Inherited risk factors for venous thromboembolism

Mutation Ter462GlnextTer17 introduces a tail to C-terminus of protein C and causes venous thrombosis

Protein C (PC), a vitamin K-dependent serine protease zymogen in plasma, can be activated by thrombin-thrombomodulin(TM) complex, resulting in the formation of activated protein C (APC). APC functions to downregulate thrombin generation by inactivating active coagulation factors V(FVa) and VIII(FVIIIa). Deficiency in PC increases the risk of venous thromboembolism (VTE). We have identified two unrelated VTE patients with the same heterozygous mutation (c.1384 T > C, p.Ter462GlnextTer17) in PROC. To comprehend the role of this mutation in VTE development, we expressed recombinant PC-Ter462GlnextTer17 in mammalian cells and evaluated its characteristics using established coagulation assay systems. Functional studies revealed a significant impairment in the activation of the mutant by thrombin or thrombin-TM complex. Furthermore, APC-Ter462GlnextTer17 demonstrated diminished hydrolytic activity towards the chromogenic substrate S2366. APTT and FVa degradation assays showed that both the anticoagulant activity of the mutant protein was markedly impaired, regardless of whether protein S was present or absent. These results were further supported by a thrombin generation assay conducted using purified and plasma-based systems. In conclusion, the Ter462GlnextTer17 mutation introduces a novel tail at the C-terminus of PC, leading to impaired activity in both PC zymogen activation and APC's anticoagulant function. This impairment contributes to thrombosis in individuals carrying this heterozygous mutation and represents a genetic risk factor for VTE.

Impact of Inherited Thrombophilia in Women with Obstetric Antiphospholipid Syndrome: A Single-Center Study and Literature Review

Inherited thrombophilia (IT) has been implicated as a potential causal factor of adverse pregnancy outcomes (APOs), including recurrent miscarriage with and without the presence of antiphospholipid syndrome (APS). The aim of this study was to assess the prevalence and impact of IT on fetal-maternal outcomes and thrombotic risk in women within the spectrum of obstetric APS. Three hundred and twenty-eight women with APS-related obstetric morbidity ever pregnant were included. Of these, 74 met the APS classification criteria, 169 were non-criteria (NC)-APS, and 85 were seronegative (SN)-APS. Patients with other autoimmune diseases were excluded. APOs included early pregnancy loss, fetal death, preeclampsia, abruptio placentae, and preterm birth. Successful pregnancy was defined as the achievement of a live newborn. A literature search was also performed. The mean age of the overall group was 33.9 ± 5.3 years, and the patients were followed up for 35 (11-79) months. During the study period, there were 1332 pregnancies. Nearly 14% of the patients had an associated IT. IT patients more frequently received the standard-of-care (SoC) therapy. The presence of IT was not associated with worse maternal-fetal outcomes in patients treated with SoC treatment. Overall, IT patients had a lower frequency of newborns without treatment, especially those without definite APS. In addition, IT did not increase the risk of thrombosis during pregnancy or the postpartum period. A detailed analysis of the literature review identified only four publications related to our study and did not show conclusive evidence of the impact of IT on patients with obstetric APS. The group of women with APS-related obstetric morbidity and IT who did not receive treatment, especially those without definite APS, had a worse prognosis in terms of a live birth. However, with SoC therapy, the prognosis is similar in those patients without IT. The association of IT with APS does not seem to predispose to the development of thrombosis during pregnancy and/or the postpartum period.

Identifying novel biomarkers using proteomics to predict cancer-associated thrombosis

Comprehensive protein analyses of plasma are made possible by high-throughput proteomic screens, which may help find new therapeutic targets and diagnostic biomarkers. Patients with cancer are frequently affected by venous thromboembolism (VTE). The limited predictive accuracy of current VTE risk assessment tools highlights the need for new, more targeted biomarkers. Although coagulation biomarkers for the diagnosis, prognosis, and treatment of VTE have been investigated, none of them have the necessary clinical validation or diagnostic accuracy. Proteomics holds the potential to uncover new biomarkers and thrombotic pathways that impact the risk of thrombosis. This review explores the fundamental methods used in proteomics and focuses on particular biomarkers found in VTE and cancer-associated thrombosis.

Outcomes of venous thromboembolism in patients with inherited thrombophilia treated with direct oral anticoagulants: insights from the RIETE registry

While direct oral anticoagulants (DOACs) are frequently used to treat venous thromboembolism (VTE), the outcomes of patients with inherited thrombophilia (IT) receiving DOACs for VTE remain understudied. We used data from the international RIETE registry to compare the rates of VTE recurrences, major bleeding, and mortality during anticoagulant treatment in VTE patients with and without IT, grouped by the use of DOACs or standard anticoagulant therapy. Among 103,818 enrolled patients, 21,089 (20.3%) were tested for IT, of whom 8422 (39.9%) tested positive: Protein C deficiency 294, Protein S deficiency 726, Antithrombin deficiency 240, Factor V Leiden 2248, Prothrombin gene mutation 1434, combined IT 3480. Overall, 14,189 RIETE patients (6.2% with IT) received DOACs, and 89,629 standard anticoagulation (8.4% with IT), mostly with heparins followed by vitamin K antagonists. Proportions of patients receiving DOACs did not differ between IT-positive and IT-negative patients. Rates of VTE recurrence on anticoagulant treatment were highest in patients with AT deficiency (P < 0.01). Rates of on-treatment major bleeding and all-cause mortality were lowest among patients with Factor V Leiden (FVL) or PT G20210A mutations, compared with patients who tested negative. Patients with IT who received DOACs had lower rates of major bleeding than those receiving standard anticoagulation. Excluding FVL and Protein S deficiency, patients with IT had lower rates of VTE recurrence with DOACs than with standard anticoagulation. DOACs are equally safe and effective in VTE patients with IT, with lower bleeding rates than those on standard anticoagulation.

Thrombophilia genetic mutations and their relation to disease severity among patients with COVID-19

OBJECTIVES

Patients with COVID-19 infection appear to develop virus-induced hypercoagulability resulting in numerous thrombotic events. The aim of the present study was to determine the relationship between the thrombophilia genes mutations (prothrombin G20210A, factor V Leiden, and methyltetrahydrofolate reductase (MTHFR)) and the severity of COVID-19 patients.

DESIGN

Prospective cross-sectional study.

METHOD

One hundred and forty patients (80 adults and 60 children) were included in the current study. They were divided into the severe COVID-19 group and the mild COVID-19 group, with each group comprising 40 adults and 30 children. The patients were assessed for FV R506Q, FV R2H1299R, MTHFR A1298C, MTHFR C677T, and prothrombin gene G20210A polymorphisms. CBC, D-dimer, renal and liver function tests, hs-CRP, ferritin, and LDH were also assessed. Thrombotic events were clinically and radiologically documented.

RESULTS

Severe COVID-19 cases were significantly more frequent to have a heterozygous mutation for all the studied genes compared to mild COVID-19 cases (p<0.05 for all). Being mutant to gene FV R506Q carried the highest risk of developing a severe disease course (p<0.0001). Patients with abnormally high D-dimer levels were significantly more frequent to be heterozygous for FV R506Q, FV R2H1299R, and prothrombin gene G20210A (p = 0.006, 0.007, and 0.02, respectively).

