Factor V Leiden

Genetic factors, risk prediction and AI application of thrombotic diseases

In thrombotic diseases, coagulation, anticoagulation, and fibrinolysis are three key physiological processes that interact to maintain blood in an appropriate state within blood vessels. When these processes become imbalanced, such as excessive coagulation or reduced anticoagulant function, it can lead to the formation of blood clots. Genetic factors play a significant role in the onset of thrombotic diseases and exhibit regional and ethnic variations. The decision of whether to initiate prophylactic anticoagulant therapy is a matter that clinicians must carefully consider, leading to the development of various thrombotic risk assessment scales in clinical practice. Given the considerable heterogeneity in clinical diagnosis and treatment, researchers are exploring the application of artificial intelligence in medicine, including disease prediction, diagnosis, treatment, prevention, and patient management. This paper reviews the research progress on various genetic factors involved in thrombotic diseases, analyzes the advantages and disadvantages of commonly used thrombotic risk assessment scales and the characteristics of ideal scoring scales, and explores the application of artificial intelligence in the medical field, along with its future prospects.

Are all primary omental infarcts truly idiopathic? Five case reports

BACKGROUND

Idiopathic omental infarction (IOI) is challenging to diagnose due to its low incidence and vague symptoms. Its differential diagnosis also poses difficulties because it can mimic many intra-abdominal organ pathologies. Although hypercoagulability and thrombosis are among the causes of omental infarction, venous thromboembolism scanning is rarely performed as an etiological investigation.

CASE SUMMARY

The medical records of the 5 cases, who had the diagnosis of IOI by computed tomography, were examined. The majority of the patients were male (n = 4, 80%) and the mean age was 31 years (range: 21-38). The patients had no previous abdominal surgery or a history of any chronic disease. The main complaint of all patients was persistent abdominal pain. Omental infarction was detected in all patients with contrast-enhanced computed tomography. Conservative treatment was initially preferred in all patients, but it failed in 1 patient (20%). After discharge, all patients were referred to the hematology department for thrombophilia screening. Only 1 patient applied for thrombophilia screening and was homozygous for methylenetetrahydrofolate reductase (A1298C mutation) and heterozygous for a factor V Leiden mutation.

CONCLUSION

IOI should be considered in the differential diagnosis in patients presenting with progressive and/or persistent right side abdominal pain. Investigating risk factors such as hypercoagulability in patients with IOI is also important in preventing future conditions related to venous thromboembolism.

Thrombophilia Screening: Not So Straightforward

Although inherited thrombophilias are lifelong risk factors for a first thrombotic episode, progression to thrombosis is multifactorial and not all individuals with inherited thrombophilia develop thrombosis in their lifetimes. Consequently, indiscriminate screening in patients with idiopathic thrombosis is not recommended, since presence of a thrombophilia does not necessarily predict recurrence or influence management, and testing should be selective. It follows that a decision to undertake laboratory detection of thrombophilia should be aligned with a concerted effort to identify any significant abnormalities, because it will inform patient management. Deficiencies of antithrombin and protein C are rare and usually determined using phenotypic assays assessing biological activities, whereas protein S deficiency (also rare) is commonly detected with antigenic assays for the free form of protein S since available activity assays are considered to lack specificity. In each case, no single phenotypic assay is capable of detecting every deficiency, because the various mutations express different molecular characteristics, rendering thrombophilia screening repertoires employing one assay per potential deficiency, of limited effectiveness. Activated protein C resistance (APCR) is more common than discrete deficiencies of antithrombin, protein C, and protein S and also often detected initially with phenotypic assays; however, some centres perform only genetic analysis for factor V Leiden, as this is responsible for most cases of hereditary APCR, accepting that acquired APCR and rare F5 mutations conferring APCR will go undetected if only factor V Leiden is evaluated. All phenotypic assays have interferences and limitations, which must be factored into decisions about if, and when, to test, and be given consideration in the laboratory during assay performance and interpretation. This review looks in detail at performance and limitations of routine phenotypic thrombophilia assays.

Prevention of thromboembolic events after radical prostatectomy in patients with hereditary thrombophilia due to a factor V Leiden mutation by multidisciplinary coagulation management

Objective

To examine the perioperative impact of factor V Leiden mutation on thromboembolic events' risk in radical prostatectomy (RP) patients. With an incidence of about 5%, factor V Leiden mutation is the most common hereditary hypercoagulability among Caucasians and rarer in Asia. The increased risk of thromboembolic events is three- to seven-fold in heterozygous and to 80-fold in homozygous patients.

Methods

Within our prospectively collected database, we analysed 33 006 prostate cancer patients treated with RP between December 2001 and December 2020. Of those, patients with factor V Leiden mutation were identified. All patients received individualised recommendation of haemostaseologists for perioperative anticoagulation. Thromboembolic complications (deep vein thrombosis and pulmonary embolism) were assessed during hospital stay, as well as according to patient reported outcomes within the first 3 months after RP.

Results

Overall, 85 (0.3%) patients with known factor V Leiden mutation were identified. Median age was 65 (interquartile range: 61-68) years. There was at least one thrombosis in 53 (62.4%) patients and 31 (36.5%) patients had at least one embolic event in their medical history before RP. Within all 85 patients with factor V Leiden mutation, we experienced no thromboembolic complications within the first 3 months after surgery.

Conclusion

In our cohort of patients with factor V Leiden mutation, no thromboembolic events were observed after RP with an individualised perioperative coagulation management concept. This may reassure patients with this hereditary condition who are counselled for RP.

Thrombophilia gene mutations predict venous thromboembolism in ambulatory cancer patients receiving chemotherapy

BACKGROUND

Inherited thrombophilia and cancer both independently increase the risk of venous thromboembolism (VTE). However, whether the increased VTE risk associated with inherited thrombophilia exists in cancer patients is less clear.

OBJECTIVES

Our objective was to determine the influence of inherited thrombophilia on VTE and bleeding risk in moderate-to-high-risk ambulatory cancer patients receiving chemotherapy.

METHODS

We conducted a post hoc analysis using blood samples from patients enrolled in the AVERT trial to determine if previously recognized thrombophilia gene mutations (prothrombin factor [F] II G20210A, FXI, fibrinogen gamma, serpin family A member 10, FV K858R, FXIII, FV Leiden [FVL], and ABO blood) were associated with VTE or bleeding during the 7-months after starting chemotherapy. Logistic regression was used to compare heterozygous and homozygous mutations (combined) to wild-type. VTE rates, bleeding rates, and risk differences for mutations stratified by prophylactic anticoagulation use were calculated.

RESULTS

Of the 447 patients, there were 39 VTE and 39 bleeding events. The odds of VTE were significantly increased with FVL mutation and non-O blood type (odds ratio [OR]: 5.2; 95% CI: 1.9-14.7 and OR: 2.7; 95% CI: 1.2-6.1, respectively). The use of anticoagulation prophylaxis resulted in complete protection in FVL patients, whereas those not receiving anticoagulation had a VTE rate of 119 per 100 patient-years. Lower VTE rates were also observed in non-O blood type patients taking prophylactic anticoagulation. No other thrombophilia genes tested were significantly associated with VTE or bleeding.

CONCLUSION

Our results indicate that FVL mutation and ABO blood type may be important VTE predictors in cancer patients starting chemotherapy.

