Factor XIII Val34Leu polymorphism, factor XIII antigen levels and activity and the risk of deep venous thrombosis

Cancer-associated thrombosis: the role of inherited thrombophilia

Cancer-associated thrombosis (CAT) is a common complication and a major cause of morbidity and mortality in patients with active cancers. CAT is common in various malignancies, particularly pancreatic, ovarian, gastric, colorectal, and hematologic cancers. In fact, CAT is a complicated multifactorial complication that may be influenced by the type of cancer as well as by the genetic background and inheritance of thrombophilic variants and elevated concentrations of coagulation factors. Several studies have shown the prominent role of inherited thrombophilias, such as prothrombin 20210, factor V Leiden, factor XIII Val34Leu, MTHFR C677T, in the occurrence of CAT, while others have found no correlation between them and CAT. In the present review, we have attempted to investigate the possible role of inherited thrombophilia in the occurrence of CAT.

Genomic science of risk prediction for venous thromboembolic disease: convenient clarification or compounding complexity

Venous thromboembolism (VTE) refers to abnormal blood clots in veins occurring in 1 to 2 per 1000 individuals every year. While anticoagulant treatment can prevent VTE, it increases the risk of bleeding. This emphasizes the importance of identifying individuals with a high risk of VTE and providing prophylactic interventions to these individuals to reduce both VTE and bleeding risks. Current risk assessment of VTE is based on the combination of mainly clinical risk factors. With the identification of an increasing number of genetic variants associated with the risk of VTE, the addition of genetic findings to clinical prediction models can improve risk prediction for VTE. Especially for individuals in high-risk situations, the added value of genetic findings to clinical prediction models may have benefits such as better prophylaxis of VTE and the reduced side effects of bleeding from unnecessary treatment. Nevertheless, the question of whether these models will eventually have clinical utility remains to be proven. Here, we review the current state of knowledge on genetic risk factors for VTE, explore genetic prediction models for VTE, and discuss their clinical implications and challenges.

An Exploratory Study Using Next-Generation Sequencing to Identify Prothrombotic Variants in Patients with Cerebral Vein Thrombosis

Prothrombotic hereditary risk factors for cerebral vein thrombosis (CVT) are of clinical interest to better understand the underlying pathophysiology and stratify patients for the risk of recurrence. This study explores prothrombotic risk factors in CVT patients. An initial screening in patients of the outpatient clinic of the Department of Transfusion Medicine and Hemostaseology of the University Hospital Erlangen, Germany, revealed 183 patients with a history of CVT. An initial screening identified a number of common prothrombic risk factors, including Factor V Leiden (rs6025) and Prothrombin G20210A (rs1799963). All patients without relevant findings (58 individuals) were invited to participate in a subsequent genetic analysis of 55 relevant genes using next-generation sequencing (NGS). Three intron variants (ADAMTS13: rs28446901, FN1: rs56380797, rs35343655) were identified to occur with a significantly higher frequency in the CVT patient cohort compared to the general European population. Furthermore, the combined prevalence of at least two of four potentially prothrombic variants (FGA (rs6050), F13A1 (rs5985), ITGB3 (rs5918), and PROCR (rs867186)) was significantly higher in the CVT subjects. The possible impact of the identified variants on CVT is discussed.

Factor XIII-A Val34Leu and Tyr204Phe variants influence clot kinetics in a cohort of South African type 2 diabetes mellitus patients

Factor XIII, a transglutaminase that plays a crucial role in clot formation, consists of subunits A and B. Single nucleotide polymorphisms in Factor XIII-A have been linked to thrombotic risk. In Type 2 Diabetes mellitus (T2DM), a hypercoagulable state is thought to contribute to the high mortality rate associated with thrombotic diseases. Due to the lack of prevalence data of FXIII-A single nucleotide polymorphisms (SNPs) in T2DM in a South African cohort, this study assessed the prevalence FXIII-A Val34Leu (rs5985) and Tyr204Phe (rs3024477) SNP's and the effect on clot kinetics in T2DM.

MATERIALS AND METHODS

A cohort of T2DM patients (n = 100) and race, age and gender matched healthy controls (n = 101) were recruited following ethical approval. Thromboelastography® (TEG®) was used to assess the viscoelastic properties in platelet poor plasma (PPP) in controls (n = 91) and T2DM patients (n = 91) younger than 50 years old. Genomic DNA was isolated from whole blood using the Quick-DNA™ Miniprep Plus Kit and PCR-RFLP was used to genotype each sample for FXIII-A rs5985 and rs3024477 SNPs.

RESULTS

TEG® analyses indicated a longer R-time (p < 0.0001) and higher TMRTG (p < 0.0001) in PPP of T2DM patients. Control and T2DM genotype distribution conformed to Hardy-Weinberg equilibrium (p > 0.05). There was a higher prevalence of the wildtype genotype of FXIII-A Tyr204Phe (rs3024477) SNP in T2DM (OR = 0.23, 95% CI = 0.12-0.42, p < 0.0001). The 204Phe variant was more frequent in the Caucasians (OR = 0.39, 95% CI = 0.05-0.33, p < 0.0001). The presence of the 204Phe variant in T2DM affected TMRTG (p = 0.0207). The variant affected R time (p = 0.0432) and TMRTG (p = 0.0209 and p = 0.0207) in controls and T2DM, respectively.

CONCLUSION

An inverse association with T2DM and FXIII-A Tyr204Phe was found. A hypo coagulable PPP clot profile was observed in T2DM. A shorter reaction time was observed and but faster rate at which the clot reached maximum strength in both controls and T2DM in the presence of the 204Phe variant.

Targeted proteomics for evaluating risk of venous thrombosis following traumatic lower-leg injury or knee arthroscopy

INTRODUCTION

Patients with lower-leg cast immobilization and patients undergoing knee arthroscopy have an increased risk of venous thrombosis (VT). Guidelines are ambiguous about thromboprophylaxis use, and individual risk factors for developing VT are often ignored. To assist in VT risk stratification and guide thromboprophylaxis use, various prediction models have been developed. These models depend largely on clinical factors and provide reasonably good C-statistics of around 70%. We explored using protein levels in blood plasma measured by multiplexed quantitative targeted proteomics to predict VT. Our aim was to assess whether a VT risk prediction model based on absolute plasma protein quantification is possible.

METHODS

We used internal standards to quantify proteins in less than 10 μl plasma. We measured 270 proteins in samples from patients scheduled for knee arthroscopy or with lower-leg cast immobilization. The two prospective POT-(K)CAST trails allow complementary views of VT signature in blood, namely pre and post trauma, respectively. From approximately 3000 patients, 31 patients developed VT who were included and matched with double the number of controls.

RESULTS

Top discriminating proteins between cases and controls included APOC3, APOC4, APOC2, ATRN, F13B, and F2 in knee arthroscopy patients and APOE, SERPINF2, B2M, F13B, AFM, and C1QC in patients with lower-leg cast. A logistic regression model with cross-validation resulted in C-statistics of 88.1% (95% CI: 85.7-90.6%) and 79.6% (95% CI: 77.2-82.0%) for knee arthroscopy and cast immobilization groups respectively.

CONCLUSIONS

Promising C-statistics merit further exploration of the value of proteomic tests for predicting VT risk upon additional validation.