CONCLUSION

We concluded that there is an evident relationship between severe COVID-19 and inherited thrombophilia. In the current study, FV R506Q gene mutation carried the highest risk of developing a severe COVID-19 disease course.

A study of recurrent life-threatening thrombosis accompanied with the duplication of the factor IX gene

Hereditary predisposition play an important role in thrombosis, especially in younger patients. Here we studied a young patient who experienced three different episodes of severe thromboses, some of which were life-threatening (pulmonary artery thrombosis, portal and mesenteric vein thrombosis, and arterial thrombosis of the lower leg). Blood levels of clotting related indicators were assessed. We screened 35 genes linked to thrombosis. We discovered a 756 kb duplication that spanned the F9 gene in region q27.1 of the X chromosome. The repeat includes the full F9 gene, thus, the patient had two functional copies of FIX with the FIX activity 192%. An identical repetition was found in the patient's mother. Both the patient and his mother had high, but variable, plasma FIX activities that promote coagulation. The patient's frequent, severe thrombolic events maybe attributed to the duplication of a big portion of the F9 gene and lupus anticoagulant positive.

Laboratory Evaluation of Antithrombin, Protein C, and Protein S

Thrombophilia is a complex disease process, clinically manifesting in various forms of venous thromboembolism. Although both genetic and acquired (or environmental) risks factors have been reported, the presence of a genetic defect (antithrombin [AT], protein C [PC], protein S [PS]) is considered three of the major contributing factors of thrombophilia. The presence of each of these risk factors can be established by clinical laboratory analysis; however, the clinical provider and laboratory personnel must understand the testing limitations and shortcomings associated with the assays for these factors to be able to ensure an accurate diagnosis. This article will describe the major pre-analytical, analytical, and post-analytical issues associated with the various types of assays and discuss evidence-based algorithms for analyzing AT, PC, and PS in plasma.

Deep sequencing of circulating miRNAs and target mRNAs level in deep venous thrombosis patients

Deep venous thrombosis is one of the most common peripheral vascular diseases that lead to major morbidity and mortality. The authors aimed to identify potential differentially expressed miRNAs and target mRNAs, which were helpful in understanding the potential molecule mechanism of deep venous thrombosis. The plasma samples of patients with deep venous thrombosis were obtained for the RNA sequencing. Differentially expressed miRNAs were identified, followed by miRNA-mRNA target analysis. Enrichment analysis was used to analyze the potential biological function of target mRNAs. GSE19151 and GSE173461 datasets were used for expression validation of mRNAs and miRNAs. 131 target mRNAs of 21 differentially expressed miRNAs were identified. Among which, 8 differentially expressed miRNAs including hsa-miR-150-5p, hsa-miR-326, hsa-miR-144-3p, hsa-miR-199a-5p, hsa-miR-199b-5p, hsa-miR-125a-5p, hsa-let-7e-5p and hsa-miR-381-3p and their target mRNAs (PRKCA, SP1, TP53, SLC27A4, PDE1B, EPHB3, IRS1, HIF1A, MTUS1 and ZNF652) were found associated with deep venous thrombosis for the first time. Interestingly, PDE1B and IRS1 had a potential diagnostic value for patients. Additionally, 3 important signaling pathways including p53, PI3K-Akt and MAPK were identified in the enrichment analysis of target mRNAs (TP53, PRKCA and IRS1). Identified circulating miRNAs and target mRNAs and related signaling pathways may be involved in the process of deep venous thrombosis.

A Mendelian randomization study of serum uric acid with the risk of venous thromboembolism

BACKGROUND

Observational studies have linked hyperuricemia with venous thromboembolism (VTE). We aimed to investigate whether there are causal relationships between uric acid levels and VTE and its subtypes, including deep venous thrombosis (DVT) of the lower extremities and pulmonary embolism (PE).

METHODS

We utilized Mendelian randomization (MR) analysis to estimate the causal association in European individuals. We extracted two sets of polygenic instruments strongly associated (p < 5 × 10^-8) with uric acid from the CKDGen consortium and UK biobank, respectively. Genetic associations with the risk of VTE, DVT, and PE were obtained from the FinnGen biobank. We used the inverse-variance weighted method as the preliminary estimate. Additionally, we employed MR-Egger, weighted median, and Mendelian randomization pleiotropy residual sum and outlier method as complementary assessments. Sensitivity analyses were performed to test for pleiotropic bias.

RESULTS

The genetically instrumented serum uric acid levels had no causal effects on VTE, DVT, and PE. Two sets of polygenic instruments used for exposure, along with three complementary MR methods, also yielded no significant association.

CONCLUSIONS

Our MR analysis provided no compelling evidence for a causal relationship of serum uric acid with the risk of VTE. This suggests that uric acid-lowering therapies in patients with hyperuricemia may not be effective in reducing the likelihood of developing VTE.

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.

Pathophysiological, immunogenetic, anatomopathological profile of thrombophilia in pregnancy

Thrombophilic states have been associated with early and/or late pregnancy loss and possibly other severe obstetrical complications. Pregnancy-induced hypercoagulability, increased stasis, and the consequences of inherited and acquired thrombophilia are just a few of the factors that contribute to the development of thrombosis in pregnancy. In this review, we illustrate the impact that these factors have on the development of thrombophilia during pregnancy. We also explore how thrombophilia impact pregnancy outcomes. Next, we discuss how human leukocyte antigen G plays a part in thrombophilia during pregnancy by regulating cytokine release to prevent trophoblastic cell invasion and maintain local immunotolerance constant. Human leukocyte antigen class E is briefly explored with thrombophilia in pregnancy. Regarding the anatomopathologic aspect, we describe the different histopathological lesions of the placenta found in women with thrombophilia.

Laboratory Evaluation of Thrombophilia

Venous thromboembolism (VTE) occurs typically in the veins of the lower extremities and/or as pulmonary embolism. There is a myriad of causes of VTE ranging from provoked causes (e.g., surgery, cancer) to unprovoked causes (e.g., inherited abnormalities) or multiple factors that combine to initiate the cause. Thrombophilia is a complex, multi-factorial disease that may result in VTE. The mechanism(s) and causes of thrombophilia are complex and not completely understood. In healthcare today, only some answers about the pathophysiology, diagnosis, and prevention of thrombophilia have been elucidated. The laboratory analysis for thrombophilia is not consistently applied, and has changed over time, but remains varied by providers and laboratories as well. Both groups must establish harmonized guidelines for patient selection and appropriate conditions for analysis of inherited and acquired risk factors. This chapter discusses the pathophysiology of thrombophilia, and evidence-based medicine guidelines discuss the optimum laboratory testing algorithms and protocols for selection and analyzing VTE patients to ensure a cost-effective use of limited resources.

Favourable outcome of multisystem venous thrombosis associated with novel SERPINC1 mutation after treated with dabigatran: a case report with 7-year follow-up

BACKGROUND

Mutations in SERPINC1 lead to deficiency in antithrombin (AT) which is an endogenous anticoagulant of normal hemostasis and could result in venous thromboembolism (VTE).