Inferior Vena Cava Thrombosis in a Patient with Factor V Leiden Syndrome Presenting with Scrotal Pain

Thrombosis in the inferior vena cava (IVC) is a rare but serious condition that can lead to significant morbidity and mortality. We present a case report of a 39-year-old male who presented to the emergency department with right flank pain that had progressed to severe back pain, bilateral flank pain, scrotal pain, and leg pain over the course of two days. The pain was severe enough to affect his daily activities. Laboratory investigations revealed a D-dimer level of 17 ng/mL, creatinine level of 110 µmol/L, and a white blood cell count of 10 × 109/L with a CRP level of 5 mg/L. Urine analysis was positive for blood. Doppler ultrasound of both legs showed deep vein thrombosis extending from the external iliac veins to the distal veins of both legs. Further investigation with computed tomography of the abdomen revealed a large thrombus in the distal vena cava extending to the renal artery and both external and internal iliac veins. The patient was diagnosed with Factor V Leiden syndrome based on genetic testing, which revealed a heterozygous mutation in the F5 gene. He was successfully treated with low molecular weight heparin and warfarin, and after five days of hospitalization, he was discharged with warfarin for long-term anticoagulation. This case report emphasizes the importance of considering IVC thrombosis in patients with a constellation of symptoms, including scrotal pain, and the role of genetic testing in identifying underlying hypercoagulable states.

Unprovoked Venous Thromboembolism: The Search for the Cause

Venous thromboembolism (VTE) is a common vascular disorder encompassing deep vein thrombosis (DVT) and pulmonary embolism (PE). There is no data on global estimates of VTE prevalence and incidence. Most patients with unprovoked VTE require secondary thromboprophylaxis upon the completion of the primary treatment phase if they have no high bleeding risk. Risk prediction models can help identify patients at low VTE recurrence risk who may discontinue anticoagulation upon the completion of the primary treatment phase.

Anti-β2-glycoprotein I and anti-phosphatidylserine/prothrombin antibodies interfere with cleavage of factor V(a) by activated protein C

BACKGROUND

The acquired thrombotic risk factor known as lupus anticoagulant (LA) interferes with laboratory clotting assays and can be caused by autoantibodies against β2-glycoprotein I (β2GPI) and prothrombin. LA is associated with activated protein C (APC) resistance, which might contribute to thrombotic risk in patients with antiphospholipid syndrome. How antibodies against β2GPI and prothrombin cause APC resistance is currently unclear.

OBJECTIVES

To investigate how anti-β2GPI and antiphosphatidylserine/prothrombin (PS/PT) antibodies induce APC resistance.

METHODS

The effects of anti-β2GPI and anti-PS/PT antibodies on APC resistance were studied in plasma (of patients with antiphospholipid syndrome) and with purified coagulation factors and antibodies.

RESULTS

APC resistance was observed in LA-positive patients with anti-β2GPI or anti-PS/PT antibodies and in normal plasma spiked with monoclonal anti-β2GPI or anti-PS/PT antibodies with LA activity. Analysis of factor (F)V cleavage patterns after APC incubation indicated that anti-β2GPI antibodies attenuated APC-mediated FV cleavage at R506 and R306. APC-mediated cleavage at R506 is required for FV cofactor activity during inactivation of FVIIIa. Assays with purified coagulation factors confirmed that anti-β2GPI antibodies interfered with the cofactor function of FV during FVIIIa inactivation but not with FVa inactivation. Anti-PS/PT antibodies attenuated APC-mediated FVa and FVIIIa inactivation. Analysis of FV(a) cleavage patterns after APC incubation indicated that anti-PS/PT antibodies interfere with APC-mediated cleavage of FV at positions R506 and R306.

CONCLUSION

Anti-β2GPI antibodies with LA activity contribute to a procoagulant state by causing APC resistance via interference with the cofactor function of FV during FVIIIa inactivation. LA-causing anti-PS/PT antibodies interfere with the anticoagulant function of APC by preventing FV(a) cleavage.

The Magic of Proteases: From a Procoagulant and Anticoagulant Factor V to an Equitable Treatment of Its Inherited Deficiency

Proteostasis, i.e., the homeostasis of proteins, responsible for ensuring protein turnover, is regulated by proteases, which also participate in the etiopathogenesis of multiple conditions. The magic of proteases is such that, in blood coagulation, one same molecule, such as coagulation factor V, for example, can perform both a procoagulant and an anticoagulant function as a result of the activity of proteases. However, this magic has an insidious side to it, as it may also prevent the completion of the clinical value chain of factor V deficiency. This value chain encompasses the discovery of knowledge, the transfer of this knowledge, and its translation to clinical practice. In the case of rare and ultra-rare diseases like factor V deficiency, this value chain has not been completed as the knowledge acquisition phase has dragged out over time, holding up the transfer of knowledge to clinical practice. The reason for this is related to the small number of patients afflicted with these conditions. As a result, new indications must be found to make the therapies cost-effective. In the case of factor V, significant research efforts have been directed at developing a recombinant factor V capable of resisting the action of the proteases capable of inactivating this factor. This is where bioethics and health equity considerations come into the equation.

The risk of major bleeding in patients with factor V Leiden or prothrombin G20210A gene mutation while on extended anticoagulant treatment for venous thromboembolism

BACKGROUND

Thrombophilia predisposes to venous thromboembolism (VTE) because of acquired or hereditary factors. Among them, it has been suggested that gene mutations of the factor V Leiden (FVL) or prothrombin G20210A mutation (PGM) might reduce the risk of bleeding, but little data exist for patients treated using anticoagulants.

OBJECTIVES

To assess whether thrombophilia is protective against bleeding.

METHODS

This multicentre, multinational, prospective cohort study evaluated adults receiving long-term anticoagulants after a VTE event. We analyzed the incidence of major bleeding as the primary outcome, according to the genotype for FVL and PGM (wild-type and heterozygous/homozygous carriers).

RESULTS

Of 2260 patients with genotype testing, during a median follow-up of 3 years, 106 patients experienced a major bleeding event (17 intracranial and 7 fatal). Among 439 carriers of FVL, 19 experienced major bleeding and there were no differences between any mutation vs wild-type (hazard ratio [HR], 0.89 [0.53-1.49]; p = .66). The comparison of major bleeding events between the 158 patients with any-PGM mutation (heterozygous or homozygous) vs wild-type also showed a nonstatistically significant difference with HR of 0.53 (0.19-1.43), p = .21. However, multivariate analysis demonstrated that major bleeds or clinically relevant nonmajor bleeding were statistically less likely for patients with either FVL and/or PGM compared with patients with both wild-type factor V and prothrombin genes (HR, 0.73; 95% CI = 0.55-0.97; p = .03).

CONCLUSION

This study demonstrates that thrombophilia, defined as the presence of either FVL or the prothrombin G20210A mutation, is related with a lower rate of major/clinically relevant nonmajor bleeding while on anticoagulants in the extended treatment for VTE.

Analysis of 363 Genetic Variants in F5 via an Interactive Web Database Reveals New Insights into FV Deficiency and FV Leiden

The inherited bleeding disorder Factor V (FV) deficiency and clotting risk factor FV Leiden are associated with genetic variants in the F5 gene. FV deficiency occurs with mild, moderate, severe, or asymptomatic phenotypes, and either dysfunctional or reduced amounts of plasma FV protein. Here we present an interactive web database containing 363 unique F5 variants derived from 801 patient records, with 199 FV deficiency-associated variants from 245 patient records. Their occurrence is rationalized based on the 2,224 residue sequence and new FV protein structures. The 199 FV deficiency variants correspond to 26 (13%) mild, 22 (11%) moderate, 49 (25%) severe, 35 (18%) asymptomatic, and 67 (34%) unreported phenotypes. Their variant distributions in the FV domains A1, A2, A3, B, C1 and C2 were 28 (14%), 32 (16%), 34 (17%), 42 (21%), 16 (8%), and 19 variants (10%), respectively, showing that these six regions contain similar proportions of variants. Variants associated with FV deficiency do not cluster near known protein-partner binding sites, thus the molecular mechanism leading to the phenotypes cannot be explained. However, the widespread distribution of FV variants in combination with a high proportion of buried variant residues indicated that FV is susceptible to disruption by small perturbations in its globular structure. Variants located in the disordered B domain also appear to disrupt the FV structure. We discuss how the interactive database provides an online resource that clarifies the clinical understanding of FV deficiency.

