and Haemostasis criteria. Cox-regression was used to calculate hazard ratios with 95% confidence intervals (CIs) for major bleeding adjusted for age, sex and duration of anticoagulation according to individual prothrombotic SNPs and categories of risk alleles (5-SNP score; 0-1, 2, 3 and ≥4).

RESULTS

In total, 50 patients experienced major bleeding (incidence rate: 9.5/100 person-years, 95% CI 7.2-12.5). The individual SNPs and number of risk alleles were not associated with major bleeding risk. The hazard ratios for major bleeding per category increase of genetic risk score were 1.0 (95% CI 0.8-1.3) for the total study population and 1.1 (95% CI 0.8-1.5) when patients with active cancer were excluded. Analyses restricted to the first 3 months after VTE yielded similar results.

CONCLUSION

Our findings suggest that an increasing number of prothrombotic risk alleles is not protective against major bleeding in VTE patients during anticoagulation.

Myocardial infarction, prothrombotic genotypes, and venous thrombosis risk: The Tromsø Study

BACKGROUND

The risk of venous thromboembolism (VTE) is increased after a myocardial infarction (MI). Some prothrombotic genotypes associated with VTE have also been associated with risk of MI. Whether prothrombotic single-nucleotide polymorphisms (SNPs) further increase the risk of VTE in MI patients is scarcely investigated.

AIM

To study the combined effect of MI and prothrombotic SNPs on the risk of VTE.

METHODS

Cases with incident VTE (n = 641) and a randomly sampled subcohort weighted for age (n = 1761) were identified from the 4 to 6 surveys of the Tromsø Study (1994-2012). DNA was genotyped for rs8176719 (ABO), rs6025 (F5), rs1799963 (F2), rs2066865 (FGG), and rs2036914 (F11). Hazard ratios (HRs) for VTE with 95% confidence intervals (CIs) were estimated by categories of risk alleles and MI status.

RESULTS

Patients with MI had a 1.4-fold increased risk of VTE, and adjustments for the 5 SNPs, either alone or in combination, did not affect this relationship (adjusted HR, 1.52; 95% CI, 1.12-2.07). In subjects without MI, an increased risk of VTE was observed for each of the individual SNPs (≥1 vs. 0 risk alleles), and the risk increased linearly with increasing number of risk alleles in the 5-SNP score. The combination of MI and prothrombotic genotypes, either as individual SNPs or in the 5-SNP score, did not result in an excess risk of VTE.

CONCLUSION

The relationship between MI and VTE was not explained by these 5 prothrombotic genotypes. Prothrombotic genotypes did not yield an excess risk of VTE in patients with MI.

Thrombophilic risk factors are laterally associated with Apolipoprotein E gene polymorphisms in deep vein thrombosis patients: An Indian study

INTRODUCTION

Deep vein thrombosis is a multifactorial disease with many acquired and genetic risk factors. Polymorphism in the APOE gene is an upcoming potential pathogenic factor whose role is unclear in deep vein thrombosis.

METHODS

An equal number of deep vein thrombosis cases and controls (N = 100, each) were investigated for APOE gene polymorphisms along with known acquired and hereditable thrombophilic risk factors. APOE genotyping was done by polymerase chain reaction.

RESULTS

The ε3/ε4 and ε2/ε3 APOE genotypes were commoner in deep vein thrombosis cases than controls but not statistically significant ( ε3/ε4 → 18% versus 11%, OR = 1.776, CI = 0.792-3.984, p = 0.16; ε2/ε3 →10% versus 9%, OR = 1.123, CI = 0.436-2.895, p = 0.809). However, the following risk factors were found to be laterally associated with APOE genotypes in cases of deep vein thrombosis: pregnancy with ε2/ε3 genotype positivity (N = 29; p = 0.019), recurrent pregnancy loss with ε3/ε3 genotype (N = 29; p = 0.016), normal antithrombin levels with ε3/ε3 genotype (N = 62; p = 0.03) and non-O blood group with ε3/ε4 genotype (N = 100; p = 0.023).

CONCLUSION

APOE genotypes have shown only a modest association with deep vein thrombosis and were not statistically significant. A lateral association of these genotypes with thrombophilic risk factors was observed which may be investigated further for the possible pathogenetic mechanisms and their therapeutic implications.

