High long-term absolute risk of recurrent venous thromboembolism in patients with hereditary deficiencies of protein S, protein C or antithrombin

A Comprehensive Review of Risk Factors and Thrombophilia Evaluation in Venous Thromboembolism

Venous thromboembolism (VTE), which encompasses deep vein thrombosis (DVT) and pulmonary embolism (PE), is a significant cause of morbidity and mortality worldwide. There are many factors, both acquired and inherited, known to increase the risk of VTE. Most of these result in increased risk via several common mechanisms including circulatory stasis, endothelial damage, or increased hypercoagulability. Overall, a risk factor can be identified in the majority of patients with VTE; however, not all risk factors carry the same predictive value. It is important for clinicians to understand the potency of each individual risk factor when managing patients who have a VTE or are at risk of developing VTE. With this, many providers consider performing a thrombophilia evaluation to further define a patient's risk. However, guidance on who to test and when to test is controversial and not always clear. This comprehensive review attempts to address these aspects/concerns by providing an overview of the multifaceted risk factors associated with VTE as well as examining the role of performing a thrombophilia evaluation, including the indications and timing of performing such an evaluation.

A Scoring System to Determine the Risk Factors Causing Recurrent Pulmonary Thromboembolism

BACKGROUND

The risk of recurrence in pulmonary embolism is the highest in the first week after the acute event. Although it decreases over time, it may remain high for months depending on compliance with treatment and the nature of the underlying risk factor. Our study aimed to identify risk factors that lead to recurrence in pulmonary thromboembolism (PTE) patients and establish an easy-to-use scoring system that determines the risk of recurrence after the first embolism.

METHODS

We retrospectively evaluated 1452 patients who were diagnosed with acute PTE between 7/1/2014 and 7/1/2019. Demographic data, comorbidities and clinical data of the patients, and risk factors were recorded. The relationship of the examined parameters with recurrent PTE was evaluated.

RESULTS

Diabetes mellitus (DM), hypertension, obesity, and the presence of at least one hereditary risk factor were found to be associated with recurrence. The sensitivity of our score was 66.9%, the specificity was 63.2%, the positive predictive value was 19%, and the negative predictive value was 93.7%. The risk of recurrence in the patients identified as high-risk in the scoring system was 3.47 times higher than those identified as low-risk.

CONCLUSION

In terms of risk of recurrence, special attention should be paid to patients with diabetes, HT, obesity and any of the hereditary risk factors. Using scoring systems to determine the risk of recurrence will be valuable and interesting as it is easy-to-use, gives quick results and provides quantitative results.

Gene editing of human iPSCs rescues thrombophilia in hereditary antithrombin deficiency in mice

Hereditary antithrombin deficiency is caused by SERPINC1 gene mutations and predisposes to recurrent venous thromboembolism that can be life-threatening. Therefore, lifelong anticoagulation is required, which has side effects and may not be effective. In this study, peripheral blood mononuclear cells from a patient with severe antithrombin deficiency were reprogrammed into induced pluripotent stem cells (iPSCs). The mutation was corrected using CRISPR-Cas9 and Cre/LoxP genome editing. iPSCs were differentiated into hepatocytes, which were injected into the spleen of antithrombin knockout mice to restore the activity of antithrombin and reduce the thrombophilic state. Human iPSC-differentiated hepatocytes colonized mice and secreted antithrombin stably, normalizing antithrombin in plasma (activity: from 46.8 ± 5.7% to 88.6 ± 7.6%, P < 0.0001; antigen: from 146.9 ± 19.5 nanograms per milliliter to 390.7 ± 16.1 nanograms per milliliter, P < 0.0001). In venous thrombosis model, the rate of thrombosis in mice treated with edited hepatocytes, parental hepatocytes, and wild-type mice were 60, 90, and 70%, respectively. The thrombus weight was much lighter in mice treated with edited hepatocytes compared with parental hepatocytes (7.25 ± 2.00 milligrams versus 15.32 ± 2.87 milligrams, P = 0.0025) and showed no notable difference compared with that in wild-type mice (10.41 ± 2.91 milligrams). The activity and concentration of antithrombin remained high for 3 weeks after injection. The liver and kidney function markers showed no obvious abnormality during the observation period. This study provides a proof of principle for correction of mutations in patient-derived iPSCs and potential therapeutic applications for hereditary thrombophilia.

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.