A Hypertrophic Spinal Pachymeningitis Patient With Factor V Leiden (G1691A), MTHFR C677T, MTHFR A1298C, PAI-1 4G-5G, Glycoprotein IIIa L33P Gene Mutations

Hypertrophic pachymeningitis (HP) is a rare clinical entity of diverse etiology, characterized by a chronic inflammation that causes dura thickening. Reports of Idiopathic hypertrophic cranial pachymeningitis (IHCP) were related to infections, trauma, tumors, and rheumatologic conditions. It was first described by Charcot and Joffroy regarding spinal meninges in 1869. HP has three stages; progressive radicular symptoms begin first, then muscle weakness and atrophy start. Findings such as paraplegia, loss of bladder and bowel control, and respiratory distress caused by intercostal and diaphragmatic denervation are considered the third stage of the disease. Especially in the cranial form of the disease, nerve ischemia and various cranial neuropathic findings may occur.

Factor V Leiden (G1691A), MTHFR C677T, MTHFR A1298C, and PAI-1 4G-5G gene mutation analysis were measured with an ABI Prism. In this case report, the authors present a case of hypertrophic mutations pachymeningitis with Factor V Leiden (G1691A), MTHFR C677T, MTHFR A1298C, PAI-1 4G-5G, Glycoprotein IIIa L33P gene.

In conclusion, we report a case of HP with Factor V Leiden (G1691A), MTHFR C677T, MTHFR A1298C, PAI-1 4G-5G, and Glycoprotein IIIa L33P gene mutations. We emphasize that the identification of pachymeningitis can be easily bypassed with the application of limited laboratory techniques. As in this case report, we think that these mutations should be analyzed in patients diagnosed with pachymeningitis.

Catheter-Directed Thrombolysis for Acute Digit Ischemia in the Setting of Heterozygous Factor V Leiden Mutation: A Case Report and Review of Literature

CASE

We are reporting the successful treatment of a patient with a heterozygous factor V Leiden mutation who presented with spontaneous thrombotic ischemia of ring and small fingers. Microcatheter-directed administration of thrombolytics at the level of common and proper digital arteries resulted in the salvage of the ring finger to the level of the distal tuft and the entirety of the small finger.

CONCLUSION

Heterozygous factor V Leiden mutation is an extremely unusual etiology for thrombotic digital ischemia. This case report emphasizes the importance of correct diagnosis, timely intervention, and thrombolytic therapy using microcatheters to optimize digital rescue.

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.

The Vascular Endothelium and Coagulation: Homeostasis, Disease, and Treatment, with a Focus on the Von Willebrand Factor and Factors VIII and V

The vascular endothelium has several important functions, including hemostasis. The homeostasis of hemostasis is based on a fine balance between procoagulant and anticoagulant proteins and between fibrinolytic and antifibrinolytic ones. Coagulopathies are characterized by a mutation-induced alteration of the function of certain coagulation factors or by a disturbed balance between the mechanisms responsible for regulating coagulation. Homeostatic therapies consist in replacement and nonreplacement treatments or in the administration of antifibrinolytic agents. Rebalancing products reestablish hemostasis by inhibiting natural anticoagulant pathways. These agents include monoclonal antibodies, such as concizumab and marstacimab, which target the tissue factor pathway inhibitor; interfering RNA therapies, such as fitusiran, which targets antithrombin III; and protease inhibitors, such as serpinPC, which targets active protein C. In cases of thrombophilia (deficiency of protein C, protein S, or factor V Leiden), treatment may consist in direct oral anticoagulants, replacement therapy (plasma or recombinant ADAMTS13) in cases of a congenital deficiency of ADAMTS13, or immunomodulators (prednisone) if the thrombophilia is autoimmune. Monoclonal-antibody-based anti-vWF immunotherapy (caplacizumab) is used in the context of severe thrombophilia, regardless of the cause of the disorder. In cases of disseminated intravascular coagulation, the treatment of choice consists in administration of antifibrinolytics, all-trans-retinoic acid, and recombinant soluble human thrombomodulin.

Venous thrombosis risk factors in pregnant women

Venous thromboembolism (VTE) is the third most common cause of death on Earth after myocardial infarctions and strokes, according to the World Health Organization (WHO). Pregnancy is a unique condition of woman, when enormous changes occur in functioning of the most important systems of homeostasis in a relatively short time. These are physiological hypercoagulation, slowing of blood flow, increase in circulating blood volume, etc. However, while being physiological, these changes increase the risks of venous thromboembolism by almost 6 times. In some cases, there appears an imbalance or dissociation between the functioning of natural antithrombotic systems and the activation of coagulation as a consequence of genetically or acquired determined causes (genetic thrombophilia, antiphospholipid syndrome, comorbidities, obstetric complications and other exogenous and endogenous factors). Accordingly, identification of risk factors, their systematization, and determination of VTE risks in pregnancy and puerperium is one of the most important tasks of clinical medicine. Various recommendations have appeared for practitioners during the last 10-15 years on the basis of the risk factors analysis in order to prevent VTE in pregnant women more effectively. Nevertheless, none of these recommendations can yet take into account all risk factors, although convenient scoring systems have emerged for risk assessment and clear recommendations on anti-thrombotic prophylaxis regimens in risk groups in recent years. This article will review historical understanding of thrombosis in pregnant women, progress in understanding VTE risk factors in pregnant women, and available reserves in identifying new risk factors during pregnancy and puerperium in order to stratify risks more efficiently.

H1299R Variant in Factor V and Recurrent Pregnancy Loss: A Systematic Review and Meta-Analysis Protocol

Recurrent pregnancy loss (RPL) is defined as the loss of two or more pregnancies, affecting approximately 1 to 3% of women worldwide. Scientific data highlight a possible correlation between thrombophilic genetic variants and RPL. H1299R variant in the factor V gene would lead to an increased thrombotic risk associated with frequent miscarriages. However, the data are often conflicting, making this an interesting question for further investigations by evaluating genotype-phenotype correlations to improve the clinical management and genetic counseling of couples. A systematic review and meta-analysis will follow the preferred reporting elements for systematic review and meta-analysis protocols (PRISMA-P). The Pubmed (MEDLINE) and Embase (OVID) databases will be explored to identify suitable articles based on inclusion and exclusion criteria. Inclusion criteria are: (a) H1299R genotyping with clear data reported, referred to as Heterozygous (Het) and/or Homozygous (Hom); (b) articles written in English; (c) analyses of only RPL female patients having at least two or more previous pregnancy losses and compared with a control group. This analysis will present selected scientific evidence, addressing the questions concerning the association between the H1299R variant and RPL, hoping to clarify this still unresolved issue. PROSPERO registration number: CRD42022330077.

The prognostic role of extended preoperative hypercoagulability work-up in high-risk microsurgical free flaps: a single-center retrospective case series of patients with heterozygotic factor V Leiden thrombophilia

INTRODUCTION

Hypercoagulability is associated with an increased risk of microvascular complications and free flap failures. The authors present their experience and approach to diagnosing and treating patients with heterozygotic factor V Leiden (hFVL) thrombophilia undergoing free flap reconstruction.