Association of the CYP4V2 polymorphism rs13146272 with venous thromboembolism in a Chinese population

Genome-wide association studies have identified the CYP4V2 polymorphism (rs13146272) as a risk factor associated with venous thromboembolism (VTE). However, due to the small sample size and variance in genetic analysis models, the relationship between VTE and rs13146272 remains unclear. Here, we performed a case-control study to analyse the associations between rs13146272 and VTE in a Chinese population and to compare the differences among various ethnicities. In this study, 226 VTE patients and 205 healthy controls were recruited, and the allele frequency of variant rs13146272 was analysed by a MassARRAY SNP genotyping assay. In addition, 9 case-control cohorts from 5 studies involving 6667 VTE-affected individuals and 8716 control subjects were included in this meta-analysis. Pooled ORs and 95% CIs were calculated to assess the association between rs13146272 and VTE by using different genetic models. Our case-control study results showed that there was no significant association between VTE and rs13146272 under the additive model (OR = 0.92, 95% CIs: 0.70-1.21, p = 0.55) in this Chinese population. However, the results of the meta-analysis performed by merging all cohorts showed that rs13146272 was significantly associated with VTE under the additive model, recessive model and dominant model. In the additive and recessive models, the association reached the threshold for genome-wide significance (p < 5.0e^-08). In conclusion, our pooled systematic study results indicated that individuals with the A allele had a higher risk of developing VTE than those with the C allele of the rs13146272 variant, but the risk was inconsistent among different ethnicities. Further validation of this association with larger sample sizes and multiple ethnicities is warranted.

Epidemiology and pathophysiology of venous thromboembolism: similarities with atherothrombosis and the role of inflammation

Venous thromboembolism (VTE) is a multifactorial disease. Major provoking factors (e. g. surgery, cancer, major trauma, and immobilisation) are identified in 50–60 % of patients, while the remaining cases are classified as unprovoked. However, minor predisposing conditions may be detectable in these patients, possibly concurring to the pathophysiology of the disease, especially when co-existing. In recent years, the role of chronic inflammatory disorders, infectious diseases and traditional cardiovascular risk factors has been extensively investigated. Inflammation, with its underlying prothrombotic state, could be the potential link between these risk factors, as well as the explanation for the reported association between arterial and venous thromboembolic events.

Thrombophilia Screening: Universal, Selected, or Neither?

The utility of thrombophilia testing in clinical practice is still a matter of debate because studies have not shown a benefit in the reduction of recurrent venous thromboembolism (VTE) risk in patients with thrombosis, despite the clearly higher VTE risk for first thrombosis. Screening for thrombophilia is indicated in selected patients. Particularly in selected young patients, especially women of childbearing age, the knowledge of the genetic thrombophilic defect may help in specific situations to decrease the risk of VTE events. Avoidance of modifiable risk factors and/or prophylactic thromboembolic procedures may be evaluated in selected patients. A comprehensive workup including personal and familial history, clinical examination, and laboratory test results including hereditary thrombophilia remains helpful in assessing the cumulative risk and the management of this group of selected patients.

Environmental and Genetic Risk Factors Associated with Venous Thromboembolism

Venous thromboembolism (VTE) includes deep vein thrombosis and pulmonary embolism, and a combination of environmental and genetic risk factors contributes to VTE risk. Within environmental risk factors, some are provoking (e.g., cancer, surgery, trauma or fracture, immobilization, pregnancy and the postpartum period, long-distance travel, hospitalization, catheterization, and acute infection) and others are nonprovoking (e.g., age, sex, race/ethnicity, body mass index and obesity, oral contraceptive or hormone therapy use, corticosteroid use, statin use, diet, physical activity, sedentary time, and air pollution). Additionally, VTE has a strong genetic basis, with approximately 50 to 60% of the variance in VTE incidence attributed to genetic effects. Some genetic susceptibility variants that contribute to risk have been identified in candidate genes, mostly related to the clotting system and responsible for inherited hypercoagulable states (e.g., factor V Leiden, prothrombin, fibrinogen gamma, or blood group non-O). Other susceptibility single-nucleotide polymorphisms have been identified from genome-wide association studies, such as the two new loci in TSPAN15 (rs78707713) and SCL44A2 (rs2288904) genes. Risk factors are not always associated with VTE in isolation; however, and an understanding of how environmental and genetic factors interact may provide insight into the pathophysiology of VTE, possibly identifying opportunities for targeted prevention and treatment.