CASE PRESENTATION

A 61-year-old male patient with recurrent thrombosis returned to the hospital with multiple cerebral thrombosis after voluntary cessation of dabigatran therapy. Laboratory tests revealed a type I AT deficiency in this patient and further whole exome sequencing (WES) identified a novel heterozygous frameshift duplication (c.233_236dup, p.Val80Alafs*26) in SERPINC1 gene. Long-term dabigatran treatment was given and no recurrence or side effects were found within the followed 5 years.

CONCLUSION

A multisystem VTE patient with a novel SERPINC1 mutation (c.233_236dup, p.Val80Alafs*26) reached a favourable outcome after dabigatran treatment.

Genetic risk and incident venous thromboembolism in middle-aged and older adults following COVID-19 vaccination

BACKGROUND

COVID-19 vaccination has been associated with increased venous thromboembolism (VTE) risk. However, it is unknown whether genetic predisposition to VTE is associated with an increased risk of thrombosis following vaccination.

METHODS

Using data from the UK Biobank, which contains in-depth genotyping and linked vaccination and health outcomes information, we generated a polygenic risk score (PRS) using 299 genetic variants. We prospectively assessed associations between PRS and incident VTE immediately after first- and the second-dose vaccination and among historical unvaccinated cohorts during the pre- and early pandemic. We estimated hazard ratios (HR) for PRS-VTE associations using Cox models.

RESULTS

Of 359 310 individuals receiving one dose of a COVID-19 vaccine, 160 327 (44.6%) were males, and the mean age at the vaccination date was 69.05 (standard deviation [SD] 8.04) years. After 28- and 90-days' follow-up, 88 and 299 individuals developed VTE, respectively, equivalent to an incidence rate of 0.88 (95% confidence interval [CI] 0.70-1.08) and 0.92 (0.82-1.04) per 100 000 person-days. The PRS was significantly associated with a higher risk of VTE (HR per 1 SD increase in PRS, 1.41 (1.15-1.73) in 28 days and 1.36 (1.22-1.52) in 90 days). Similar associations were found in the historical unvaccinated cohorts.

CONCLUSIONS

The strength of genetic susceptibility with post-COVID-19-vaccination VTE is similar to that seen in historical data. Additionally, the observed PRS-VTE associations were equivalent for adenovirus- and mRNA-based vaccines. These findings suggest that, at the population level, the VTE that occurred after the COVID-19 vaccination has a similar genetic etiology to the conventional VTE.

Evolving Knowledge on Primary and Secondary Prevention of Venous Thromboembolism in Carriers of Hereditary Thrombophilia: A Narrative Review

The association between heritability of venous thromboembolism (VTE) and thrombophilia was first reported clinically in 1956, later followed by the first description of a congenital cause of hypercoagulability-antithrombin deficiency-in 1965. Since then, our knowledge of hereditary causes of hypercoagulability, which may predispose carriers to VTE has improved greatly. Novel genetic defects responsible for severe thrombophilia have been recently identified and we have learned that a wide range of interactions between thrombophilia and other genetic and acquired risk factors are important determinants of the overall individual risk of developing VTE. Furthermore, therapeutic strategies in thrombophilic patients have benefited significantly from the introduction of direct oral anticoagulants. The present review is an overview of the current knowledge on the mechanisms underlying inherited thrombophilia, with a particular focus on the latest achievements in anticoagulation protocols and prevention strategies for thrombosis in carriers of this prothrombotic condition.

Evolving Knowledge on Primary and Secondary Prevention of Venous Thromboembolism in Carriers of Hereditary Thrombophilia: A Narrative Review

The association between heritability of venous thromboembolism (VTE) and thrombophilia was first reported clinically in 1956, later followed by the first description of a congenital cause of hypercoagulability-antithrombin deficiency-in 1965. Since then, our knowledge of hereditary causes of hypercoagulability, which may predispose carriers to VTE has improved greatly. Novel genetic defects responsible for severe thrombophilia have been recently identified and we have learned that a wide range of interactions between thrombophilia and other genetic and acquired risk factors are important determinants of the overall individual risk of developing VTE. Furthermore, therapeutic strategies in thrombophilic patients have benefited significantly from the introduction of direct oral anticoagulants. The present review is an overview of the current knowledge on the mechanisms underlying inherited thrombophilia, with a particular focus on the latest achievements in anticoagulation protocols and prevention strategies for thrombosis in carriers of this prothrombotic condition.

Total knee arthroplasty in patients with haemophilic arthropathy is effective and safe according to the outcomes at a mid-term follow-up

BACKGROUND

Haemophilic arthropathy (HA), a common complication of haemophilia, is secondary to recurrent joint bleeding and increases the prevalence of end-stage osteoarthritis (OA). Total knee arthroplasty (TKA) is a reliable treatment for haemophilia patients. This study was performed to evaluate the mid-term outcomes of TKA for end-stage HA. We hypothesized that the rate of complications of TKA is higher for patients with haemophilia than for patients without haemophilia.

METHODS

Patients with HA undergoing TKA from January 2015 to December 2016 in our centre were retrospectively reviewed. All patients were managed by a multidisciplinary team. The improvements in flexion contracture, range of motion (ROM), Knee Society Score (KSS; clinical and functional), Visual Analogue Scale (VAS) score, and satisfaction at final follow-up were analysed to evaluate the effectiveness of TKA in HA. The complications were analysed to evaluate the safety of TKA in HA.

RESULTS

Twenty-eight patients (32 knees) were included in the study. The follow-up was 69.1 ± 5.1 months. Significant differences between the preoperative and final follow-up values of flexion contracture (which changed from 21.1 ± 6.5° to 14.3 ± 4.1°, P < 0.001), ROM (from 53.9 ± 15.0° to 70.3 ± 16.3°, P < 0.001), clinical KSS (from 33.5 ± 14.4° to 62.7 ± 9.5°, P < 0.001), functional KSS (from 46.1 ± 15.5° to 62.9 ± 9.7°, P < 0.001), and VAS score (from 6.8 ± 1.4 to 4.9 ± 1.3, P < 0.01) were observed. Importantly, the incidence of complications was 15.6% and the satisfaction was 100% in our mid-term study.

CONCLUSION

Under elaborative and comprehensive management, TKA is effective and safe in patients with advanced HA on the basis of mid-term follow-up outcomes.

Sex‐specific aspects of venous thromboembolism: What is new and what is next?

Men seem to have a higher intrinsic risk of venous thromboembolism (VTE) than women, regardless of age. To date, this difference has not been explained. By integrating state‐of‐the‐art research presented at the International Society on Thrombosis and Haemostasis Congress of 2021 with the available literature, we address potential explanations for this intriguing risk difference between men and women. We discuss the role of exogenous and endogenous sex hormones as the most important known sex‐specific determinants of VTE risk. In addition, we highlight clues on the role of sex hormones and VTE risk from clinical scenarios such as pregnancy and the polycystic ovary syndrome. Furthermore, we address new potential sex‐specific risk factors and unanswered research questions, which could provide more insight in the intrinsic risk difference between men and women, such as body height and differences in body fat distribution, leading to dysregulation of metabolism and inflammation.