METHODS

Between November 2009 and June 2018, 23 free flap surgeries were performed in 15 hypercoagulable patients with hFVL. According to the timing of perioperative hypercoagulability work-up, they were grouped into flaps with established diagnoses prior to surgery (Group A) versus flaps with unknown diagnoses prior to surgery (Group B). Baseline characteristics and perioperative complications were compared between both groups, including revision surgeries due to microvascular thromboses, acute bleedings, hematomas, flap necroses, and reconstructive failures.

RESULTS

HFVL mutations had been confirmed preoperatively in 14 free flap surgeries (61%, Group A), whereas in 9 free flap surgeries (39%, Group B), mutations were only diagnosed postoperatively after the occurrence of microvascular thromboses had warranted extended hypercoagulability work-up. The overall rate of intraoperative flap thromboses was 9% (n = 2), whereas the overall rate of postoperative flap thromboses was 43% (n = 10). The corresponding salvage rates were 100% (n = 2/2) for intraoperative and 40% (n = 4/10) for postoperative pedicle thromboses. A total of five free flaps were lost (22%). Upon comparison, flaps with an unconfirmed diagnosis prior to surgery were at ten times higher risk for developing total necroses (flaps lost in Group B = 4/9 versus Group A = 1/14; OR: 10.4; 95% CI 1.0, 134.7; p = 0.03).

CONCLUSION

Meticulous preoperative work-up of patients with any history of hypercoagulability can help reduce free flap loss rates, thus improving surgical outcomes and increasing patient safety.

Frequency of Leiden Mutation in Newborns with Birth Weight below 1500 g

It has been hypothesized that fetal prematurity or Intrauterine Growth Restriction (IUGR) could be related to the presence of factor V of Leiden mutation. This mutation is associated with a higher incidence of pregnancy difficulties that can result in preterm birth. The frequency of Leiden mutation was investigated in the group of newborns with a low birth weight below 1500 g over a six-year period from 2015 to 2020. During this period, 339 newborns were tested, of which 42 newborns with V Leiden mutation (12.4%) were detected. The average of its occurrence frequency in the Czech population was determined as 5.0% based on published studies. In our research, the occurrence of the V Leiden mutation was found significantly higher in newborns under 1500 g. At the same time, we did not demonstrate an increased frequency of births at lower gestational weeks, lower birth weight, or an association with sex in newborns with a positive diagnosis of the Leiden V factor.

Coagulation factor V is a T-cell inhibitor expressed by leukocytes in COVID-19

Clotting Factor V (FV) is primarily synthesized in the liver and when cleaved by thrombin forms pro-coagulant Factor Va (FVa). Using whole blood RNAseq and scRNAseq of peripheral blood mononuclear cells, we find that FV mRNA is expressed in leukocytes, and identify neutrophils, monocytes, and T regulatory cells as sources of increased FV in hospitalized patients with COVID-19. Proteomic analysis confirms increased FV in circulating neutrophils in severe COVID-19, and immunofluorescence microscopy identifies FV in lung-infiltrating leukocytes in COVID-19 lung disease. Increased leukocyte FV expression in severe disease correlates with T-cell lymphopenia. Both plasma-derived and a cleavage resistant recombinant FV, but not thrombin cleaved FVa, suppress T-cell proliferation in vitro. Anticoagulants that reduce FV conversion to FVa, including heparin, may have the unintended consequence of suppressing the adaptive immune system.

Factor V Leiden and the 10-year incidence of depression: A retrospective cohort study conducted in Germany

There is limited literature on the long-term relationship between the diagnosis of factor V Leiden (FVL) and depression. Therefore, the aim of this retrospective cohort study was to investigate the association between FVL and the 10-year incidence of depression in Germany. Patients diagnosed with FVL for the first time in one of 1,274 general practices in Germany between 2000 and 2019 were included in this study (index date). Patients without FVL were matched (1:5) to those with FVL by sex, age, index year, and the average number of consultations per year. In individuals without FVL, index date corresponded to a randomly selected visit date between 2000 and 2019. The association between the diagnosis of FVL and the 10-year incidence of depression was analyzed using Kaplan-Meier curves and Cox regression models. This study included 1,070 patients with and 5,350 patients without FVL (64.9% women; 46.0 [16.5] years). Ten years after the index date, 21.4% and 14.1% of individuals with and without FVL were diagnosed with depression, respectively (log-rank p-value<0.001). After adjusting for thromboembolic events, the Cox regression analysis further showed that FVL was associated with a significant increase in the incidence of depression (HR = 1.61, 95% CI = 1.33-1.95). In this study conducted in Germany, FVL was identified as a long-term risk factor for depression. More research is needed to confirm or refute the present findings in other settings.

A case-control study on factor V Leiden: an independent, gender-dependent risk factor for venous thromboembolism

BACKGROUND

Activated protein C resistance (APCR) due to factor V Leiden (FVL) mutation (R506Q) is a major risk factor in patients with venous thromboembolism (VTE). The present study investigated the clinical manifestations and the risk of venous thromboembolism regarding multiple clinical, laboratory, and demographic properties in FVL patients.

MATERIAL AND METHODS

A retrospective cross-sectional analysis was conducted on a total of 288 FVL patients with VTE according to APCR. In addition, 288 VET control samples, without FVL mutation, were also randomly selected. Demographic information, clinical manifestations, family and treatment history were recorded, and specific tests including t-test, chi-square and uni- and multi-variable regression tests applied.

RESULTS

APCR was found to be 2.3 times significantly more likely in men (OR: 2.1, p < 0.05) than women. The risk of deep vein thrombosis (DVT) and pulmonary embolism (PE) in APCR patients was 4.5 and 3.2 times more than the control group, respectively (p < 0.05). However, APCR could not be an independent risk factor for arterial thrombosis (AT) and pregnancy complications. Moreover, patients were evaluated for thrombophilia panel tests and showed significantly lower protein C and S than the control group and patients without DVT (p < 0.0001).

CONCLUSION

FVL mutation and APCR abnormality are noticeable risk factors for VTE. Screening strategies for FVL mutation in patients undergoing surgery, oral contraceptive medication, and pregnancy cannot be recommended, but a phenotypic test for activated protein C resistance should be endorsed in patients with VTE.

Thrombophilia testing in the era of direct oral anticoagulants

Venous thromboembolism (VTE) is increasingly recognised in primary and secondary care practice. The arrival of direct oral anticoagulants (DOACs) has made the management of VTE easier and more convenient. Some patients established on DOACs may need screening for underlying thrombophilias as certain thrombophilic conditions are known to confer a higher thrombosis risk, although the guidelines for when and how to test for a thrombophilia, especially in a patient taking a DOAC, are unclear. This literature review aims to examine when thrombophilia screening should take place in a patient already taking a DOAC, the effect of DOACs on thrombophilia tests, and analyse whether DOACs are safe and effective in both inherited and acquired thrombophilias.