Low FXIII activity levels in intensive care unit hospitalized COVID-19 patients

Background

COVID-19 infection is associated with a hypercoagulable state. Severe COVID-19 patients present with high plasma fibrinogen levels, continuous deposition of fibrin and the presence of microthrombi in their lungs, accompanied by significant fibrinolysis, resulting in high D-dimer levels. Due to the role of FXIII in fibrin crosslinking and clot stabilization, we analyzed its activity levels and dynamics in COVID-19 patients hospitalized in the intensive care unit (ICU).

Methods

FXIII levels were measured in thirty four COVID-19 patients hospitalized in the ICU and in fourteen non-severe COVID-19 patients. FVIII levels were measured for comparison. Laboratory data and clinical variables were recorded.

Results

The average FXIII activity level in 34 ICU hospitalized COVID-19 patients was 69.9±33 %, significantly lower compared to an average of 120±20.9 % FXIII activity in 14 non-severe COVID-19 patients. FXIII activity levels were below the low normal value (< 79 % FXIII activity) in 74 % of the ICU hospitalized COVID-19 patients. In contrast, high FVIII activity was measured among all severe COVID-19 patients. Consecutive measurements, performed in fourteen ICU hospitalized COVID-19 patients, pointed to a significant decrease in FXIII activity from the average of 85.7±28.2 %, (which is in the normal range), to an average of 68.0±20.4 %, below the low normal range, within 6.4±3.4 days of ICU hospitalization. Liver functions did not differentiate between patients with low and normal FXIII activity. No inhibitor to FXIII activity was found in the plasma of severe COVID-19 patients. Levels of FXIII-A antigen correlated with FXIII activity, and were low in severe COVID-19 patients.

Conclusions

Low FXIII activity levels were found in COVID-19 patients hospitalized in the ICU, with gradual decline during their hospitalization. A mechanism of consumption may account for the low FXIII activity in these patients.

Genetic risk factors for venous thromboembolism among infertile men with Klinefelter syndrome

•

Infertile males with KS have sex-chromosome abnormalities, endocrinal disturbances and other health problems.

•

Hereditary thrombophilia may exacerbate tendency to thrombosis in KS patients.

•

Genotype and allele frequency of thrombophilic gene variants were remarkably high in men with KS.

•

The coexistence of different mutant alleles was evident in infertile KS males.

Background

Klinefelter syndrome (KS) is one of the commonest sex chromosome disorders. Affected males become infertile and highly susceptible to several health problems, including vascular thromboembolism (VTE). The risk of VTE may be exacerbated by an underlying genetically inherited thrombophilia. In this study, we aimed to investigate the genotype and allele frequencies of common gene polymorphisms related to hereditary thrombophilia in infertile males with KS compared to normal, fertile men.

Methods

Eighty-five infertile males with KS and 75 healthy control males were included in this case-control study. Genetic testing was done using an extended thrombophilia gene panel by Multiplex PCR reverse hybridization method.

Results

There was an increased frequency of mutant alleles and heterozygous genotypes of FV Leiden, FV H 1299R, Pro G20210A, MTHFR C677T and PAI-1 4G/5G thrombophilic gene polymorphisms in KS patients compared to the control group. It was shown that 10.7% of KS patients had the A3 haplotype of the EPCR gene in comparison to 5.3% of control patients. The A3/A3 genotype was found only in KS patients (7.1%). Carriers of more than one mutant allele in KS patients exceeded the control (p < 0.001).

Conclusion

A high prevalence of thrombophilic gene polymorphisms and the coexistence of different mutant alleles were evident in infertile KS males. These data highlight the importance of conducting further studies to understand the role of hereditary thrombophilia in predicting venous thrombosis in patients with Klinefelter syndrome.

The factor XIII-A Val34Leu polymorphism decreases whole blood clot mass at high fibrinogen concentrations

BACKGROUND

Factor XIII (FXIII) promotes fibrin crosslinking and red blood cell (RBC) retention in clots. The FXIII-A polymorphism, Val34Leu, is associated with protection against venous thrombosis. This effect is hypothesized to result from fibrinogen concentration-dependent changes in fibrin structure. Effects of the FXIII-A Val34Leu polymorphism in whole blood clots have not been investigated.

AIM

Characterize effects of FXIII-A Val34Leu polymorphism and fibrinogen on whole blood clots.

METHODS

We isolated platelet-poor plasmas from human donors (FXIIIVal/Val , FXIIIVal/Leu , FXIIILeu/Leu ), reconstituted plasmas with platelets and RBCs, and triggered clotting. We assessed contributions of gender, age, clotting times, thrombin generation, FXIII activity, FXIII-A Val34Leu polymorphism, and fibrinogen to clot mass. We also reconstituted FXIII-depleted plasma with platelets, RBCs, and purified FXIIIVal/Val or FXIIILeu/Leu , varied fibrinogen, and characterized effects on clot mass.

RESULTS

Clot mass was associated with age, fibrinogen, prothrombin time, and thrombin generation. Clots reconstituted with plasmas from individuals with FXIII-AVal/Val and FXIII-AVal/Leu did not differ in mass from clots with FXIII-ALeu/Leu . However, clots containing a 34Val allele demonstrated a fibrinogen concentration-dependent increase in mass, whereas clots with homozygous 34Leu did not. In plasmas with high fibrinogen, mass was higher for clots with 34Val alleles compared with clots with homozygous 34Leu. In clots reconstituted with purified FXIII, increasing fibrinogen enhanced clot mass in the presence of 34Val, but decreased mass in the presence of 34Leu.

CONCLUSIONS

FXIII 34Leu mitigates the effect of elevated fibrinogen on whole blood clot mass. The Val34Leu polymorphism may protect against venous thrombosis by reducing clot mass.

Coagulopathy in Type 2 Diabetes Mellitus: Pathological Mechanisms and the Role of Factor XIII-A Single Nucleotide Polymorphisms

The prevalence of type 2 diabetes mellitus (T2DM) has quadrupled within three decades since 1980, affecting 422 million adults in 2016. It remains one of the most common noncommunicable chronic diseases and the underlying risk factor for cardiovascular diseases worldwide. There are different underlying mechanisms that play a role in the development of pathologies associated with the disease such as hyperglycaemia, oxidative stress, obesity, inflammation and hypercoagulation; each of which are interlinked. Hyperglycaemia, oxidative stress and obesity play a huge role in the activation of inflammation and coagulation. Activation of inflammatory pathways increases the production of thrombin which predisposes the development of thrombotic related diseases. One of the factors that contribute to the increase of thrombin is the impairment of the fibrinolysis process due to decreased expression of tissue-plasminogen activator (tPA) by increased levels of plasminogen activator inhibitor-1 (PAI-1). Coagulation factor XIII (FXIII), a transglutaminase that is composed of subunits A and B (FXIII-A2B2), is essential for the last step of fibrin clot formation in the coagulation pathway. Genetic variation of FXIII-A in the form of single nucleotide polymorphisms (SNPs) alters the activity of FXIII, altering clot properties which influence disease outcomes. This review discusses the link between underlying mechanisms of T2DM, well known FXIII-A variants and coagulation.

Factor XIII levels and factor XIII B subunit polymorphisms in patients with venous thromboembolism

BACKGROUND

The association of plasma factor XIII (FXIII) level with venous thromboembolism (VTE) is still controversial and the effect of sex and FXIII B subunit (FXIII-B) polymorphisms in this respect have not been explored.

OBJECTIVES

1/ To determine FXIII activity and antigen levels in patients with a history of VTE and how they are influenced by sex and FXIII-B polymorphisms. 2/ To explore the association of FXIII levels and FXIII-B polymorphisms with the risk of VTE.