Use of the von Willebrand factor concentrate with low factor VIII content to manage patients with inherited von Willebrand disease requiring surgical or secondary long-term prophylaxis: An expert opinion paper from an Italian panel

OBJECTIVES

The present review aims to summarize the state-of-the-art von Willebrand disease (VWD) treatment focusing on specific clinical settings (obstetrics, surgery, long-term prophylaxis and comorbidities) as well as on the use of a Von Willebrand factor (VWF) concentrate with low FVIII content.

METHODS

Literature research and case reports.

RESULTS AND CONCLUSIONS

Considering that patients affected by VWD have an intact ability to synthesize FVIII, in order to avoid excessive levels of FVIII, a highly purified plasma VWF concentrate with low FVIII content could be particularly useful in those patients and clinical circumstances at high thrombotic risk as well as for long-term prophylaxis. When deciding the optimal therapeutic strategy, physicians should take into account both the patient's history and the differences among available concentrates according to the clinical situations requiring treatment.

Two SERPINC1 variants affecting N-glycosylation of Asn224 cause severe thrombophilia not detected by functional assays

Antithrombin deficiency, the most severe congenital thrombophilia, might be underestimated, as some pathogenic variants are not detected by routine functional methods. We have identified two new SERPINC1 variants, p.Glu227Lys and p.Asn224His, in four unrelated thrombophilic patients with early and recurrent thrombosis that had normal antithrombin activity. In one case, the mutation was identified by whole genome sequencing, while in the 3 remaining cases, the mutation was identified by sequencing SERPINC1 based on a single functional positive finding supporting deficiency. The two variants shared a common functional defect, an impaired or null N-glycosylation of Asn224 according to a eukaryotic expression model. Carriers had normal anti-FXa or anti-FIIa activities, but impaired anti-FVIIa activity and a detectable loss of inhibitory function when incubating the plasma 1 hour at 41ºC. Moreover, the beta glycoform of the variants, lacking two N-glycans, had reduced secretion, increased heparin affinity, no inhibitory activity, and a potential dominant negative effect. These results explain the increased thrombin generation observed in carriers. Mutation experiments reflected the role that Lysine residues close to the N-glycosylation sequon have in impairing the efficacy of N-glycosylation. Our study shows new elements involved in the regulation of N-glycosylation, a key post-translational modification that, according to our results affects folding, secretion and function, providing new evidence of the pathogenic consequence of an incorrect N-glycosylation of antithrombin. This study supports that antithrombin deficiency is underestimated and encourages the development of new functional and genetic tests to diagnose this severe thrombophilia.

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.

Identification of the novel G250R variant indicates a role for Thrombomodulin in modulating the risk for venous thromboembolism

Thrombomodulin displays anticoagulant properties through thrombin binding and protein C activation. In close relatives who had a history of recurrent VTE, a missense variant (G250R) in the EGF-1 domain was identified. In an asymptomatic 250R carrier, higher thrombin generation plasma values were found. Evaluation of cells transfected with the wild-type or the mutant construct using imaging technologies and flow cytometry provided evidences that the 250R variant significantly decreased protein localization on cell membrane. The different pattern of cell distribution suggested that the 250R variant is not able to sufficiently target the plasma membrane. Present findings add information to characterize protein structure-function relationships, further suggesting that misfolding of the protein modulates the expression of mature protein. Functional analyses of the 250R variant increase our understanding of the role of Thrombomodulin in coagulation and support the hypothesis that gene variants reducing protein functionality cause deficiency and behave as a thrombophilic risk factor.

Genetic Variants in the Protein S ( PROS1 ) Gene and Protein S Deficiency in a Danish Population

Protein S (PS) deficiency is a risk factor for venous thromboembolism (VTE) and can be caused by variants of the gene encoding PS ( PROS1 ). This study aimed to evaluate the clinical value of molecular analysis of the PROS1 gene in PS-deficient participants. We performed Sanger sequencing of the coding region of the PROS1 gene and multiplex ligation-dependent probe amplification to exclude large structural rearrangements. Free PS was measured by a particle-enhanced immunoassay, while PS activity was assessed by a clotting method.

A total of 87 PS-deficient participants and family members were included. In 22 index participants, we identified 13 PROS1 coding variants. Five variants were novel. In 21 index participants, no coding sequence variants or structural rearrangements were identified. The free PS level was lower in index participants carrying a PROS1 variant compared with index participants with no variant (0.51 [0.32–0.61] vs. 0.62 [0.57–0.73] × 10 ³ IU/L; p  < 0.05). The p.(Thr78Met) variant was associated with only slightly decreased free PS levels (0.59 [0.53–0.66] × 10 ³ IU/L) compared with the p.(Glu390Lys) variant (0.27 [0.24–0.37] × 10 ³ IU/L, p  < 0.01). The frequency of VTE in participants with a coding PROS1 variant was 43 and 17% in the group with normal PROS1 gene ( p  = 0.05).

In conclusion, we report 13 PROS1 coding variants including five novel variants. PS levels differ by PROS1 variant and the frequency of VTE was higher when a coding PROS1 variant was present. Hence, molecular analysis of the PROS1 gene may add clinical value in the diagnostic work-up of PS deficiency.

Data-driven analysis of the kinetics of the JAK2V617F allele burden and blood cell counts during hydroxyurea treatment of patients with polycythemia vera, essential thrombocythemia, and primary myelofibrosis

BACKGROUND

Hydroxyurea (HU) treatment of patients with essential thrombocythemia (ET), polycythemia vera (PV), and primary myelofibrosis (PMF) (MPNs) normalizes elevated blood cell counts within weeks in the large majority of patients. Studies on the impact of HU upon the kinetics of the JAK2V617F allele burden, leukocyte, and platelet counts over time are scarce.

PURPOSE

Using data-driven analysis as a novel tool to model the kinetics of the JAK2V617F allele burden and blood cell counts over time during treatment with HU.

MATERIAL AND METHODS

Using serial measurements of JAK2V617F and correlation analysis of routine hematological values (the Hb-concentration, leukocyte count, platelet count, and lactic dehydrogenase), we present a detailed description and analysis of the kinetics of the JAK2V617F, leukocyte, and platelet counts and lactic dehydrogenase in 27 patients (PV = 18; ET = 7; PMF = 2), who were followed in the Danish randomized trial (DALIAH). To further analyze the JAK2V617F kinetics, we use a machine learning clustering algorithm to group the response patterns.

RESULTS

Response patterns were highly heterogeneous, with clustering resulting in 3 groups and 3 outliers. In the large majority of patients, HU treatment was initially associated with a modest decline in the JAK2V617F allele burden in concert with a decline in leukocyte and platelet counts. However, HU did not induce a sustained and continuous decrease in the JAK2V617F allele burden.

CONCLUSION

Using data-driven analysis of the JAK2V617F allele burden, leukocyte, and platelet kinetics during treatment with HU, we have shown that HU does not induce a sustained decrease in the JAK2V617F allele burden and neither induces sustained normalization of elevated cell counts in MPN patients. Our results may explain why MPN patients during treatment with HU still have a substantially increased risk of thrombosis.