Laboratory testing for activated protein C resistance: rivaroxaban induced interference and a comparative evaluation of andexanet alfa and DOAC Stop to neutralise interference

Background Investigation of hemostasis is problematic when patients are on anticoagulant therapy. Rivaroxaban especially causes substantial interference, extending many clot-based tests, thereby leading to false positive or negative events. In particular, rivaroxaban affects some assays for activated protein C resistance (APCR). Methods We assessed, in an international setting, cross laboratory (n = 31) testing using four samples to evaluate rivaroxaban induced interference in APCR testing, and whether this interference could be neutralised. The samples comprised: (A) pool of normal plasma (APCR-negative control); (B) this normal pool spiked with rivaroxaban (200 ng/mL) to create rivaroxaban-induced interference (potential 'false' positive APCR event sample); (C) the rivaroxaban sample subsequently treated with a commercial direct oral anticoagulant 'DOAC-neutraliser' (DOAC Stop), or (D) treated with andexanet alfa (200 μg/mL). Testing was performed blind to sample type. Results The rivaroxaban-spiked sample generated false positive APCR results for some, but unexpectedly not most APCR-tests. The sample treated with DOAC Stop evidenced a correction in the rivaroxaban-affected APCR assays, and did not otherwise adversely affect the rivaroxaban 'unaffected' APCR assays. The andexanet alfa-treated sample did not evidence correction of the false positive APCR, and instead unexpectedly exacerbated false positive APCR status with many tests. Conclusions DOAC Stop was able to neutralise any APCR interference induced by rivaroxaban. In contrast, andexanet alfa did not negate such interference, and instead unexpectedly created more false-positive APCR events.

Vaccine-induced immune thrombotic thrombocytopenia after vaccination against Covid-19: A clinical dilemma for clinicians and patients

The coronavirus disease 2019 (Covid-19) pandemic has had devastating effects on public health worldwide, but the deployment of vaccines for Covid-19 protection has helped control the spread of SARS Coronavirus 2 (SARS-CoV-2) infection where they are available. The common side effects reported following Covid-19 vaccination were mostly self-restricted local reactions that resolved quickly. Nevertheless, rare vaccine-induced immune thrombotic thrombocytopenia (VITT) cases have been reported in some people being vaccinated against Covid-19. This review summarizes the thromboembolic events after Covid-19 vaccination and discusses its molecular mechanism, incidence rate, clinical manifestations and differential diagnosis. Then, a step-by-step algorithm for diagnosing such events, along with a management plan, are presented. In conclusion, considering the likeliness of acquiring severe SARS-CoV-2 infection and its subsequent morbidity and mortality, the benefits of vaccination outweigh its risks. Hence, if not already initiated, all governments should begin an effective and fast public vaccination plan to overcome this pandemic.

Cases in Precision Medicine: Genetic Testing to Predict Future Risk for Disease in a Healthy Patient

Genetic testing is performed more routinely in clinical practice, and direct-to-consumer tests are widely available. It has obvious appeal as a preventive health measure. Clinicians and their healthy patients increasingly inquire about genetic testing as a tool for predicting diseases, such as cancer, heart disease, or dementia. Despite demonstrated utility for diagnosis in the setting of many diseases, genetic testing still has many limitations as a predictive tool for healthy persons. This article uses a hypothetical case to review key considerations for predictive genetic testing.

A genome-wide meta-analysis yields 46 new loci associating with biomarkers of iron homeostasis

Iron is essential for many biological functions and iron deficiency and overload have major health implications. We performed a meta-analysis of three genome-wide association studies from Iceland, the UK and Denmark of blood levels of ferritin (N = 246,139), total iron binding capacity (N = 135,430), iron (N = 163,511) and transferrin saturation (N = 131,471). We found 62 independent sequence variants associating with iron homeostasis parameters at 56 loci, including 46 novel loci. Variants at DUOX2, F5, SLC11A2 and TMPRSS6 associate with iron deficiency anemia, while variants at TF, HFE, TFR2 and TMPRSS6 associate with iron overload. A HBS1L-MYB intergenic region variant associates both with increased risk of iron overload and reduced risk of iron deficiency anemia. The DUOX2 missense variant is present in 14% of the population, associates with all iron homeostasis biomarkers, and increases the risk of iron deficiency anemia by 29%. The associations implicate proteins contributing to the main physiological processes involved in iron homeostasis: iron sensing and storage, inflammation, absorption of iron from the gut, iron recycling, erythropoiesis and bleeding/menstruation.

Apixaban Does Not Interfere With Protein S or Activated Protein C Resistance (Factor V Leiden) Testing Using aPTT-Based Methods

CONTEXT.—

Apixaban causes a false increase in activated protein C resistance (APCR) ratios and possibly protein S activity.

OBJECTIVE.—

To investigate whether this increase can mask a diagnosis of factor V Leiden (FVL) or protein S deficiency in an actual population of patients undergoing apixaban treatment and hypercoagulation testing.

DESIGN.—

During a 4.5-year period involving 58 patients, we compared the following 4 groups: heterozygous for FVL (FVL-HET)/taking apixaban, wild-type/taking apixaban, heterozygous for FVL/no apixaban, and normal APCR/no apixaban. Patients taking apixaban were also tested for protein S functional activity and free antigen (n = 40).

RESULTS.—

FVL-HET patients taking apixaban had lower APCR ratios than wild-type patients (P < .001). Activated protein C resistance in FVL-HET patients taking apixaban fell more than 3 SD below the cutoff of 2.2 at which the laboratory reflexes FVL DNA testing. No cases of FVL were missed despite apixaban. In contrast to rivaroxaban, apixaban did not interfere with the assessment of protein S activity (mean activity 93.9 IU/dL, free antigen 93.1 IU/dL, P = .39). A total of 3 of 40 patients (8%) had low free protein S antigen (30, 55, and 57 IU/dL), with correspondingly similar activity results (27, 59, and 52 IU/dL, respectively). Apixaban did not cause a missed diagnosis of protein S deficiency.

CONCLUSIONS.—

Despite apixaban treatment, APCR testing can distinguish FVL-HET from healthy patients, rendering indiscriminate FVL DNA testing of all patients on apixaban unnecessary. Apixaban did not affect protein S activity.

Genetic Factors in Antiphospholipid Syndrome: Preliminary Experience with Whole Exome Sequencing

As in many autoimmune diseases, the pathogenesis of the antiphospholipid syndrome (APS) is the result of a complex interplay between predisposing genes and triggering environmental factors, leading to a loss of self-tolerance and immune-mediated tissue damage. While the first genetic studies in APS focused primarily on the human leukocytes antigen system (HLA) region, more recent data highlighted the role of other genes in APS susceptibility, including those involved in the immune response and in the hemostatic process. In order to join this intriguing debate, we analyzed the single-nucleotide polymorphisms (SNPs) derived from the whole exome sequencing (WES) of two siblings affected by APS and compared our findings with the available literature. We identified genes encoding proteins involved in the hemostatic process, the immune response, and the phospholipid metabolism (PLA2G6, HSPG2, BCL3, ZFAT, ATP2B2, CRTC3, and ADCY3) of potential interest when debating the pathogenesis of the syndrome. The study of the selected SNPs in a larger cohort of APS patients and the integration of WES results with the network-based approaches will help decipher the genetic risk factors involved in the diverse clinical features of APS.

Limitations of a calibrated, quantitative APC-R assay under routine conditions

INTRODUCTION

The aim of this study was to evaluate the Hemoclot Quanti. V-L assay in various clinical conditions.

METHODS

We compared the Hemoclot Quanti.V-L assay with DNA testing and with the Pefakit assay in 60 normal (no mutation) vs carriers of the factor V (FV) Leiden mutation (56 heterozygous and three homozygous). We further investigated the interference of lupus anticoagulant on test results in normal and heterozygous individuals and of direct oral anticoagulants (DOACs) at trough and peak levels. Additionally, DOAC-Remove was tested in samples containing DOACs at peak levels. We further evaluated the influence of FV deficiency on this quantitative assay.