METHODS

218 VTE patients and equal number of age and sex matched controls were enrolled in the study. FXIII activity was measured by ammonia release assay; FXIII-A₂B₂ and FXIII-B levels were determined by ELISAs. FXIII-B polymorphisms were identified by RT-PCR using melting point analysis.

RESULTS

Adjusted FXIII activity and FXIII-A₂B₂ antigen levels were significantly higher in females with a history of VTE than in the respective controls. FXIII-B levels were significantly lower in male VTE patients than in controls. FXIII-A₂B₂ antigen levels in the upper tertile increased the risk of VTE in females (adjusted OR: 2.52; CI: 1.18-5.38). Elevated FXIII-B antigen level had a protective effect only in males (adjusted OR: 0.19; CI: 0.08-0.46). FXIII-B Intron K c.1952+144 C>G polymorphism significantly lowered FXIII activity, FXIII-A₂B₂ and FXIII-B antigen levels in both groups. FXIII-B polymorphisms did not influence the risk of VTE.

CONCLUSIONS

In VTE patients the changes of FXIII level and their effect on the risk of VTE show considerable sex-specific differences. Intron K polymorphism results in decreased FXIII levels, but does not influence the risk of VTE.

Polymorphisms of the coagulation system and risk of cancer

Hypercoagulability is a frequently finding in patients with cancer, and is associated with an increased risk of venous thrombosis (VT). Cancer-associated VT is associated with poor prognosis and represents the leading non-cancer cause of death among these patients. Conversely, patients experiencing VT are at increased risk of subsequent cancer, suggesting an epidemiological bidirectional link between cancer and hemostasis, and indicating a role of the hemostatic system in cancer development. How the coagulation system relates to cancer etiology at the genetic level is largely unexplored. Data on the association of polymorphisms in genes involved in coagulation with cancer development is important to clarify the role of the coagulation system in cancer pathogenesis. Effects of coagulation-related gene polymorphisms on cancer risk may possibly be translated into novel treatment- and prevention strategies of cancer-associated thrombosis and the cancer itself. This article reviews the current knowledge of the relation between polymorphisms in genes involved in coagulation and cancer risk in solid tumors.

Newly-Recognized Roles of Factor XIII in Thrombosis

Arterial and venous thromboses are major contributors to coagulation-associated morbidity and mortality. Greater understanding of mechanisms leading to thrombus formation and stability is expected to lead to improved treatment strategies. Factor XIII (FXIII) is a transglutaminase found in plasma and platelets. During thrombosis, activated FXIII cross-links fibrin and promotes thrombus stability. Recent studies have provided new information about FXIII activity during coagulation and its effects on clot composition and function. These findings reveal newly-recognized roles for FXIII in thrombosis. Herein, we review published literature on FXIII biology and effects on fibrin structure and stability, epidemiologic data associating FXIII with thrombosis, and evidence from animal models indicating FXIII has an essential role in determining thrombus stability, composition, and size.

Factor XIII A-Subunit V34L Variant Affects Thrombus Cross-Linking in a Murine Model of Thrombosis

OBJECTIVE

Factor XIII (FXIII) cross-links fibrin upon activation by thrombin. Activation involves cleavage at residue 37 by thrombin, releasing an activation peptide. A common polymorphism (valine to leucine variant at residue 34, V34L), located in the activation peptide, has been associated with increased activation rates and paradoxically a protective effect in cardiovascular disease. There is, currently, no data available on the effects of V34L from in vivo models of thrombosis. We examined the effect of FXIII V34L on clot formation and cross-linking in vivo.

APPROACH AND RESULTS

We generated a panel of full-length recombinant human FXIII-A2 variants with amino acid substitutions in the activation peptide to investigate the effect of these variants on activation rate, and we used wild-type, V34L, and alanine to glycine variant at residue 33 variants to study the effects of varying FXIII activation rate on thrombus formation in a murine model of FeCl3 injury. FXIII activation assay showed that residues 29, 30, 33, and 34 play a critical role in thrombin interaction. Full-length recombinant human FXIII-A2 V34L has significant effects on clot formation, structure, and lysis in vitro, using turbidity assay. This variant influenced fibrin cross-linking but not size of the thrombus in vivo.

CONCLUSIONS

Mutations in the activation peptide of full-length recombinant FXIII regulate activation rates by thrombin, and V34L influences in vivo thrombus formation by increased cross-linking of the clot.

VKORC1 -1639 G>A Polymorphism in Romanian Patients With Deep Vein Thrombosis

AIM

The purpose of the research was to study the influence of several genetic factors, especially the -1693 G>A polymorphism of the VKORC1 gene, on the risk of acute unprovoked lower extremity deep vein thrombosis (DVT).

MATERIALS AND METHODS

The study included 127 patients (median age 63 [53.2; 72] years; 61 [48%] women and 66 [52%] men) who were diagnosed with acute lower extremity DVT and 114 controls (median age 62 [53; 73] years; 64 [56.1%] women and 50 [43.9%] men) without DVT. We recorded data regarding the history of DVT and the presence of varicose veins. We determined the genotypes for factor V Leiden (FVL) mutation, prothrombin G20210A mutation, VKORC1 -1639 G>A mutation, and PAI-1 -675 4G/5G polymorphism.

RESULTS AND CONCLUSION

Varicose veins were found in 67 (52.8%) patients and 29 (25.4%) controls (P < .001). FVL was present in 29 (22.8%) patients and 10 (8.8%) controls (P = .005). The VKORC1 (-1693 G>A) GG genotype was found in 42 (33.1%) patients and 41 (36%) controls, the GA genotype in 71 (55.9%) patients and 47 (41.2%) controls, and AA genotype in 14 (11%) patients and 26 (22.8%) controls (P = .020). Multivariate analysis showed that the presence of varicose veins, FVL, and VKORC1 -1639 G>A was independently associated with the risk of DVT. The VKORC1 (-1693 G>A) AA genotype was associated with fewer cases of DVT (odds ratio = 0.435; 95% confidence interval 0.205-0.991; P = .031).

Multilocus genetic risk scores for venous thromboembolism risk assessment

BACKGROUND

Genetics plays an important role in venous thromboembolism (VTE). Factor V Leiden (FVL or rs6025) and prothrombin gene G20210A (PT or rs1799963) are the genetic variants currently tested for VTE risk assessment. We hypothesized that primary VTE risk assessment can be improved by using genetic risk scores with more genetic markers than just FVL-rs6025 and prothrombin gene PT-rs1799963. To this end, we have designed a new genetic risk score called Thrombo inCode (TiC).

METHODS AND RESULTS

TiC was evaluated in terms of discrimination (Δ of the area under the receiver operating characteristic curve) and reclassification (integrated discrimination improvement and net reclassification improvement). This evaluation was performed using 2 age- and sex-matched case-control populations: SANTPAU (248 cases, 249 controls) and the Marseille Thrombosis Association study (MARTHA; 477 cases, 477 controls). TiC was compared with other literature-based genetic risk scores. TiC including F5 rs6025/rs118203906/rs118203905, F2 rs1799963, F12 rs1801020, F13 rs5985, SERPINC1 rs121909548, and SERPINA10 rs2232698 plus the A1 blood group (rs8176719, rs7853989, rs8176743, rs8176750) improved the area under the curve compared with a model based only on F5-rs6025 and F2-rs1799963 in SANTPAU (0.677 versus 0.575, P<0.001) and MARTHA (0.605 versus 0.576, P=0.008). TiC showed good integrated discrimination improvement of 5.49 (P<0.001) for SANTPAU and 0.96 (P=0.045) for MARTHA. Among the genetic risk scores evaluated, the proportion of VTE risk variance explained by TiC was the highest.