ABO Blood Groups and Thrombophilia Markers in Patients With Unstimulated Thrombosis in Kurdistan Region of Iraq

Thromboembolism (TE) is a complex disease caused by various acquired and inherited factors. The common mutations; factor V Leiden G1691A (FVL G1691A), prothrombin G20210A (PTG20210A), and methylene tetrahydrofolate reductase C677T (MTHFR C677T) are important inherited causes in both venous and arterial thrombosis. The association between ABO blood groups and thrombophilia has been noted by researchers. We aimed to determine the frequency and association of ABO blood groups as a risk factor along with 3 thrombophilia mutations and another 3 thrombophilia markers in a group of patients with unstimulated thrombosis. In a prospective case-control study, we focused on 100 samples, 50 patients with documented thrombosis as well as 50 healthy age-matched controls. Multiplex polymerase chain reaction and reverse hybridization to oligonucleotide particular probes were employed to detect FVL G1691A, PT G20210A, and MTHFR C677T mutations. Analysis of other thrombophilia markers including protein C (PC), protein S (PS), and antithrombin (AT) assays was also performed. ABO blood group typing was done according to standard methods. Non-O blood group was significantly more frequent among cases than controls (76% vs 54%) with high odds of TE (odds ratio [OR] = 2.69). Positivity for at least 1 thrombophilia marker was more in cases (60%) than controls (34%; OR = 2.9). The combined effect of non-O blood group and thrombophilia markers raised the risk of TE (OR = 4.16, P = .001), particularly FVL (OR = 6.76). This study illustrates that harboring the non-O blood group poses an additive effect with other thrombophilia markers in the causation of TE.

Direct Oral Anticoagulants in Patients With Inherited Thrombophilia and Venous Thromboembolism: A Prospective Cohort Study

Background

In this prospective cohort study, we aimed to evaluate the efficacy and safety of direct oral anticoagulants (DOACs) versus heparin/vitamin K antagonists for the treatment of venous thromboembolism (VTE) in patients with inherited thrombophilia.

Methods and Results

We enrolled consecutive patients with acute VTE and inherited thrombophilia treated with DOACs (cases) or heparin/vitamin K antagonists (controls), matched for age, sex, ethnicity, and thrombophilia type. End points were VTE recurrence and bleeding complications; residual vein thrombosis and post‐thrombotic syndrome; VTE recurrence after anticoagulant discontinuation. Two hundred fifty‐five cases (age 52.4±17.3 years, Female 44.3%, severe thrombophilia 33.1%) and 322 controls (age 49.7±18.1 years, Female 50.3%, severe thrombophilia 35.1%) were included. The cumulative incidence of VTE recurrence during anticoagulation was 1.09% in cases versus 1.83%, adjusted hazard ratio (HR) 0.67 (95% CI, 0.16–2.77). The cumulative incidence of bleeding was 10.2% in cases versus 4.97%, HR 2.24 (95% CI 1.10–4.58). No major bleedings occurred in cases (versus 3 in controls). No significant differences regarding residual vein thrombosis and post‐thrombotic syndrome. After anticoagulant discontinuation, DOACs yielded a significantly lower 2‐year VTE recurrence risk versus traditional anticoagulants (HR, 0.61 [95% CI, 0.47–0.82]).

Conclusions

DOACs and heparin/vitamin K antagonists showed a similar efficacy in treating VTE in patients with thrombophilia. Although major bleeding episodes were recorded solely with heparin/vitamin K antagonists, we noted an overall increased bleeding rate with DOACs. The use of DOACs was associated with a lower 2‐year risk of VTE recurrence after anticoagulant discontinuation.

Oral Contraceptives and Venous Thromboembolism: Focus on Testing that May Enable Prediction and Assessment of the Risk

Combined oral contraceptives (COCs) induce several changes in the levels of coagulation factors. The levels of procoagulant factors are often increased, while levels of anticoagulant factors are decreased. Fibrinolysis is also affected, even if the effect seems to be more counterbalanced by opposite regulation of profibrinolytic and antifibrinolytic factors. These effects on hemostasis are more pronounced with third- or fourth-generation COC compared with second-generation COC. Venous thromboembolism (VTE) risk increases when multiple risk factors, including genetic and environmental, are present simultaneously. COC use causes changes in coagulation that modify the prothrombotic state induced by preexisting hemostatic alterations in a supra-additive manner. Therefore, testing appears to be of importance not only before implementing COC but also to monitor any potential thrombogenicity induced by COC therapy. Inherited genetic factors, such as factor V Leiden, G20210A prothrombin mutation, antithrombin, protein C or protein S deficiencies, non-O blood group, as well as CYP2C9*2 and the rs4379368 mutations, have all been identified as genetic predictive risk factors of VTE in women. Nevertheless, the screening of these genetic biomarkers is not capable of assessing the phenotypic expression of the risk. This review will focus on the different options for screening the thrombogenic status in this population. Specific attention will be given to the endogenous thrombin potential-based activated protein C resistance, a test aiming at assessing the thrombogenicity induced by hormonal therapies and inherited or acquired thrombophilia.

Outcomes of symptomatic venous thromboembolism after haploidentical donor hematopoietic stem cell transplantation and comparison with human leukocyte antigen-identical sibling transplantation

BACKGROUND

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is regarded as a curative therapy for majority of hematologic malignancies and some non-malignant hematologic diseases. Venous thromboembolism (VTE) has become increasingly recognized as a severe complication following allogeneic hematopoietic stem cell transplantation (allo-HSCT).

OBJECTIVES

To show the characteristics of VTE after haploidentical donor hematopoietic stem cell transplantation (HID-HSCT) and make comparisons with matched related donor HSCT (MRD-HSCT).

PATIENTS/METHODS

A retrospective nested case-control study design was used, cases with VTE and matched controls were selected, with 3534 patients underwent HID-HSCT and 1289 underwent MRD-HSCT.

RESULTS

During follow-up, 114 patients with VTE were identified. The incidence of VTE in HID-HSCT group was similar to that of MRD-HSCT group (2.4% versus 2.3%, P = 0.92). In HID-HSCT group, VTE occurred at a median time of 92.5 days, which was earlier than MRD-HSCT group (243.5 days). For HID-HSCT, advanced disease status, cardiovascular risk factors, acute graft-versus-host disease (aGVHD), and relapse were the independent risk factors for VTE. For MRD-HSCT, cardiovascular risk factors, aGVHD, and relapse were associated with VTE. Overall survival (OS) of patients following HID-HSCT and MRD-HSCT were similar, but the OS in patients with VTE was significantly lower than patients without VTE.

CONCLUSIONS

There was no statistical difference in the incidence of VTE after HID-HSCT compared with MRD-HSCT. The development of VTE adversely impacted the OS after allo-HSCT.

Impact of Genetically Predicted Red Blood Cell Traits on Venous Thromboembolism: Multivariable Mendelian Randomization Study Using UK Biobank

Background

Red blood cell (RBC) transfusion and erythropoiesis‐stimulating agent administration are cornerstones of clinical practice, yet concerns exist as to potential increased risk of thrombotic events. This study aims to identify RBC traits most relevant to venous thromboembolism (VTE) and assess their genetically predicted effects on VTE in the general population.