RESULTS

There was a 100% agreement between the Quant. V-L assay and DNA testing in 60 normal individuals. However, 1.85% of heterozygous and 33% of homozygous samples were falsely classified with the quantitative assay, and no misclassification was observed with the Pefakit assay. Lupus anticoagulant did not influence the test results of the quantitative assay. DOACs also interfered with test results in heterozygous patients, but this effect was prevented with the DOAC-Remove procedure. Even mild FV deficiency affected the test results of the quantitative assay in heterozygous patients leading either to misclassification or the need for subsequent PCR testing.

CONCLUSION

The quantitative FV-L assay has several limitations, especially FV deficiency and the presence of DOACs have to be ruled out before running this quantitative assay.

Venous thrombosis risk factors in pregnant women

OBJECTIVES

Assess all risk factors of venous thromboembolism (VTE) in pregnancy and puerperium.

METHODS

Different guidelines for VTE prevention have been analyzed.

RESULTS

Various recommendations have appeared for practitioners during the last 10-15 years on the basis of the risk factors analysis in order to prevent VTE in pregnant women more effectively. Nevertheless, none of these recommendations can yet take into account all risk factors, although convenient scoring systems have emerged for risk assessment and clear recommendations on anti-thrombotic prophylaxis regimens in risk groups in recent years.

CONCLUSIONS

VTE is the third most common cause of death on Earth after myocardial infarctions and strokes, according to the World Health Organization. Pregnancy is a unique condition of woman, when enormous changes occur in functioning of the most important systems of homeostasis in a relatively short time. These are physiological hypercoagulation, slowing of blood flow, increase in circulating blood volume, etc. However, while being physiological, these changes increase the risks of venous thromboembolism by almost six times. In some cases, there appears an imbalance or dissociation between the functioning of natural antithrombotic systems and the activation of coagulation as a consequence of genetically or acquired determined causes (genetic thrombophilia, antiphospholipid syndrome, comorbidities, obstetric complications and other exogenous and endogenous factors). Accordingly, identification of risk factors, their systematization, and determination of VTE risks in pregnancy and puerperium is one of the most important tasks of clinical medicine. This article will review historical understanding of thrombosis in pregnant women, progress in understanding VTE risk factors in pregnant women, and available reserves in identifying new risk factors during pregnancy and puerperium in order to stratify risks more efficiently.

ARMS TaqMan real-time PCR for genotyping factor V Leiden mutation in Han Chinese

Factor V Leiden (FV_Leiden ) is a missense mutation of 1691 position (G1691A) in exon 10 of FV gene, and being a genetic risk for venous thrombosis. Currently, there are several PCR-based methods for detecting FV_Leiden mutation; however, these methods have disadvantages such as time-consuming, cumbersome steps and potentially hazardous gels. The aims of present study were to develop a simple, time-saving, accurate, and gel-free method, called amplification refractory mutation system (ARMS) TaqMan real-time PCR, for detecting FV_Leiden mutation. We severally designed two specific reverse primers for mutant and wild-type through intentional introduction of mismatched nucleotide at the penultimate 3' position. Although target amplicon amplification efficiency is reduced, but another corresponding amplicon is almost completely inhibited. Then, specific TaqMan-probe was designed to detect target amplicon. Established method was used to detect 500 unselected samples in Han Chinese, the results showed 499 cases of wild-type and one heterozygote. Afterward, 50 randomly picked wild-type cases and one heterozygote were reexamined by bidirectional DNA sequencing, which is considered as "Gold standard method." Exhilaratingly, the results detected by the two methods were completely consistent. At last, allelic frequency of FV_Leiden was calculated the in Han Chinese. Given the above results, A FV_Leiden heterozygote has been found in 500 random samples in Han Chinese, and the allelic frequency was 0.1%. In conclusion, the ARMS TaqMan real-time PCR is an ideal detecting system for genotyping FV_Leiden mutation in clinical application, and FV_Leiden mutation exists in Han Chinese despite extremely low prevalence.

Successful Digital Revascularization in a Patient With Factor V Leiden Mutation

Replantation/revascularization involves microsurgical anastomosis of the digital arteries and veins, which are often 2 mm or less in diameter. Thrombosis is a known risk of revascularization that ultimately can lead to ischemic digital loss. Factor V Leiden mutation is present in 3% to 8% of the population and results in generalized hypercoagulability. We present the case of a single-digit revascularization that was successful following vein grafting in a patient with factor V Leiden mutation.

Venous Thrombosis and Hypercoagulability in the Abdomen and Pelvis: Causes and Imaging Findings

Venous thromboembolism (VTE), which includes deep venous thrombosis and pulmonary embolism, is a significant cause of morbidity and mortality. In recent decades, US, CT, and MRI have surpassed catheter-based angiography as the imaging examinations of choice for evaluation of vascular structures and identification of thrombus owing to their ready availability, noninvasive nature, and, in the cases of US and MRI, lack of exposure to ionizing radiation. As a result, VTE and associated complications are commonly identified in day-to-day radiologic practice across a variety of clinical settings. A wide range of hereditary and acquired conditions can increase the risk for development of venous thrombosis, and many patients with these conditions may undergo imaging for unrelated reasons, leading to the incidental detection of VTE or one of the associated complications. Although the development of VTE may be an isolated occurrence, the imaging findings, in conjunction with the clinical history and vascular risk factors, may indicate a predisposing condition or underlying diagnosis. Furthermore, awareness of the many clinical conditions that result in an increased risk of venous thrombosis may aid in detection of thrombus and any concomitant complications. For these reasons, it is important that practicing radiologists be familiar with the multimodality imaging findings of thrombosis, understand the spectrum of diseases that contribute to the development of thrombosis, and recognize the potential complications of hypercoagulable states and venous thrombosis. Online DICOM image stacks and supplemental material are available for this article. ^©RSNA, 2020.

The association between activated protein C ratio and Factor V Leiden are gender-dependent

Background The most common cause of activated protein C (aPC) resistance is a missense substitution (Arg506Gln), known as Factor V Leiden (FVL). Due to its low cost, many laboratories use the aPC ratio as a primary test with a unisex cut-off. However, the association between the aPC ratio and FVL including any relation to gender has been sparsely investigated. Methods Results of the aPC ratio and FVL analyses from 1081 patients referred to the Thrombophilia Clinic at Odense University Hospital were compared. Results In 153 FVL positive patients, the mean aPC ratio was 2.1 ± 0.3, which differed from 2.7 ± 0.4 in FVL negative individuals (p < 0.01). The receiver operating characteristics (ROC), with area under the curve (AUC) of 0.93, indicated the optimal aPC cut-off at 2.3-2.4, with sensitivity 89%-94%, specificity 71%-84%, positive predictive value 35%-48% and negative predictive value 98%-99%. In FVL positive females, the mean aPC ratio was 2.0 ± 0.3, which differed from males (2.1 ± 0.3, p < 0.05). In FVL negative females, the mean aPC ratio was 2.6 ± 0.4, also different from males (2.8 ± 0.5, p < 0.01). Of note, 35% of FVL negative females had an aPC ratio ≤2.4 against 18% in males (p < 0.01). Conclusions Our results indicate that the aPC ratio is lower in females than in males. Due to a high negative predictive value the aPC ratio can be used as a first line test for FVL, but those found positive must be confirmed with a DNA test.