CONCLUSIONS

We conclude that TiC greatly improves prediction of VTE risk compared with other genetic risk scores. TiC should improve prevention, diagnosis, and treatment of VTE.

Apolipoprotein E polymorphism is associated with lower extremity deep venous thrombosis: color-flow Doppler ultrasound evaluation

Introduction

Apolipoprotein E (apoE) is a member of apolipoprotein family, and its gene polymorphisms seem to have some impact among patients with cardiovascular disease. However, its role in the lower extremity deep venous thrombosis (LEDVT) has not been well studied. The objective of this study was to investigate the potential association between APOE gene polymorphisms and LEDVT.

Materials and methods

A hospital-based case–control study was conducted in 300 patients with LEDVT by color-flow Doppler ultrasound and 300 age- and gender-matched healthy controls. Polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) assay was applied to assess the APOE gene polymorphisms.

Results

Patients with LEDVT had a significantly higher frequency of APOE E3/E4 genotype [odds ratio (OR) =1.48, 95% confidence interval (CI) = 1.05, 2.10; P = 0.03] than healthy controls. When stratifying by family history of LEDVT, it was found that patients with positive family history of LEDVT had a significantly higher frequency of APOE E3/E4 genotype (OR =1.68, 95% CI = 1.04, 0.95; P = 2.70). When stratifying by smoking status, presence of varicose veins, type 2 diabetes mellitus and any hormone administration before, no significant differences were found in any groups.

Conclusion

Our study suggested that APOE E3/E4 genotype was associated with a higher LEDVT risk. Additional studies are needed to confirm this finding.

Venous thromboembolism: classification, risk factors, diagnosis, and management

Venous thromboembolism (VTE) is categorised as deep venous thrombosis (DVT) and pulmonary embolism (PE). VTE is associated with high morbidity and causes a huge financial burden on patients, hospitals, and governments. Both acquired and hereditary risks factors contribute to VTE. To diagnose VTE, noninvasive cost-effective diagnostic algorithms including clinical probability assessment and D-dimer measurement may be employed followup by compression ultrasonography for suspected DVT patients and multidetector computed tomography angiography for suspected PE patients. There are pharmacological and mechanical interventions to manage and prevent VTE. The pharmacological approaches mainly target pathways in coagulation cascade nonspecifically: conventional anticoagulants or specifically: new generation of anticoagulants. Excess bleeding is one of the major risk factors for pharmacological interventions. Hence, nonpharmacological or mechanical approaches such as inferior vena cava filters, graduated compression stockings, and intermittent pneumatic compression devices in combination with pharmacological interventions or alone may be a good approach to manage VTE.

Molecular mechanisms affecting fibrin structure and stability

Fibrin structure and stability have been linked to many thrombotic diseases, including venous thromboembolism. Analysis of the molecular mechanisms that affect fibrin structure and stability became possible when the crystal structure of fibrinogen was solved. Biochemical studies of natural and recombinant variant fibrinogens have examined the interactions that mediate the conversion of soluble fibrinogen to the insoluble fibrin network. These studies identified intermolecular interactions that control fibrin structure, although some critical events remain ambiguous. Studies show that fibrin structure modulates the enzymatic lysis of the fibrin network, so the molecular mechanisms that control structure also control stability. Studies show that the mechanical stability of the fibrin clot depends on the properties of the fibrin monomer, leading investigators to explore the molecular basis of the monomer's mechanical properties. The work summarized here provides insights that might allow the development of pharmaceuticals and treatments to modulate fibrin structure and stability in vivo and thereby prevent or limit thrombotic disease.

Clotting factor gene polymorphisms and colorectal cancer risk

PURPOSE

Increased coagulation has been associated with cancer onset and progression. Mainly small studies have addressed the association between clotting factor gene polymorphisms and the onset of colorectal cancer. We examined the association between six well-known clotting factor gene polymorphisms and colorectal cancer risk in a large case-control study.

PATIENTS AND METHODS

Factor V Leiden (rs6025), prothrombin G20210A (rs1799963), PAI-1 4G/5G (rs1799889), MTHFR 677C>T (rs1801133), fibrinogen gamma 10034C>T (rs2066865), and factor XIII Val34Leu (rs5985) were genotyped in 1,801 patients with colorectal cancer and 1,853 healthy controls from a large German population-based study. The risk of colorectal cancer associated with gene variants was determined by calculating odds ratios (ORs) and their 95% CIs using logistic regression.

RESULTS

Homozygous carriers of the prothrombotic factor V Leiden polymorphism showed a 5.8-fold increased risk (95% CI, 1.69 to 19.72) for colorectal cancer compared with noncarriers. A 30% reduced risk was found for heterozygous carriers of factor V Leiden (OR = 0.68; 95% CI, 0.52 to 0.90) and prothrombin G20210A (OR = 0.69; 95% CI, 0.49 to 0.96), implying an advantage for slightly increased thrombin generation. Carriers of the antithrombotic factor XIII Val34Leu polymorphism showed a 15% reduced risk of developing colorectal cancer (OR = 0.85; 95% CI, 0.74 to 0.97) compared with noncarriers. Our results did not support an effect of PAI-1 4G/5G, MTHFR 677C>T, and fibrinogen gamma 10034C>T on colorectal cancer risk.

CONCLUSION

Our results support a role of clotting factor polymorphisms and thereby the coagulation system in the risk of colorectal cancer.

Study of 18 functional hemostatic polymorphisms in mucocutaneous bleeding disorders

Hereditary disorders of primary hemostasis, characterized by mucocutaneous bleeding (MCB), are highly prevalent in children. Few cases are clearly monogenic, but the overwhelming majority are classified as mild bleeding disorders, with wide clinical and laboratory heterogeneity suggestive of complex polygenic diseases. In this framework, and by homology with venous thrombosis, some functional polymorphisms affecting the hemostatic system should be considered. We evaluated the role of 18 common hemostatic polymorphisms on the occurrence and severity of MCB in a case-control study including 269 patients and 286 matched controls consecutively recruited. FV Leiden was associated with milder bleeding severity, assessed by a standardized bleeding score (p = 0.013). Multivariate analysis revealed that three additional polymorphisms protected against MCB (F13 Leu34, OR = 0.66; 95% CI, 0.47-0.94; p = 0.024; VKORC1 1173T, OR = 0.59; 95% CI, 0.40-0.87; p = 0.009; and non-O blood group alleles, OR = 0.59; 95% CI, 0.41-0.86; p = 0.006). When combined, these polymorphisms showed an additive protection (OR = 0.24; 95% CI, 0.11-0.52), supporting the polygenic nature of MCB. Our data suggest that some common polymorphisms affecting hemostasis-related genes could protect from bleeding.

The inflammatory response is influenced by FXIII VAL 34 LEU polymorphism in a human LPS model

BACKGROUND

In sepsis, activation of coagulation and inhibition of fibrinolysis lead to microvascular thrombosis. The Val34Leu polymorphism affects the function of FXIII by increasing the rate of FXIII activation by thrombin, which results in an increased and faster rate of fibrin stabilization. Sepsis and multi-organ failure cause disturbance of the normal balance of inflammation and coagulation, one of the most frequent causes of death in ICU patients. Research in polymorphism has shown the possible influence of FXIII in coagulation and inflammation.