Air pollution and venous thrombosis: a meta-analysis

Exposure to air pollution has been linked to cardiovascular and respiratory disorders. However, the effect of air pollution on venous thrombotic disorders is uncertain. We performed a meta-analysis to assess the association between air pollution and venous thrombosis. PubMed, Embase, EBM Reviews, Healthstar, Global Health, Nursing Database, and Web of Science were searched for citations on air pollutants (carbon monoxide, sulfur dioxide, nitrogen dioxide, ozone, and particulate matters) and venous thrombosis. Using a random-effects model, overall risk estimates were derived for each increment of 10 μg/m³ of pollutant concentration. Of the 485 in-depth reviewed studies, 8 citations, involving approximately 700,000 events, fulfilled the inclusion criteria. All the main air pollutants analyzed were not associated with an increased risk of venous thrombosis (OR = 1.005, 95% CI = 0.998–1.012 for PM_2.5; OR = 0.995, 95% CI = 0.984–1.007 for PM₁₀; OR = 1.006, 95% CI = 0.994–1.019 for NO₂). Based on exposure period and thrombosis location, additional subgroup analyses provided results comparable with those of the overall analyses. There was no evidence of publication bias. Therefore, this meta analysis does not suggest the possible role of air pollution as risk factor for venous thrombosis in general population.

Joint effects of cancer and variants in the factor 5 gene on the risk of venous thromboembolism

Venous thromboembolism occurs frequently in cancer patients. Two variants in the factor 5 gene (F5), rs6025 encoding for the factor V Leiden mutation R506Q, and rs4524 encoding K858R, have been found to be associated with venous thromboembolism. We assessed the joint effect of active cancer and these two F5 variants on venous thromboembolism risk in a case-cohort study. Cases with a first venous thromboembolism (n=609) and a randomly selected age-weighted cohort (n=1,691) were sampled from the general population in Tromsø, Norway. Venous thromboembolism was classified as cancer-related if it occurred in the period 6 months before to 2 years after a diagnosis of cancer. Active cancer was associated with an 8.9-fold higher risk of venous thromboembolism (95% CI 7.2-10.9). The risk of cancer-related venous thromboembolism was 16.7-fold (95% CI 9.9-28.0) higher in subjects heterozygous for rs6025 compared with non-carriers of this variant without active cancer. In subjects with active cancer the risk of venous thromboembolism was 15.9-fold higher (95% CI 9.1-27.9) in those with one risk allele at rs4524, and 21.1-fold (95% CI 12.4-35.8) higher in those with two risk alleles compared with non-carriers without active cancer. A synergistic interaction was observed between active cancer and factor V Leiden (relative excess risk due to interaction 7.0; 95% CI 0.5-14.4) and rs4524 (relative excess risk due to interaction 15.0; 95% CI 7.5-29.2). The incidence of venous thromboembolism during the initial 6 months following a diagnosis of cancer was particularly high in subjects with risk alleles at these loci. This implies that the combination of cancer and F5 variants synergistically increases venous thromboembolism risk.

Elevated risk of venous thromboembolic events in patients with inflammatory myopathies

Venous thromboembolism (VTE) is a multifactorial disease manifesting as either deep vein thrombosis or pulmonary embolism. Its prevalence makes VTE a significant issue for both the individual – as a negative factor influencing the quality of life and prognosis – and the society due to economic burden. VTE is the third most common vascular disorder in Western countries, after myocardial infarction and stroke, making it a major cause of in-hospital mortality, responsible for 5%–10% of hospital deaths. Despite many studies conducted, only 50%–60% provoking factors have been identified, while the remaining 40%–50% have been classified as idiopathic or unprovoked. Chronic inflammatory disorders, with their underlying prothrombotic state, reveal an increased risk of VTE (six to eight times) compared with the general population. Among the inflammatory disorders, we can identify inflammatory myopathies – a group of rare, chronic diseases featuring weakness and inflammation of muscles with periods of exacerbation and remission; their main classes are polymyositis and dermatomyositis. The objective of this review is to emphasize the need of VTE prophylaxis in individuals with inflammatory myopathies in order to reduce morbidity and mortality rates among those patients and improve their quality of life and prognosis.