Clotting factors: Clinical biochemistry and their roles as plasma enzymes

The purpose of this review is to describe structure and function of the multiple proteins of the coagulation system and their subcomponent domains. Coagulation is the process by which flowing liquid blood plasma is converted to a soft, viscous gel entrapping the cellular components of blood including red cells and platelets and thereby preventing extravasation of blood. This process is triggered by the minimal proteolysis of plasma fibrinogen. This transforms the latter to sticky fibrin monomers which polymerize into a network. The proteolysis of fibrinogen is a function of the trypsin-like enzyme termed thrombin. Thrombin in turn is activated by a cascade of trypsin-like enzymes that we term coagulation factors. In this review we examine the mechanics of the coagulation cascade with a view to the structure-function relationships of the proteins. We also note that two of the factors have no trypsin like protease domain but are essential cofactors or catalysts for the proteases. This review does not discuss the major role of platelets except to highlight their membrane function with respect to the factors. Coagulation testing is a major part of routine diagnostic clinical pathology. Testing is performed on specimens from individuals either with bleeding or with thrombotic disorders and those on anticoagulant medications. We examine the basic in-vitro laboratory coagulation tests and review the literature comparing the in vitro and in vivo processes. In vitro clinical testing typically utilizes plasma specimens and non-physiological or supraphysiological activators. Because the review focuses on coagulation factor structure, a brief overview of the evolutionary origins of the coagulation system is included.

DOAC-Remove abolishes the effect of direct oral anticoagulants on activated protein C resistance testing in real-life venous thromboembolism patients

Background

Direct oral anticoagulants (DOACs) may cause false results of activated protein C resistance (APC-R) ratio. DOAC-Remove, a new reagent based on activated carbon, has been designed to eliminate the interference of DOACs on coagulation assays. The aim of the study was to investigate whether the use of DOAC-Remove enables to determine APC-R in patients treated with DOACs.

Methods

We assessed 74 venous thromboembolism (VTE) patients, including 25 on rivaroxaban, 25 on apixaban and 24 taking dabigatran. APC-R was determined using the Russell Viper Venom Time (RVVT)-based clotting test. APC-R and DOAC concentrations were tested at baseline and following DOAC-Remove. Thrombophilia, including factor V Leiden (FVL) mutation was tested.

Results

FVL mutation was found in 20 (27%) patients. The APC-R ratio at baseline was measurable in 43 patients (58.1%), including 20 (80%) on rivaroxaban, 19 (76%) on apixaban and four (16.7%) on dabigatran. In patients with measurable APC-R at baseline, the ratio >2.9 was found in 23 patients (53.5%). In 16 (37.2%) subjects APC-R ratio <1.8 suggested FVL mutation which was genetically confirmed. Four (9.3%) FVL carriers on dabigatran showed negative/equivocal APC-R results. In 11 (14.9%) patients taking rivaroxaban or apixaban, in whom blood was collected 2–5 h since the last dose, we observed unmeasurable APC-R. DOAC-Remove almost completely eliminated all plasma DOACs. After addition of DOAC-Remove all APC-R ratios were measurable. In four FVL carriers on dabigatran with false negative APC-R, DOAC-Remove resulted in APC-R ratios <1.8.

Conclusions

DOAC-Remove effectively reduces DOACs concentration in plasma, which enables FVL testing using APC-R.

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.

Genetic susceptibility to cerebrovascular disease: A systematic review

Investigation of genetic susceptibility to cerebrovascular disease has been of growing interest. A systematic review of human studies assessing neurogenomic aspects of cerebrovascular disease was performed according to the preferred reporting items for systematic reviews and meta-analyses (PRISMA) statement. Any association study exploring genetic variants located in the exome associated with one of the major cerebrovascular diseases with at least 500 subjects was eligible for inclusion. Of 6874 manuscripts identified, 35 studies met the inclusion criteria. Most studies of interest focused on ischemic stroke and cerebrovascular occlusive disease. Large cohort genetic association studies on hemorrhagic cerebrovascular disease were less common. In addition to rare, well-established monogenic conditions with significant risk for cerebrovascular disease, a number of genetic variants are also relevant to cerebrovascular pathogenesis as part of a multifactorial process. The 45 polymorphisms identified were located in genes involved in processes related to endothelial and vascular health (15 (33.4%) variants), plasma lipid metabolism (10 (22.2%) variants), inflammation (9 (20%) variants), coagulation (3 (6.7%) variants), and blood pressure modulation (2 (4.4%) variants), and other (6 (13.3%) variants). This work represents a comprehensive overview of genetic variants in the exome relevant to ischemic and hemorrhagic stroke pathophysiology.

Coagulation, Microenvironment and Liver Fibrosis

Fibrosis is the main consequence of any kind of chronic liver damage. Coagulation and thrombin generation are crucial in the physiological response to tissue injury; however, the inappropriate and uncontrolled activation of coagulation cascade may lead to fibrosis development due to the involvement of several cellular types and biochemical pathways in response to thrombin generation. In the liver, hepatic stellate cells and sinusoidal endothelial cells orchestrate fibrogenic response to chronic damage. Thrombin interacts with these cytotypes mainly through protease-activated receptors (PARs), which are expressed by endothelium, platelets and hepatic stellate cells. This review focuses on the impact of coagulation in liver fibrogenesis, describes receptors and pathways involved and explores the potential antifibrotic properties of drugs active in hemostasis in studies with cells, animal models of liver damage and humans.

Activated protein C resistance in patients following venous thromboembolism receiving rivaroxaban versus vitamin K antagonists: assessment using Russell viper venom time-based assay

: Activated protein C resistance (APC-R) is assessed as part of thrombophilia screening, preferably in patients not taking oral anticoagulants. Rivaroxaban is known to alter some APC-R assays. To our knowledge, there have been no reports on the effect of rivaroxaban on the Russell viper venom time (RVVT)-based APC-R assay in real-life patients. In 168 consecutive outpatients suspected of having venous thromboembolism because of thrombophilia, APC-R was determined using the RVVT-based ProC Ac R assay (Siemens, Marburg, Germany). Patients receiving rivaroxaban or vitamin K antagonists were eligible. We measured rivaroxaban concentrations using the anti-Xa Biophen DiXal assay (Hyphen Biomed, Neuville-Sur-Oise, France) and factor V Leiden using the real-time PCR. APC-R was detected in 23 (28%) patients on rivaroxaban (n = 81) administrated 2-48 h since the blood draw, 15 (28%) patients on vitamin K antagonists (n = 54), and in four (12%) patients off anticoagulation (n = 33). Compared with nonanticoagulated patients, APC-R ratios were similar in patients on rivaroxaban, without any correlation with rivaroxaban concentrations (from 0 to 303 μg/l). None of the patients on rivaroxaban were found to have false-negative or false-positive APC-R ratios. Rivaroxaban concentrations up to 300 μg/l do not affect results of the ProC Ac R RVVT-based assay, which could be recommended in patients referred to a clinic for thrombophilia screening in whom the time since the last dose of rivaroxaban is uncertain.

Factor V Leiden paradox in a middle-aged Swedish population: A prospective study

Few prospective studies have examined the factor V paradox: factor V Leiden (FVL) is a stronger risk factor for deep venous thrombosis (DVT) than for pulmonary embolism (PE). The present study, to the best of our knowledge, is the first population-based study aimed to examine the relationship between FVL and incidence of venous thromboembolism (VTE), DVT and PE in a prospective cohort study of middle-aged Swedish individuals. FVL was determined in 4890 subjects (aged 46–68 years, 57% women) from the general population without previous VTE or cancer, who participated in the Malmö Diet and Cancer study between 1991 and 1994. Incident cases of VTE were identified from the Swedish patient register during a mean follow-up of 15.6 years. Of 4890 subjects with determination of FVL (10.2% carriers), 220 had VTE during follow-up (113 DVT, 78 PE, 29 both). Incidence of VTE was significantly higher in subjects with heterozygous and homozygous FVL: adjusted hazard ratios (HR) were 1.8 (95% CI 1.3–2.6, p=0.001) and 6.5 (2.1–21, p=0.001), respectively. The population attributable fraction was 8.7% for FVL. Adjusted HRs for DVT were 2.2 (1.4–3.3, p<0.001) for heterozygotes and 3.3 (0.5–24, p=0.233) for homozygotes. Adjusted HRs for PE were 1.2 (0.65–2.2, p=0.582) for heterozygotes and 8.7 (2.1–36, p=0.003) for homozygotes. The FVL paradox was confirmed for heterozygotes for FVL. However, homozygotes for FVL had a high risk for PE, suggesting that the FVL paradox is related to the carriership of one wild type and one mutated factor V allele.