METHODS

We analyzed the influence of the common FXIII Val34Leu polymorphism on inflammatory and coagulation parameters in human experimental endotoxinemia. Healthy volunteers (n = 62) received 2 ng endotoxin (LPS) per kg body weight as a bolus infusion over 2 min. We developed a new mutagenic separated PCR assay for determination of the FXIII promoter polymorphism.

RESULTS

FXIII levels were higher for homozygous carriers of the FXIII polymorphism in comparison with wild-type 34 Val/Val and heterozygous 34 Val/Leu. Interestingly, persons homozygous for the FXIII Val34Leu polymorphism had lower monocyte and neutrophil counts throughout the observation period, yet prothrombin fragment 1+2 and D-dimer levels did not differ after LPS challenge.

CONCLUSION

Our findings indicate that the common FXIII Val34Leu polymorphism is associated with differences in monocyte and neutrophil cell counts in response to systemic LPS infusion in humans.

Impaired fibrinolysis as a risk factor for Budd-Chiari syndrome

In Budd-Chiari syndrome (BCS), thrombosis develops in the hepatic veins or inferior vena cava. To study the relationship between hypofibrinolysis and BCS, we measured plasma levels of fibrinolysis proteins in 101 BCS patients and 101 healthy controls and performed a plasma-based clot lysis assay. In BCS patients, plasminogen activator inhibitor 1 (PAI-1) levels were significantly higher than in controls (median, 6.3 vs 1.4 IU/mL, P < .001). Thrombin-activatable fibrinolysis inhibitor and plasmin inhibitor levels were lower than in controls (13.8 vs 16.9 μg/mL and 0.91 vs 1.02 U/L, both P < .001). Median plasma clot lysis time (CLT) was 73.9 minutes in cases and 73.0 minutes in controls (P = .329). A subgroup of cases displayed clearly elevated CLTs. A CLT above the 90th or 95th percentile of controls was associated with an increased risk of BCS, with odds ratios of 2.4 (95% confidence interval, 1.1-5.5) and 3.4 (95% confidence interval, 1.2-9.7), respectively. In controls, only PAI-1 activity was significantly associated with CLT. Analysis of single nucleotide polymorphisms of fibrinolysis proteins revealed no significant differences between cases and controls. This case-control study provides the first evidence that an impaired fibrinolytic potential, at least partially caused by elevated PAI-1 levels, is related to the presence of BCS.

Coagulation factors IX through XIII and the risk of future venous thrombosis: the Longitudinal Investigation of Thromboembolism Etiology

Higher levels of procoagulant factors and factor XII deficiency may be risk factors for first venous thromboembolism (VTE). We studied associations of coagulation factors IX through XIII with risk of future VTE in 2 general population samples. Using a nested case-control study combining the 21 860 participants of the Atherosclerosis Risk in Communities study and the Cardiovascular Health Study, we determined antigenic levels of these coagulation factors in primarily pre-event blood samples from 462 participants who subsequently developed VTE and 1047 participants who remained free of VTE. Only elevated levels of factors IX and XI were associated with increased risk of VTE after adjustment for age, sex, race, and study. For factor IX, the odds ratio (OR) was 1.4 (95% confidence interval [CI], 1.0-2.0) comparing the top to bottom quintile. The OR for factor XI was higher: 2.0 (95% CI, 1.4-2.9). With further adjustment for body mass index and diabetes, only elevated factor XI remained associated with VTE risk: OR 1.8 (95% CI, 1.3-2.7). Associations were similar by study and whether the thrombosis was idiopathic or secondary. Factor XII deficiency was not related to VTE risk. Among these procoagulant factors, only elevated factor XI was a risk factor for VTE.

Genetics of venous thrombosis

Venous thrombosis (deep vein thrombosis, pulmonary embolism) is a common and serious disorder, with genetic and acquired risk factors. The genetic risk factors can be subdivided in to those that are strong, moderate and weak. Strong risk factors are deficiencies of antithrombin, protein C and protein S. Moderately strong are factor V Leiden, prothrombin 20210A, non-O blood group and fibrinogen 10034T. There are many weak genetic risk factors, including fibrinogen, factor XIII and factor XI variants. Even for moderately strong risk factors (relative risks 2-5), the majority of carriers will never develop thrombosis.

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.

Multiplex genotyping for thrombophilia-associated SNPs by universal bead arrays

This chapter describes a method for the multiplex analysis of six biallelic single nucleotide polymorphisms (SNPs) associated with thrombophilia. The method may, however, be adapted for the simultaneous analysis of up to 100 markers (50 biallelic SNPs) in a single reaction. In the method described, the targets of interest are amplified by single-tube multiplex PCR using six primer sets followed by single-tube multiplex allele-specific primer extension using 12 universally tagged genotyping primers. Labeled extension products are sorted using the xTAG universal bead-based array and detected on the Luminex xMAP system. The 12 universal tag sequences used in the assay derive from a set of 100 universal tags which have been designed to be isothermal and have been empirically validated to show that mismatch hybridization events are minimal. The method is suitable for cost-effective high-throughput clinical genotyping applications.

Associations of the beta-fibrinogen Hae III and factor XIII Val34Leu gene variants with venous thrombosis

INTRODUCTION

The factor XIII Val34Leu (100 G-->T) and beta-fibrinogen Hae III (-455 G-->A) gene variants have been associated with reduced risk of venous thrombosis, but not in all studies.

METHODS

We investigated the associations of these polymorphisms with risk of venous thrombosis in a prospective, population-based study of 21,680 men and women aged 45-100 years at enrollment. Factor XIII 100 G/T and beta-fibrinogen -455 G/A were analyzed on stored DNA from 511 thrombosis cases and 1028 control subjects without thrombosis during follow up.

RESULTS

The beta-fibrinogen A allele was present in 24.4% of cases and 32.3% of controls. Compared to GG subjects, the age, race, and sex adjusted odds ratio (OR) of venous thrombosis was 0.77 (95% CI 0.59-0.99) for GA subjects, and 0.60 (95% CI 0.31-1.16) for AA subjects. The adjusted OR of thrombosis associated with factor XIII 100 G/T was 1.01 (95% CI 0.81-1.26) for GT subjects and 0.45 (95% CI 0.44-1.19) for TT subjects, compared to GG. For both genotypes, ORs of thrombosis were similar in whites and non-whites, although there were no non-white fibrinogen AA cases. beta-fibrinogen -455 GA or AA attenuated the thrombosis risk associated with obesity (from 2.14 to 1.25) and factor V Leiden (from 3.89 to 2.36).

CONCLUSIONS

beta-fibrinogen -455 G/A, but not factor XIII 100 G/T, was associated with a lower risk of venous thrombosis in this general population sample. beta-fibrinogen -455 A may attenuate the increased thrombosis risk associated with obesity or factor V Leiden.

Factor XIII gene V34L mutation in the Lebanese population: Another unique feature in this community?