Endothelial protein C receptor gene 6936A/G single-nucleotide polymorphism as a possible biomarker of thrombotic risk in acute myeloid leukemia

Protein C (PC) is a natural anticoagulant, which interacts with the endothelial PC receptor (EPCR). EPCR single-nucleotide polymorphism (SNP) 6936A/G results in high levels of a free soluble form of EPCR (sEPCR) and may affect the risk of coagulation. The objective of this study was to assess whether the 6936A/G SNP of the EPCR gene is involved in the procoagulant activity displayed by hematological malignancies. EPCR 6936A/G polymorphism analysis was performed in 205 patients with hematological malignancies and in 63 healthy controls. All the subjects were genotyped for the EPCR 6936A/G SNP (AA, AG and GG genotypes). The 6936A/G polymorphism distribution was similar between healthy donors and patients. The association between EPCR 6936A/G SNP and thrombosis was investigated in 110 patients. The disease-wise break-up revealed that 55 of the patients suffered from acute myeloid leukemia (AML). In AML patients, the incidence of thrombosis was 28.3% and significantly higher in the 6936AG compared with that in the 6936AA genotype (50 vs. 22%, respectively). In conclusion, this study revealed a significant association of the 6936AG genotype of EPCR with thrombotic events in AML. Therefore, the presence of the 6936AG genotype in AML patients may be considered as a risk indicator of thrombosis.

Epidemiology of venous thromboembolism

Thrombosis can affect any venous circulation. Venous thromboembolism (VTE) includes deep-vein thrombosis of the leg or pelvis, and its complication, pulmonary embolism. VTE is a fairly common disease, particularly in older age, and is associated with reduced survival, substantial health-care costs, and a high rate of recurrence. VTE is a complex (multifactorial) disease, involving interactions between acquired or inherited predispositions to thrombosis and various risk factors. Major risk factors for incident VTE include hospitalization for surgery or acute illness, active cancer, neurological disease with leg paresis, nursing-home confinement, trauma or fracture, superficial vein thrombosis, and-in women-pregnancy and puerperium, oral contraception, and hormone therapy. Although independent risk factors for incident VTE and predictors of VTE recurrence have been identified, and effective primary and secondary prophylaxis is available, the occurrence of VTE seems to be fairly constant, or even increasing.

Meta-analysis of 65,734 individuals identifies TSPAN15 and SLC44A2 as two susceptibility loci for venous thromboembolism

Venous thromboembolism (VTE), the third leading cause of cardiovascular mortality, is a complex thrombotic disorder with environmental and genetic determinants. Although several genetic variants have been found associated with VTE, they explain a minor proportion of VTE risk in cases. We undertook a meta-analysis of genome-wide association studies (GWASs) to identify additional VTE susceptibility genes. Twelve GWASs totaling 7,507 VTE case subjects and 52,632 control subjects formed our discovery stage where 6,751,884 SNPs were tested for association with VTE. Nine loci reached the genome-wide significance level of 5 × 10(-8) including six already known to associate with VTE (ABO, F2, F5, F11, FGG, and PROCR) and three unsuspected loci. SNPs mapping to these latter were selected for replication in three independent case-control studies totaling 3,009 VTE-affected individuals and 2,586 control subjects. This strategy led to the identification and replication of two VTE-associated loci, TSPAN15 and SLC44A2, with lead risk alleles associated with odds ratio for disease of 1.31 (p = 1.67 × 10(-16)) and 1.21 (p = 2.75 × 10(-15)), respectively. The lead SNP at the TSPAN15 locus is the intronic rs78707713 and the lead SLC44A2 SNP is the non-synonymous rs2288904 previously shown to associate with transfusion-related acute lung injury. We further showed that these two variants did not associate with known hemostatic plasma markers. TSPAN15 and SLC44A2 do not belong to conventional pathways for thrombosis and have not been associated to other cardiovascular diseases nor related quantitative biomarkers. Our findings uncovered unexpected actors of VTE etiology and pave the way for novel mechanistic concepts of VTE pathophysiology.