Laboratory assessment of Activated Protein C Resistance/Factor V-Leiden and performance characteristics of a new quantitative assay

Activated Protein C Resistance is mainly associated to a factor V mutation (RQ506), which induces a deficient inactivation of activated factor V by activated protein C, and is associated to an increased risk of venous and arterial thrombosis in affected individuals, caused by the prolonged activated factor V survival. Its prevalence is mainly in Caucasians (about 5%), and this mutation is absent in Africans and Asians. Presence of Factor V-Leiden is usually evidenced with clotting methods, using a two-step APTT assay performed without or with APC: prolongation of blood coagulation time is decreased if this factor is present. The R506Q Factor V-Leiden mutation is now usually characterized using molecular biology, and this technique tends to become the first intention assay for characterization of patients. Both techniques are qualitative, and allow classifying tested individuals as heterozygotes or homozygotes for the mutation, when present. A new quantitative assay for Factor V-Leiden, using a one-step clotting method, has been developed, and designed with highly purified human coagulation proteins. Clotting is triggered with human Factor Xa, in presence of calcium and phospholipids (mixture which favours APC action over clotting process). Diluted tested plasma, is supplemented with a clotting mixture containing human fibrinogen, prothrombin, and protein S at a constant concentration. APC is added, and clotting is initiated with calcium. Calibration is performed with a pool of plasmas from patients carrying the R506Q Factor V mutation, and its mixtures with normal plasma. Homozygous patients have clotting times of about <40sec; heterozygous patients have clotting times of about 40-60sec and normal individuals yield clotting times >70sec. Factor V-Leiden concentration is usually >75% in homozygous patients, 30-60% in heterozygous patients and below 5% in normal. The assay is insensitive to clotting factor deficiencies (II, VII, VIII: C, IX, X), dicoumarol or heparin therapies, and has no interference with lupus anticoagulant (LA). This new assay for Factor V-Leiden can be easily used in any coagulation laboratory, is performed as a single test, and is quantitative. This assay has a high robustness, is accurate and presents a good intra- (<3%) and inter-assay (<5%) variability. It contributes solving most of the laboratory issues faced when testing factor V-Leiden. Quantitation of Factor V-L could contribute to a better assessment of thrombotic risk in affected patients, as this complication is first associated to and caused by the presence of a defined amount of FVa.

Panton-Valentine Leukocidin Producing Staphylococcus Aureus Facial Pyomyositis Causing Partial Cavernous Sinus Thrombosis

We present a case of subtotal cavernous sinus thrombosis secondary to Panton-Valentine leukocidin-associated Staphylococcus aureus pyomyositis of the muscles of mastication in a previously healthy child, who was successfully managed with no residual disease. He was found to have a factor V Leiden heterozygous mutation. We highlight the propensity of Panton-Valentine leukocidin Staphylococcus aureus to induce venous thrombosis at any site but with potential for more severe consequences in the head. We highlight pyomyositis as a differential for periorbital cellulitis and discuss the significance of the factor V Leiden mutation.

Factor V G1691A is associated with an increased risk of retinal vein occlusion: a meta-analysis

We performed a meta-analysis to investigate the association between the Factor V G1691A polymorphism and the risk of retinal vein occlusion (RVO). This analysis included 37 studies involving 2,510 cases and 3,466 controls. Factor V G1691A was associated with an increased risk of RVO in the allele, heterozygote, dominant, and carrier models (PA < 0.001, odds ratios >1), but not the homozygote or recessive models (PA > 0.05). Similar results were observed in a meta-analysis of central retinal vein occlusion (CRVO) and when comparing Caucasian subgroups to population-based controls. These data demonstrate that the G/A genotype of Factor V G1691A is associated with an increased risk of RVO/CRVO in a Caucasian population.

Rivaroxaban Causes Missed Diagnosis of Protein S Deficiency but Not of Activated Protein C Resistance (Factor V Leiden)

Context.—

Rivaroxaban causes a false increase in activated protein C resistance (APCR) ratios and protein S activity.

Objective.—

To investigate whether this increase masks a diagnosis of factor V Leiden (FVL) or protein S deficiency in a “real-world” population of patients undergoing rivaroxaban treatment and hypercoagulation testing.

Design.—

During a 2.5-year period, we compared 4 groups of patients (n = 60): FVL heterozygous (FVL-HET)/taking rivaroxaban, wild-type/taking rivaroxaban, FVL-HET/no rivaroxaban, and normal APCR/no rivaroxaban. Patients taking rivaroxaban were tested for protein S functional activity and free antigen (n = 32).

Results.—

The FVL-HET patients taking rivaroxaban had lower APCR ratios than wild-type patients (P &lt; .001). For FVL-HET patients taking rivaroxaban, mean APCR was 1.75 ± 0.12, versus 1.64 ± 0.3 in FVL-HET patients not taking rivaroxaban (P = .005). Activated protein C resistance in FVL-HET patients fell more than 3 SDs below the cutoff of 2.2 at which the laboratory reflexes FVL DNA testing. No cases of FVL were missed despite rivaroxaban. In contrast, rivaroxaban falsely elevated functional protein S activity, regardless of the presence or absence of FVL (P &lt; .001). A total of 4 of 32 patients (12.5%) had low free protein S antigen (range, 58%–67%), whereas their functional protein S activity appeared normal (range 75%–130%). Rivaroxaban would have caused a missed diagnosis of all cases of protein S deficiency during the study if testing relied on the protein S activity assay alone.

Conclusions.—

Despite rivaroxaban treatment, APCR testing can distinguish FVL-HET from normal patients, rendering indiscriminate FVL DNA testing of all patients on rivaroxaban unnecessary. Free protein S should be tested in patients taking rivaroxaban to exclude hereditary protein S deficiency.

Targeting activated protein C to treat hemophilia

PURPOSE OF REVIEW

Hemophilia is a debilitating disease, marked by frequent, painful bleeding events, joint deterioration and early death. All current treatments consist of i.v. infusions of replacement factor or other procoagulant factors, and are incompletely effective, due in part to the short half-lives of the proteins. An alternative approach is to rebalance hemostasis by inhibiting natural anticoagulant mechanisms. In this article, we explain why activated protein C (APC) is an appropriate and safe target for the treatment of hemophilia.

RECENT FINDINGS

A serpin (serine protease inhibitor) was engineered to specifically inhibit APC and was found to rescue hemostasis in a hemophilia mouse model, even after a severe tail clip injury. However, APC is also anti-inflammatory and has cytoprotective activities, raising safety concerns over the use of an APC inhibitor to treat hemophilia. We summarize the molecular basis of the anticoagulant and signaling activities of APC to assess the potential impact of targeting APC.

SUMMARY

We conclude that the signaling and anticoagulant functions of APC are in spatially and kinetically distinct compartments, and that it is possible to specifically inhibit the anticoagulant activity of APC. Targeting APC with a serpin is remarkably effective and may be safe for long-term prophylactic use in the treatment of hemophilia.