We studied the distribution of the Factor XIII gene V34L polymorphism in a sample of healthy Lebanese individuals to assess its prevalence and compare it with other populations. Factor XIII genotypes were determined using the Cardiovascular Disease (CVD) StripAssay (ViennaLab, Austria), which is based on a Polymerase Chain Reaction-Reverse hybridization technique. DNA from 205 unrelated healthy donors from our HLA database was used. The prevalence of Wild type, heterozygous, and homozygous genotypes was found to be 74.2%, 22.4%, and 3.4% respectively. The sampled Lebanese population showed that the prevalence of V34L carriers (25.8%) was lower than Caucasians in general (44.3%) and, interestingly, with a low allele frequency of 0.14 similar to that in Blacks and South Asians. This first report from Lebanon sheds light on an additional unique genetic feature of this population and will prospectively serve as a baseline statistical data for future investigations of the prevalence of Factor XIII V34L mutation in association with various clinical entities notably cardiovascular diseases.

Mutations in clotting factors and inflammatory bowel disease

BACKGROUND

Patients with Crohn's disease (CD) and ulcerative colitis (UC) have a three- to fourfold greater risk of venous thrombosis compared with the general population. We aimed to determine if patients with CD and UC had a greater likelihood of mutations in genes that increase clotting risk, in a population-based case-control study.

METHODS

Subjects were drawn from the University of Manitoba IBD Research Registry and controls were drawn from Manitoba Health's administrative database. Cases (CD, N = 327; UC, N = 165) and controls (N = 412) underwent venipuncture. DNA was purified from whole blood. Genotypes for wild-type and common mutations that have been associated with venous thrombosis for each of Factor II (prothrombin) (G20210A), Factor V (G1691A:'Leiden'), methylenetetrahydrofolate reductase (MTHFR, C677T), and Factor XIII (val34leu) were assessed.

RESULTS

A total of 1.5% and 6.1% were heterozygous for Factor II and Factor V variants, respectively, without differences among cases and controls. Only one subject was homozygous for Factor V Leiden (and none were homozygous for Factor II mutation). Although some differences were observed among cases and controls in the prevalence of MTHFR C677T (decrease in mutant allele carriership in UC) and FXIII val34leu (increase in double mutant allele carriership in CD), these did not explain an excess risk of thrombosis. Age, sex, or disease phenotypes were not associated with prothrombotic genotypes.

CONCLUSIONS

While there was a slightly greater prevalence of Factor XIII mutation carriership in CD, we did not find that gene mutations for these four common factors could explain the greater risk of venous thrombosis in CD and UC.

An unfavorable combination of factor V Leiden with age, weight, and blood group causes high risk of pregnancy-associated venous thrombosis—a population-based nested case-control study

INTRODUCTION

Hereditary and acquired risk factors increase the risk for thrombosis among pregnant women. Few risk estimates are, however, well established. The aim of the present study was to assess risk for pregnancy-associated venous thrombosis of factor V Leiden (FVL), FII G20210A, FV A4070G, MTHFR C677T, TFPI C536T, PROC T38853G, FXIII V34L, blood group, age, and body mass index (BMI), and their interactions and public health impact.

MATERIALS AND METHODS

Study design is a population-based nested case-control study of 100,000 consecutive pregnancies in Finland. Cases and controls were identified by combining national registers. Thirty four cases with objectively diagnosed venous thrombosis and 641 controls were studied.

RESULTS

FVL (OR 11.6, 95% CI 3.6-33.6), age >35 vs. <25 (OR 6.3, 95% CI 1.7-23.1), and BMI >30 vs. <25 (OR 5.6, 95% CI 2.3-13.9) were associated with thrombosis. Overall absolute risk of a FVL carrier was 1 in 314. FVL interacted with age, BMI, and blood group. Population attributable risk proportion was 19% for FVL, 23% for age >35, 33% for BMI >25, and 35% for non-O blood group. Unexpectedly, the prevalence of FVL increased with age in controls.

CONCLUSIONS

FVL appeared as a strong risk factor for pregnancy-associated venous thrombosis. Especially in elderly overweight mothers, FVL may cause a substantial thrombosis risk. Further studies are needed to confirm the increased prevalence of FVL in elderly mothers with normal pregnancies.

Fibrinogen Aα-Thr312Ala and factor XIII-A Val34Leu polymorphisms in idiopathic venous thromboembolism

INTRODUCTION

Fibrinogen Aalpha-Thr312Ala and Factor XIII Val34Leu polymorphisms have been shown to modify fibrin clot structure and function. However, clinical studies have yielded conflicting results on their possible association with venous thromboembolism (VTE).

METHODS

We studied the association between these two polymorphisms and VTE in a hospital-based case-control study. We also assessed whether an independent or interactive association exists between Aalpha-fibrinogen Thr312Ala and FXIII Val34Leu polymorphisms and VTE. Fibrinogen Aalpha-Thr312Ala and FXIII Val34Leu polymorphisms were determined after PCR and restriction endonuclease digestion in 286 patients with idiopathic VTE and 286 age- and gender-matched controls. Results were analysed using a conditional logistic regression model for matched series.

RESULTS

The Fg-Aalpha 312Ala allele was associated with higher risk of VTE (OR 1.5; 95% CI: 1.1 to 2.2, p=0.01) while the FXIII 34Leu allele appeared protective (OR 0.7; 95% CI: 0.6 to 0.9, p=0.02). Both alleles demonstrated an independent association with idiopathic VTE after adjustment for Factor V Leiden and G20210A prothrombin polymorphisms. There was no interaction between the fibrinogen Aalpha-Thr312Ala and FXIII Val34Leu polymorphisms for the risk of VTE.

CONCLUSION

In this case-control study, the fibrinogen Fg-Aalpha 312Ala allele was associated with an increased risk of VTE. The FXIII 34Leu allele was also significantly associated with a lower risk of VTE without any interaction between the two polymorphisms studied.

The factor XIII Val34Leu polymorphism: is it protective against idiopathic venous thromboembolism?

The substitution of leucine for valine at amino acid position 34 of the factor XIII gene is commonly referred to as FXIII Val34Leu polymorphism. The homozygous leucine/leucine genotype has been reported to confer protection against venous thromboembolism, but previous studies have not evaluated a population limited to those with idiopathic venous thromboembolism. The primary objective of the study was to determine whether the FXIII Val34Leu polymorphism is independently associated with the occurrence of idiopathic venous thromboembolism. We prospectively enrolled consecutive patients with at least one objectively confirmed idiopathic venous thromboembolism. Friends of cases were recruited as controls and matched to cases by sex, ethnicity, and age. All participants were tested for the FXIII Val34Leu polymorphism in addition to several well-known thrombophilias. Data from 309 cases and 306 controls were analyzed. The FXIII leucine/leucine genotype was present in 4.9% of cases and 6.5% of controls. An adjusted odds ratio of 0.59 (95% confidence interval, 0.25-1.38) was found for the recessive model and 0.69 (95% confidence interval, 0.46-1.02) for the dominant model. Our results do not support an independent association of the FXIII Val34Leu polymorphism with idiopathic venous thromboembolism in our Caucasian Canadian study population.

Genetic polymorphisms of hemostasis genes and primary outcome of very low birth weight infants

BACKGROUND

Recent investigations have reported an influence of thrombophilic mutations and antithrombotic risk factors with development of intraventricular hemorrhage. It was our objective for this study to investigate the impact of genetic polymorphisms of hemostasis genes on the primary outcome measures of sepsis, bronchopulmonary dysplasia, intraventricular hemorrhage, and periventricular leukomalacia in a large cohort of very low birth weight infants.