Predicting venous thrombosis in women using a combination of genetic markers and clinical risk factors

BACKGROUND

Family history of venous thromboembolism (VTE) has been suggested to be more useful in risk assessment than thrombophilia testing.

OBJECTIVES

We investigated established genetic susceptibility variants for association with VTE and evaluated a genetic risk score in isolation and combined with known trigger factors, including family history of VTE.

PATIENTS/METHOD

A total of 18 single nucleotide polymorphisms (SNPs) selected from the literature were genotyped in 2835 women participating in a Swedish nationwide case-control study (the ThromboEmbolism Hormone Study [TEHS]). Association with VTE was assessed by odds ratios (ORs) with 95% confidence interval (CI) using logistic regression. Clinical and genetic predictors that contributed significantly to the fit of the logistic regression model were included in the prediction models. SNP-SNP interactions were investigated and incorporated into the models if found significant. Risk scores were evaluated by calculating the area under the receiver-operating characteristics curve (AUC).

RESULTS

Seven SNPs (F5 rs6025, F2 rs1799963, ABO rs514659, FGG rs2066865, F11 rs2289252, PROC rs1799810 and KNG1 rs710446) with four SNP-SNP interactions contributed to the genetic risk score for VTE, with an AUC of 0.66 (95% CI, 0.64-0.68). After adding clinical risk factors, which included family history of VTE, the AUC reached 0.84 (95% CI, 0.82-0.85). The goodness of fit of the genetic and combined scores improved when significant SNP-SNP interaction terms were included.

CONCLUSION

Prediction of VTE in high-risk individuals was more accurate when a combination of clinical and genetic predictors with SNP-SNP interactions was included in a risk score.

Hormones and venous thromboembolism among postmenopausal women

Abstract Venous thromboembolism (VTE) is a common and potentially fatal disease in postmenopausal women. VTE has emerged as the most prevalent adverse effect of oral estrogens in 50-60-year-old women. Obesity and VTE history can be easily used to identify women at high risk but genetic screening is not cost-effective. Based on consistent biological and epidemiological findings, transdermal estrogen is the safest option with respect to VTE, especially in women at high risk. There is strong evidence that VTE risk is greater in women using medroxyprogesterone acetate compared with those receiving other progestins. Based on observational data, progesterone appears safe with respect to VTE. More research and action are needed to avert the hepatic first-pass effect of oral estrogens and to increase awareness of hormone-related VTE. Improving individual risk stratification and a personalized approach to hormone therapy are major challenges for future work.

A genomewide study of body mass index and its genetic correlation with thromboembolic risk. Results from the GAIT project

Thrombosis and obesity are complex epidemiologically associated diseases. The mechanism of this association is not yet understood. It was the objective of this study to identify genetic components of body mass index (BMI) and their possible role in the risk of thromboembolic disease. With the self-reported BMI of 397 individuals from 21 extended families enrolled in the GAIT (Genetic Analysis of Idiopathic Thrombophilia) Project, we estimated the heritability of BMI and the genetic correlation with the risk of thrombosis. Subjects were genotyped for an autosomal genome-wide scan with 363 highly-informative DNA markers. Univariate and bivariate multipoint linkage analyses were performed. The heritability for BMI was 0.31 (p=2.9×10⁻⁵). Thromboembolic disease (including venous and arterial) and BMI had a significant genetic correlation (ρG=0.54, p=0.005). Two linkage signals for BMI were obtained, one at 13q34 (LOD=3.36, p=0.0004) and other at 2q34, highly suggestive of linkage (LOD=1.95). Bivariate linkage analysis with BMI and thrombosis risk also showed a significant signal at 13q34 (LOD=3), indicating that this locus influences at the same time normal variation in the BMI phenotype as well as susceptibility to thrombosis. In conclusion, BMI and thrombosis are genetically correlated. The locus 13q34, which showed pleiotropy with both phenotypes, contains two candidate genes, which may explain our linkage pleiotropic signal and deserve further investigation as possible risk factors for obesity and thrombosis.