Methods and Results

We used multivariable mendelian randomization with bayesian model averaging for exposure selection. We obtained genetic variants predicting any of 12 RBC traits from the largest genome‐wide association study of hematological traits (173 480 participants of European ancestry) and applied them to the UK Biobank (265 424 white British participants). We used univariable mendelian randomization methods as sensitivity analyses for validation. Among 265 424 unrelated participants in the UK Biobank, there were 9752 cases of VTE (4490 men and 5262 women). Hemoglobin was selected as the plausible important RBC trait for VTE (marginal inclusion probability=0.91). The best‐fitting model across all RBC traits contained hemoglobin only (posterior probability=0.46). Using the inverse variance–weighted method, genetically predicted hemoglobin was positively associated (odds ratio, 1.21 per g/dL unit of hemoglobin; 95% CI, 1.05–1.41) with VTE. Sensitivity analyses (mendelian randomization–Egger, weighted median, and mendelian randomization pleiotropy residual sum and outlier test) gave consistent estimates.

Conclusions

Endogenous hemoglobin is the key RBC trait causing VTE, with a detrimental effect in the general population on VTE. Given men have higher hemoglobin than women, this finding may help explain the sexual disparity in VTE rates. The benefits of therapies and other factors that raise hemoglobin need to be weighed against their risks.

Genetic and environmental factors associated with homocysteine concentrations in a population of healthy young adults. Analysis of the MAGNETIC study

BACKGROUND AND AIMS

Elevated homocysteine concentration is associated with a higher risk of cardiovascular disease. The aim of our study was to determine the environmental and genetic factors associated with serum homocysteine concentration in healthy young adults. Moreover, we aimed to determine the cutoff value of homocysteine concentration for predicting unfavorable MTHFR genotype and to investigate whether this association is modified by dietary patterns and serum folate status.

METHODS AND RESULTS

A total of 744 healthy individuals, aged 18-35 years, were included in the study. Diet quality was assessed by establishing diet quality scores and adherence to the pro-Healthy Diet Index (pHDI) and non-Healthy Diet Index (nHDI). Genotyping was performed using the TaqMan method. Multivariate analysis showed that pHDI, creatinine, folate concentrations, and the T/T genotype of the C677T polymorphism in MTHFR, as well as the interaction between the T/T genotype of MTHFR (C677T polymorphism) and folate level, were most strongly related to homocysteine concentrations. The specificity of a homocysteine >13.1 μmol/l in predicting T/T homozygous status was 76% (area under the curve 0.68).

CONCLUSION

Healthy dietary patterns, folate, and creatinine levels, as well as the C677T polymorphism, proved to be the strongest predictors of homocysteine concentrations. T/T genotype of MTHFR modifies the relationship between folate and homocysteine.

Congenital antithrombin deficiency in patients with splanchnic vein thrombosis

BACKGROUND AND AIMS

Splanchnic vein thromboses (SVT) are a rare condition that can be life-threatening. The most severe thrombophilia associated to SVT is antithrombin (AT) deficiency, usually caused by SERPINC1 mutations. Although transitory AT deficiencies and congenital disorders of the N-glycosylation pathways (CDG) have been recently reported as causes of AT deficiency, the current AT clinical screening still only includes anti-FXa activity. This study aims to (a) improve the detection of AT deficiency in SVT and (b) characterize the features of AT deficiency associated with SVT.

METHODS

The study was performed in 2 cohorts: (a) 89 SVT patients with different underlying etiologies but in whom AT deficiency had been ruled out by classical diagnostic methods; and (b) 271 unrelated patients with confirmed AT deficiency and venous thrombosis. AT was evaluated by functional (anti-FXa and anti-FIIa) and immunological methods (ELISA, crossed immunoelectrophoresis, western blot), and SERPINC1 sequencing was performed.

RESULTS

In 4/89 patients (4.5%) additional alterations in AT were found (two had SERPINC1 mutations, one had a specific variant causing transient AT deficiency and one patient had CDG). In 11 of the 271 patients (4.1%) with AT deficiency and thrombosis, thrombosis was located at the splanchnic venous territory.

CONCLUSIONS

Antithrombin deficiency may be underdiagnosed by current clinical screening techniques. Therefore, a comprehensive AT evaluation should be considered in cases of rethrombosis or doubtful interpretation of anti-FXa activity levels. SVT is a relatively common localization of the thrombotic event in patients with congenital AT deficiency.

Prothrombin Arg541Trp Mutation Leads to Defective PC (Protein C) Pathway Activation and Constitutes a Novel Genetic Risk Factor for Venous Thrombosis

OBJECTIVE

Defective PC (protein C) pathway predisposes patients to venous thromboembolism (VTE) and is mostly, but not exclusively, attributed to hereditary PC or PS (protein S) deficiencies and activated PC resistance caused by factor V Leiden mutation. Approach and Results: In a patient with acute mesenteric venous thrombosis and positive family history of VTE associated with the impaired PC pathway function determined by thrombin generation test, we identified a novel heterozygous prothrombin mutation p.Arg541Trp. Two more patients with positive family history of VTE carrying the same mutation were identified in a cohort of another 373 unrelated patients, making an overall prevalence of 0.8%. Family investigation revealed 11 individuals in the 3 pedigrees harboring the heterozygous prothrombin p.Arg541Trp mutation, and 8 of them (72%) had experienced episodes of VTE. Functional studies indicated the mutation moderately decreased procoagulant activity of prothrombin and had mild impact on the inactivation of thrombin by its inhibitor antithrombin. However, the amino acid residue substitution significantly compromised PC activation by thrombin, both in the absence and presence of soluble thrombomodulin, and thus rendered prothrombin function procoagulant biased.

CONCLUSIONS

In summary, the prothrombin p.Arg541Trp mutation constitutes a new genetic risk factor of VTE by impairing function of PC pathway and tilting thrombin's procoagulant activity over anticoagulant function.

Long-term Impact of Bariatric Surgery on Venous Thromboembolic Risk: A Matched Cohort Study

OBJECTIVE

The aim of this study is to evaluate the effect of bariatric surgery on long-term risk of VTEs in a large cohort of patients with obesity.

BACKGROUND

Obesity is a well-established risk factor for VTEs, such as pulmonary embolism and deep vein thrombosis. The rising prevalence of obesity and its associated co-morbidities, including VTE, represent a growing public health issue.

METHODS

A nested, retrospective matched cohort study was designed and conducted on prospectively collected national electronic healthcare records data from the Clinical Practice Research Datalink. Eight thousand, one hundred twelve patients were included in the study: the 4056 patients on the database who had undergone bariatric surgery, and equal numbers of age, sex, and body mass index matched controls. The primary endpoint was the occurrence of VTEs; secondary endpoints were the occurrence of deep vein thrombosis alone, pulmonary embolism alone.

RESULTS

Patients were followed up for a median of 10.7 years. The bariatric surgery cohort had a significantly lower occurrence of the primary outcome [hazard ratio (HR) 0.601; 95% confidence interval (CI) 0.430-0.841, P = 0.003]; mainly driven by a reduction in deep vein thrombosis (HR 0.523; 95% CI 0.349-0.783, P = 0·002) and not in pulmonary embolism (HR 0.882; 95% CI 0.511-1.521, P = 0.651).

CONCLUSIONS

The results of this nation-wide study set out to characterize the impact of bariatric surgery on long-term risk of thromboembolic events outline a significant reduction in thromboembolic events, driven by a reduction in deep vein thrombosis.