METHODS

There were 586 very low birth weight infants enrolled prospectively in a multicenter trial between September 2003 and July 2005, and an additional 595 very low birth weight infants, who had been recruited in a previous prospective trial, were studied. DNA samples were taken by buccal swab, and genotypes of factor V Leiden mutation, prothrombin G20210A mutation, the factor VII-323 del/ins polymorphism, and the factor XIII-Val34Leu polymorphisms were determined by polymerase chain reaction and restriction enzyme digestion.

RESULTS

In contrast to data published previously, the frequency of intraventricular hemorrhage or periventricular leukomalacia was not significantly influenced by any of the genetic variants tested. Carriers of the factor XIII-Val34Leu polymorphism, however, had a higher sepsis rate and a longer period of hospital care compared with noncarriers. The factor VII-323 del/ins polymorphism was found to be a potential protective factor against bronchopulmonary dysplasia.

CONCLUSIONS

We could not confirm previously reported associations of hemostasis gene variants and development of intraventricular hemorrhage in very low birth weight infants. To better understand gene-disease associations in very low birth weight infants, the prospective development of large-scale cohorts with well-defined phenotypes and corresponding DNA samples is essential.

Factor XIII Val34Leu variant is protective against venous thromboembolism: a HuGE review and meta-analysis

It has been suggested that a G-to-T transition in exon 2 of the factor XIIIA gene resulting in a substitution of leucine for valine at amino acid 34 (FXIII Val34Leu) protects against venous thromboembolism (VTE). However, the evidence to date is insufficient to incorporate testing for the FXIII Val34Leu variant into clinical practice. To determine whether genotypes with the FXIII Val34Leu variant are protective against VTE, the authors performed a meta-analysis of 12 studies with genotyping for the FXIII Val34Leu variant (3,165 objectively diagnosed VTE cases and 4,909 controls). When a random-effects model was used, the combined odds ratios for VTE were 0.63 (95% confidence interval: 0.46, 0.86) for the homozygotes of the FXIII Val34Leu variant, 0.89 (95% confidence interval: 0.80, 0.99) for the heterozygotes, and 0.85 (95% confidence interval: 0.77, 0.95) for the homozygotes and heterozygotes combined. Potential sources of heterogeneity and potential bias were explored. The meta-analysis provided evidence that the FXIII Val34Leu variant has a small, but significant protective effect against VTE. Since VTE is a complex disorder, this information, along with results of ongoing studies to identify additional genetic factors underlying VTE, will be crucial in developing accurate risk profiles to identify individuals at higher risk of VTE.

Can haematological tests predict cardiovascular risk? The 2005 Kettle Lecture*

The risk of venous or arterial thrombosis is routinely assessed by clinical variables (risk factors) supplemented by measurement of blood lipids and glucose for arterial thrombotic events. Haematological tests that might play a role in risk prediction include haemostatic variables, haematocrit and inflammatory markers (erythrocyte sedimentation rate, plasma viscosity, white cell count). Recent epidemiological studies of these phenotypes and related genotypes are reviewed. For the risk prediction of first venous thrombosis, screening for thrombophilias in 'high-risk' situations does not appear clinically effective or cost-effective; with the possible exception of women considering oral hormone replacement therapy. General screening after a first venous event to predict recurrence (or risk in asymptomatic relatives) does not appear effective; with the possible exception of d-dimer, which requires further study. For risk prediction of first arterial thrombosis, screening adds little to prediction by current clinical risk scores. Screening of persons after a first arterial event, or with atrial fibrillation (e.g. with D-dimer for stroke prediction), requires further study. In conclusion, haematological tests have very limited roles in the prediction of cardiovascular risk, and should only be used according to evidence-based guidelines. The need for management studies is highlighted.

Issues concerning the laboratory investigation of inherited thrombophilia

Inherited thrombophilia, defined as an increased familial tendency to develop thrombosis, may be due to congenital deficiencies or abnormalities of antithrombin, protein C or protein S; to the presence of a point mutation in the factor V gene (G1691A, factor V Leiden) leading to a poor anticoagulant response to activated protein C; or to the presence of a mutation in the prothrombin gene (G20210A) leading to increased plasma levels of prothrombin. The laboratory investigation of inherited thrombophilia should be limited to patients with a history of venous thromboembolism and, if positive, to their family members even though they are still asymptomatic. There is no indication for indiscriminate screening of the general population or screening of asymptomatic women before prescribing oral contraceptives. Testing should be based on the phenotype for antithrombin, protein C and protein S; on the phenotype and genotype (factor V Leiden mutation) for activated protein C resistance; and on the genotype (G20210A mutation) for hyperprothrombinemia. Phenotypic testing should be performed no sooner than three months after acute thrombotic events and at least 2 weeks after discontinuation of oral anticoagulant treatment.

Factor XIII Val34Leu polymorphism and gamma-chain cross-linking at the site of microvascular injury in healthy and coumadin-treated subjects

Fibrin (Fn) cross-linking by activated factor (F) XIII is essential for clot stability. In vitro, a common Leu34 polymorphism of the FXIIIA-subunit increases the rate of thrombin-mediated FXIII activation, but not cross-linking activity upon complete FXIII activation. The effect of FXIII Val34Leu polymorphism on fibrin(ogen) cross-linking in vivo when vascular injury triggers the blood coagulation has not been studied yet. Using quantitative immunoblotting with antibodies raised against FXIIIA-subunits, fibrinogen, and gamma-gamma-dimers, the rates of FXIIIA cleavage and fibrin(ogen) cross-link formation in the fluid phase of 30-s blood samples collected at the site of microvascular injury were compared in the Leu34-positive and -negative healthy individuals and patients on long-term oral anticoagulation. In addition to accelerated FXIII activation, in healthy subjects the presence of FXIII Leu34 allele was associated with increased soluble gamma-gamma-dimer formation by 40% (1355 +/- 17 microg L(-1) for Leu34 carriers vs. 804.3 +/- 17 microg L(-1) for Leu34 non-carriers; P = 0.028) at the site of microvascular injury. This solution phase effect was abolished in coumadin-treated patients (369.4 +/- 75.9 microg L(-1) for Leu34 carriers vs. 290.5 +/- 35.9 microg L(-1) for Leu34 non-carriers; P > 0.05). The present study indicates that the Leu34 allele affects soluble gamma-gamma-dimer formation in untreated individuals, but not in those receiving acenocoumarol. Our data may help elucidate the impact of the FXIII Val34Leu polymorphism on Fn cross-linking in vivo and its modulation by oral anticoagulants.

Determinants of the APTT- and ETP-based APC sensitivity tests

BACKGROUND

A reduced sensitivity for activated protein C (APC) is associated with an increased risk of venous thrombosis even in the absence of the factor (F)V Leiden mutation. This risk has been demonstrated with two APC sensitivity tests, which quantify the effects of APC on the activated partial thromboplastin time (APTT) and the endogenous thrombin potential (ETP), respectively.

OBJECTIVES

We examined determinants of both APC sensitivity tests in the control group of the Leiden Thrombophilia Study (LETS).

METHODS

Multiple linear regression analysis was performed with normalized APC-SR(APTT) or APC-SR(ETP) as dependent variable and putative determinants [levels of FII, FV, FVII, FVIII, FIX, FX, FXI, FXII, FXIII A subunit, FXIII B subunit, protein S total, protein S free, protein C, tissue factor pathway inhibitor (TFPI) total, TFPI free, antithrombin and fibrinogen] as independent variables.

RESULTS AND CONCLUSIONS

The major determinant of the APTT-based test was FVIII level, followed by FII level. The ETP-based test was influenced most by free protein S and free TFPI levels. In both tests FXa formation plays a major role, as the effect of FVIII and TFPI on the tests seems to be executed via FXa. The ETP-based test was also strongly influenced by oral contraceptive use, even when we adjusted for all the clotting factors listed above. This means that the effect of oral contraceptives on the ETP-based test is not fully explained by the changes of coagulation factor levels investigated in this study, and that the molecular basis of acquired APC resistance during use of oral contraceptives remains to be established.

Fibrin stabilization (factor XIII), fibrin structure and thrombosis

Factor XIII (FXIII) is a zymogen that is converted into an active transglutaminase (FXIIIa) by the concerted action of thrombin and Ca2+. Its main task is to crosslink alpha-, and gamma-chains of fibrin and alpha2-plasmin inhibitor to fibrin. By this way FXIIIa strengthens fibrin and protects it from the prompt elimination by fibrinolytic system.The changes of FXIII level in thrombotic diseases are hardly explored and there are contradictory results concerning the protective effect of Val34Leu polymorphism against arterial or venous thrombosis. The results suggest that the thrombo-protective effect of Leu34 allele prevails only in certain genetic and/or environmental constellations.

Thrombophilia and the Risk for Hemodialysis Vascular Access Thrombosis

Vascular access thrombosis is the most common and costly complication in hemodialysis patients. The role of thrombophilia in access thrombosis is not established. A case-control study was conducted of 419 hemodialysis patients to determine whether thrombophilia was associated with arteriovenous fistula or graft thrombosis. Participants were enrolled from three in-center and five satellite dialysis units associated with a Canadian academic health science center that provides dialysis services in a catchment area of one million. Patients were tested for factor V Leiden, prothrombin gene mutation, factor XIII genotype, methylenetetrahydrofolate reductase genotype, lupus anticoagulant, anticardiolipin antibody, factor VIII, homocysteine, and lipoprotein (a) concentrations. Overall, 59 (55%) patients with access thrombosis had at least one thrombophilia compared with 122 (39%) patients without access thrombosis (unadjusted odds ratio [OR], 1.91; 95% confidence interval [CI], 1.23 to 2.98). After controlling for important risk factors, the association between any thrombophilia and access thrombosis remained (adjusted OR, 2.42; 95% CI, 1.47 to 3.99). For each additional thrombophilic disorder, the odds of access thrombosis increased significantly (adjusted OR, 1.87; 95% CI, 1.34 to 2.61). This study suggests that thrombophilia is associated with access thrombosis in dialysis patients. Large, multicenter, prospective cohort studies are needed to confirm the observations from this case-control study.

Elevated Clotting Factor Levels and Venous Thrombosis

Increased plasma levels of fibrinogen, factor VIII (FVIII), factor IX (FIX), factor XI (FXI) and prothrombin all were reported to be independent risk factors of venous thromboembolism (VTE). However there is only limited information on the molecular basis of these plasma phenotypes. In addition some of these plasma phenotypes may form clusters, which may point to defects in common pathways affecting biosynthesis or clearance. Uncertainties as to what should be considered the cut-off for an elevated plasma level and in some cases (FIX, FXI) the lack of published confirmatory and/or prospective studies, have delayed the incorporation of these parameters in thrombophilia screening procedures.

Analytical validation of the tag-it high-throughput microsphere-based universal array genotyping platform: application to the multiplex detection of a panel of thrombophilia-associated single-nucleotide polymorphisms

BACKGROUND

We have developed a novel, microsphere-based universal array platform referred to as the Tag-It platform. This platform is suitable for high-throughput clinical genotyping applications and was used for multiplex analysis of a panel of thrombophilia-associated single-nucleotide polymorphisms (SNPs).

METHODS

Genomic DNA from 132 patients was amplified by multiplex PCR using 6 primer sets, followed by multiplex allele-specific primer extension using 12 universally tagged genotyping primers. The products were then sorted on the Tag-It array and detected by use of the Luminex xMAP system. Genotypes were also determined by sequencing.

RESULTS

Empirical validation of the universal array showed that the highest nonspecific signal was 3.7% of the specific signal. Patient genotypes showed 100% concordance with direct DNA sequencing data for 736 SNP determinations.

CONCLUSIONS

The Tag-It microsphere-based universal array platform is a highly accurate, multiplexed, high-throughput SNP-detection platform.

Haplotypes of the EPCR gene, plasma sEPCR levels and the risk of deep venous thrombosis

BACKGROUND

Binding of protein C (PC) to the endothelial cell PC receptor (EPCR) stimulates PC activation by increasing the affinity of PC for the thrombin-thrombomodulin complex. A soluble form of this receptor (sEPCR) circulates in plasma and inhibits both PC activation and APC anticoagulant activity.

OBJECTIVES

The aim of this study was to investigate whether variations in the EPCR gene or plasma sEPCR levels are risk factors for deep venous thrombosis (DVT).

PATIENTS/METHODS

In a large case-control study, the Leiden Thrombophilia Study (LETS), sEPCR levels were measured by ELISA. All subjects were genotyped for three haplotype-tagging SNPs, enabling us to detect all four common haplotypes of the EPCR gene.

RESULTS

The distribution of sEPCR levels in the control population was trimodal and was genetically controlled by haplotype 3 (H3). This haplotype explained 86.5% of the variation in sEPCR levels. Carriers of two H3 alleles had higher sEPCR levels (439 ng mL(-1)) than carriers of one H3 allele (258 ng mL(-1)), which had higher levels than non-H3 carriers (94 ng mL(-1)). Haplotype 4 was associated with a slightly increased risk (OR = 1.4, 95%CI:1.0-2.2). The risk of subjects with sEPCR levels in the top quartile (>/= 137 ng mL(-1)) was increased compared to that of subjects in the first quartile (< 81 ng mL(-1)), but since there was no dose-response effect, it is most likely that low sEPCR levels reduce the risk of DVT.

CONCLUSIONS

Our data do not suggest a strong association between EPCR haplotypes and thrombosis risk, but low sEPCR levels appear to reduce the risk of DVT.

Interaction between oral contraceptive use and coagulation factor levels in deep venous thrombosis

Deep venous thrombosis is a multicausal disease, i.e. more than one risk factor needs to be present to cause the disease. Oral contraceptive use increases the risk of venous thrombosis but since not all women using oral contraceptives develop thrombosis, the presence of additional risk factors in patients is likely. The aim of this study was to assess the joint effect of oral contraceptive use and the levels of procoagulant factors (F)(FII, FV, FVII, FVIII, FIX, FX, FXI, FXII, FXIII and fibrinogen). Data of premenopausal women were re-analyzed in the Leiden Thrombophilia Study. The highest relative risks were observed for the combination of oral contraceptive use and high levels (>90th percentile) of FII (Odds Ratio [OR]OC+FII 10.1; 95% confidence interval [CI] 3.5-29.0), FV (OROC+FV 12.6; 95% CI 3.8-41.5), and FXI (OROC+FXI 11.9; 95% CI 3.6-39.2) and low levels (< 10th percentile) of FXII (OROC+FXII 12.3; 95% CI 2.4-63.0). No interaction was observed between oral contraceptive use and high levels of the other coagulation factors, i.e. the joint effect of these risk factors did not exceed the sum of the separate effects. The results of this study indicate that the risk for the joint effects of oral contraceptive use and coagulation factor levels are minor compared with the joint effect of oral contraceptive use and the FV Leiden mutation (RR > 30).