High factor VIII levels and arterial thrombosis: illustrative case and literature review

Thrombotic disorders are one of the most common causes of morbidity and mortality in developing and developed countries. Several well-known genetic traits underlie predisposition to venous thrombosis. In particular, high factor VIII levels are a risk factor for venous thrombosis and coronary artery disease (CAD). However, similar insight into the genetic component of arterial thrombosis predisposition has not materialized fully, despite considerable effort. The authors present an illustrative case of a 32-year-old Saudi Arabian patient with peripheral arterial thrombosis whose only identifiable risk factor were high factor VIII levels. We also provide a comprehensive review of the current state of knowledge concerning the role of high factor VIII levels in determining the risk of arterial thrombosis or ischemic heart disease (IHD). We conclude that high factor VIII levels are a risk factor for thrombosis, with a greater impact on venous than on arterial thrombosis. However, due to a lack of international consensus on methods for the laboratory testing of factor VIII levels in plasma, we would not currently recommend the measurement of factor VIII levels as part of routine thrombophilia screening.

Elevated thrombin generation in patients with congenital disorder of glycosylation and combined coagulation factor deficiencies

BACKGROUND

Congenital disorders of glycosylation are rare inherited diseases affecting many different proteins. The lack of glycosylation notably affects the hemostatic system and leads to deficiencies of both procoagulant and anticoagulant factors.

OBJECTIVE

To assess the hemostatic balance in patients with multiple coagulation disorders by using a thrombin generation assay.

METHOD

We performed conventional coagulation assays and a thrombin generation assay on samples from patients with congenital disorder of glycosylation. The thrombin generation assay was performed before and after activation of the protein C system by the addition of soluble thrombomodulin.

RESULTS

A total of 35 patients were included: 71% and 57% had low antithrombin and factor XI levels, respectively. Protein C and protein S levels were abnormally low in 29% and 26% of the patients, respectively, whereas only 11% displayed low factor IX levels. Under baseline conditions, the thrombin generation assay revealed a significantly higher endogenous thrombin potential and thrombin peak in patients, relative to controls. After spiking with thrombomodulin, we observed impaired involvement of the protein C system. Hence, 54% of patients displayed a hypercoagulant phenotype in vitro. All the patients with a history of stroke-like episodes or thrombosis displayed this hypercoagulant phenotype.

CONCLUSION

A thrombin generation assay revealed a hypercoagulant in vitro phenotype under baseline condition; this was accentuated by impaired involvement of the protein C system. This procoagulant phenotype may thus reflect the risk of severe vascular complications. Further research will have to determine whether the thrombin generation assay is predictive of vascular events.

Sex matters: Practice 5P's when treating young women with venous thromboembolism

Sex matters when it comes to venous thromboembolism (VTE). We defined 5P's - period, pill, prognosis, pregnancy, and postthrombotic syndrome - that should be discussed with young women with VTE. Menstrual blood loss (Period) can be aggravated by anticoagulant therapy. This seems particularly true for direct oral anticoagulants. Abnormal uterine bleeding can be managed by hormonal therapy, tranexamic acid, or modification of treatment. The use of combined oral contraceptives (Pill) is a risk factor for VTE. The magnitude of the risk depends on progestagen types and estrogen doses used. In women using therapeutic anticoagulation, concomitant hormonal therapy does not increase the risk of recurrent VTE. Levonorgestrel-releasing intrauterine devices and low-dose progestin-only pills do not increase the risk of VTE. In young women VTE is often provoked by transient hormonal risk factors that affects prognosis. Sex is incorporated as predictor in recurrent VTE risk assessment models. However, current guidelines do not propose using these to guide treatment duration. Pregnancy increases the risk of VTE by 4-fold to 5-fold. Thrombophilia and obstetric risk factors further increase the risk of pregnancy-related VTE. In women with a history of VTE, the risk of recurrence during pregnancy or post partum appears to be influenced by risk factors present during the first VTE. In most women with a history of VTE, antepartum and postpartum thromboprophylaxis with low-molecular-weight heparin is indicated. Women generally are affected by VTE at a younger age then men, and they have to deal with long-term complications (Post-thrombotic syndrome) of deep vein thrombosis early in life.

Antithrombin is incorporated into exosomes produced by antithrombin non-expressing cells

Antithrombin is a serine protease inhibitor that exerts a crucial role in hemostasis as the main inhibitor of the coagulation cascade. It plays also critical roles in other processes, such as inflammation and cancer. Here we show that exosomes released by Madin-Darby canine kidney (MDCK) cells cultured in the presence of heparin incorporate antithrombin from the serum. Exosomal antithrombin is found complexed with the serine protease high temperature requirement A1 (HTRA1), whose cellular levels are increased after serum deprival, the condition used to collect exosomes. Although the biological relevance of the presence of antithrombin in exosomes remains to be investigated, our results suggest a functional interplay between antithrombin and HTRA1.

Trehalose: is it a potential inhibitor of antithrombin polymerization?

SERine Protease INhibitorS (Serpins) are a superfamily of proteins that are characterized by having a similar three-dimensional structure. The native conformation is not most thermodynamically stable, so polymerization is the main consequence when its stability is altered as a result of certain mutations. The polymerization of serpins has been a research topic for many years. Different mechanisms have been proposed and in the same way different compounds or strategies have been studied to prevent polymerization. A recent paper published in Bioscience Reports by Naseem et al. [Biosci. Rep. (2019) 5, 39] studies the role of trehalose in the prevention of the polymerization of antithrombin, which belongs to the serpin superfamily. The main consequence of the antithrombin polymerization is the increased thrombotic risk, since antithrombin is the main inhibitor of the coagulation cascade. The authors demonstrate that trehalose is able to prevent the in vitro polymerization of antithrombin, under conditions in which it usually tends to polymerize, and demonstrate it by using different techniques. However, the binding site of trehalose in antithrombin should be defined by site-directed mutagenesis. On the other hand, it is not clear if all serpins polymerize in vivo through the same mechanism and it is also not clear if the same serpin can even polymerize through different mechanisms. Therefore, there are still doubts about the potential of trehalose or its derivatives to prevent in vivo antithrombin polymerization and, therefore, reduce thrombotic risk, as well as whether trehalose would be able to reduce polymerization in other serpins.

Incidence and features of thrombosis in children with inherited antithrombin deficiency

Pediatric thromboembolism (≤18 years) is very rare (0.07-0.14/10,000/year) but may be more prevalent in children with severe thrombophilia (protein C, protein S or antithrombin deficiency). The aim of this study was to define the prevalence and clinical characteristics of pediatric thrombosis in subjects with inherited antithrombin deficiency. Our observational retrospective multicentric study from two countries recruited 968 patients of any age from 441 unrelated families with genetically, biochemically and functionally characterized antithrombin deficiency. Seventy-three subjects (7.5%) developed thrombosis before 19 years of age. Two high-risk periods for thrombosis were identified: adolescence (12-18 years, n=49) with thrombus localization (lower limb deep venous thrombosis or pulmonary embolism) and triggering factors common to adults (oral contraceptives, surgery or pregnancy); and the neonatal period (<30 days, n=15) with idiopathic thrombosis at unusual sites. The clinical evaluation of pediatric thrombosis in subjects with antithrombin deficiency revealed: i) a high prevalence of cerebral sinovenous thrombosis (n=13, 17.8%), mainly at young age (8 neonates and 4 children <6 years); ii) severe outcome with fatality in six cases (3 neonates, two of them homozygous for p.Leu131Phe). The majority of subjects (76.7%) carried quantitative type I deficiency. This retrospective analysis includes the largest cohort of subjects with inherited antithrombin deficiency so far and provides strong evidence for an increased risk of pediatric thrombosis associated with this thrombophilia (300-fold compared with the general population: 0.41%/year vs. 0.0014%/year, respectively). Our results support testing for antithrombin deficiency in children of affected families, particularly in case of type I deficiency.

Inherited thrombophilia in unprovoked venous thromboembolism: Is non 'O' blood group an additional culprit in Indian patients?

BACKGROUND

Venous thromboembolism (VTE) is a known situation of considerable mortality and morbidity and occurs due to the convergence of multiple acquired and genetic risk factors.

METHODS

In this study, we have comprehensively analyzed the effect of ABO blood groups and inherited thrombophilia factors [Protein C (PC), Protein S (PS), Antithrombin III (AT III), Activated Protein C Resistance (APCR) and Homocysteine (Hcy)] on 150 unprovoked VTE patients, comparing with normal healthy controls. ABO phenotyping was done using gel cards and thrombophilia workup done using standard kits on coagulation autoanalyzer.

RESULTS

Non O blood group was significantly more frequent among cases than controls (77.3% vs. 62.7%) and had higher odds of VTE (OR = 2.03, 95%CI: 1.22-3.37).Positivity for at least one marker of thrombophilia was more in cases (40%) than controls (16%), and led to significantly higher odds (OR = 3.5, 95%CI: 2.03-6.04) of VTE. Deficiency of PS was the commonest thrombophilia abnormality.Combination of non O group with positivity for thrombophilia markers was also more among cases (OR = 5.67, 95%CI: 2.76-11.65). Highest odds of VTE in cases were associated with non O group in combination with increased Homocystein (OR = 10.8, 95%CI: 2.27-51.5).

CONCLUSION

The study results show non O blood group and positivity for factors of inherited thrombophilia in cases impart higher odds of VTE individually. Also combination of both non O blood group and positivity for factors of inherited thrombophilia in cases further increases the odds of VTE. This awareness could assist physicians in identifying those at higher risk of VTE and tailor-made the thromboprophylaxis accordingly.

Thrombophilia, risk factors and prevention

INTRODUCTION

Fifty-three years after the first description of an inherited prothrombotic condition (antithrombin deficiency), our knowledge on hereditary and acquired causes of hypercoagulability that can predispose carriers to venous thromboembolism (VTE) has greatly improved. Areas covered: Main causes of hereditary thrombophilia are summarized alongside new prothrombotic mutations recently discovered. The main causes of acquired thrombophilia, and namely, antiphospholipid antibody syndrome and hyperhomocysteinemia, are also discussed together with other common acquired prothrombotic states characterized by an increase of procoagulant factors and/or a decrease of natural anticoagulants. Finally, suggestions for thromboprophylaxis in carriers of hereditary thrombophilia according to current guidelines/evidence are made for the most challenging high-risk situations (i.e. surgery, pregnancy, contraception, cancer, economy class syndrome) as well as for the prevention of post-thrombotic syndrome. Expert opinion: A carrier of inherited thrombophilia should be evaluated in the framework of other (genetic and/or acquired) coexisting risk factors for first or recurrent VTE when assessing the need and duration of prevention (primary prophylaxis). Prevention strategies should be tailored to each patient and every situational risk factor. The knowledge of the carriership status of severe thrombophilia in the proband can be important to provide asymptomatic relatives with adequate counseling on thrombophilia screening or primary thromboprophylaxis.

Sex, gender and venous thromboembolism: do we care enough?

: The role of sex and gender in determining clinical presentation, diagnostic approach and outcomes of venous thromboembolism is not fully and systematically addressed, except for hormone-related events in women. A lack of knowledge is also apparent regarding drug prescription patterns, physician bias, enrolment in clinical studies and analysis of sex-related confounders in preclinical and clinical studies. As was shown for cardiovascular disease, ignoring sex and gender in medicine can have important impact on outcomes, including mortality. In this review, we seek to address some aspects of venous thromboembolism such as epidemiology and clinical presentation, recurrence, risk factors, animal studies, safety and efficacy of antithrombotic drugs, highlighting what is known and what is not regarding the role of sex and gender, and hoping to focus some interest and to promote the inclusion of these variables in all future studies on venous thromboembolism.

Biochemical and cellular consequences of the antithrombin p.Met1? mutation identified in a severe thrombophilic family

Nature is always the best inspiration for basic research. A family with severe thrombosis and antithrombin deficiency, the strongest anticoagulant, carried a new mutation affecting the translation-start codon of SERPINC1, the gene encoding antithrombin. Expression of this variant in a eukaryotic cell system produced three different antithrombins. Two downstream methionines were used as alternative initiation codons, generating highly expressed small aglycosylated antithrombins with cytoplasmic localization. Wild-type antithrombin was generated by the use of the mutated AUU as initiation codon. Actually, any codon except for the three stop codons might be used to initiate translation in this strong Kozak context. We show unexpected consequences of natural mutations affecting translation-start codons. Downstream alternative initiation AUG codons may be used when the start codon is mutated, generating smaller molecules with potential different cell localization, biochemical features and unexplored consequences. Additionally, our data further support the use of other codons apart from AUG for initiation of translation in eukaryotes.

Fat mass and obesity-associated gene rs9939609 polymorphism is a potential biomarker of recurrent venous thromboembolism in male but not in female patients

Multiple genetic variations have been identified in FTO (fat mass and obesity-associated) gene. Among them, FTO rs9939609 polymorphism is shown to be associated with the risk of primary venous thromboembolism (VTE). However, its role in recurrent VTE is not known. The aim of our study was to investigate the association between FTO rs9939609 polymorphism and the risk of VTE recurrence in a prospective follow-up study in both male and female patients. FTO rs9939609 polymorphism (T/A) was analyzed in the Malmö thrombophilia study (MATS, followed for ~10 years) by using TaqMan PCR. MATS patients (n = 1050) were followed from the discontinuation of anticoagulant treatment until diagnosis of VTE recurrence or the end of follow-up. A total of 126 patients (12%) had VTE recurrence during follow-up. Cox regression analyses showed that sex modified the potential effect of FTO rs9939609 polymorphism on VTE recurrence. Male patients with the AA genotype for the FTO rs9939609 polymorphism had significantly higher risk of VTE recurrence as compared to the TT or AT genotypes (univariate hazard ratio [HR] = 2.05, 95% confidence interval [CI] = 1.2-3.5, P = 0.009 and adjusted HR = 2.03, 95% CI 1.2-3.6, P = 0.013). There was no association between FTO rs9939609 polymorphism and VTE recurrence in female patients. In conclusion, our results show that FTO rs9939609 polymorphism in recurrent VTE may differ according to gender and FTO polymorphism may predict VTE recurrence in male patients.