Hereditary Thrombophilia in the Era of COVID-19

Thrombophilia, also called hypercoagulability or prothrombotic condition, usually reflects a certain imbalance that occurs either in the coagulation cascade or in the anticoagulation/fibrinolytic system. A similar imbalance may be induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Thrombotic complications are associated with multiorgan failure and increased mortality. In this context, activation of coagulation and thrombocytopenia appeared as prognostic markers in COVID-19. Our work provides a structured and updated analysis of inherited thrombophilia and its involvement in COVID-19, emphasizing the importance of diagnosing and initiating thromboprophylaxis. Since the state of hypercoagulation is directly correlated with COVID-19, we consider that studies on the genetic profiles of proteins involved in thrombophilia in patients who have had COVID-19 and thrombotic events are of great importance, both in treating and in preventing deaths due to COVID-19.

Platelet-HIV: interactions and their implications

While it is clear that platelets interact with viruses, the ramifications and mechanisms of those interactions are still being defined for each type of viral infection. HIV/AIDS⁺ represents a potentially unique example of how viremia affects platelets since the increasing efficacy of antiretroviral therapeutics (ART) has made it a chronic disease that increases the risk of cardiovascular disease. In this opinion article, we discuss some of the open questions about how platelets interact with HIV. What happens to a virion once it binds a platelet? What is the nature of virus-induced platelet activation? Are platelets a normal part of the immune response to viremia that has been co-opted to increase the spread of HIV? The answers to these and similar questions will help define how platelet-directed therapeutics might be used in treating HIV/AIDS⁺ patients.

Recurrent hematuria and painful necrotic purpura induced by acquired Protein S deficiency associated with monoclonal immunoglobulin

Protein S deficiency is associated with an increased risk of thromboembolism, which may be caused by hereditary deficiency and several physiological and pathologic conditions, such as pregnancy, contraceptive use, liver diseases, inflammatory disease, and certain viruses infections. However, monoclonal immunoglobulin-mediated Protein S deficiency is rarely reported. Here we described a 49-year-old woman with a history of recurrent painful swelling in both lower extremities due to venous thrombosis for 7 years, accompanied by recurrent gross hematuria and multiple painful necrotic purpuras for 5 years, who was then diagnosed with acquired Protein S deficiency induced by the monoclonal immunoglobulin. Then she was successfully treated with rituximab combined with anticoagulation therapy. This case highlights the rare manifestations of Protein S deficiency and the influence of the monoclonal immunoglobulin produced by monoclonal B lymphocytes and monoclonal plasma cells on the activity of Protein S, which can be treated effectively with rituximab combined with anticoagulation therapy.

Clinical Impact of Heritable Thrombophilia on Neonatal-Onset Thromboembolism: A Nationwide Study in Japan

OBJECTIVE

To clarify the incidence and genetic risk of neonatal-thromboembolism, we conducted a nationwide study exploring the impact of thrombophilia on neonatal-thromboembolism in Japan.

STUDY DESIGN

A questionnaire survey was conducted for perinatal centers in Japan, focusing on the clinical expression, genotype, treatment, and outcome of patients who developed thromboembolism within 28 days of birth from 2014 to 2018.

RESULTS

The estimated incidence of neonatal-thromboembolism was 0.39 cases per 10 000 live births. Intracranial lesions and purpura fulminans occurred in 66 and 5 of 77 patients, respectively. Fifty-eight (75.3%) infants presented within 3 days after birth. Four (5.2%) died, and 14 (18.2%) survived with disability. At the diagnosis, <20% plasma activity of protein C was noted in 16 infants, protein S (in 2), and antithrombin (in 1). Thirteen genetic tests identified 4 biallelic and 5 monoallelic protein C-variants but no protein S- or antithrombin-variants. Protein C-variants had purpura fulminans (P < .01), ocular bleeding (P < .01), positive-family history (P = .01), and death or disability (P = .03) more frequently than others. Protein C-variants were independently associated with disability (OR 5.74, 95% CI 1.16-28.4, P = .03) but not death. Four biallelic variants had serious thrombotic complications of neurologic disability, blindness, and/or amputation. Three monoallelic variants survived without complications. The only protein C-variant death was an extremely preterm heterozygote infant.

CONCLUSIONS

Monoallelic protein C-variants had a higher incidence of neonatal-thromboembolism than biallelic variants. Thrombophilia genetic testing should be performed in the setting of neonatal-thromboembolism and low protein C to identify the underlying genetic defect.

A thrombophilia family with protein S deficiency due to protein translation disorders caused by a Leu607Ser heterozygous mutation in PROS1

BACKGROUND

Protein S deficiency (PSD) is an autosomal dominant hereditary disease. In 1984, familial PSD was reported to be prone to recurrent thrombosis. Follow-up studies have shown that heterozygous protein S (PROS1) mutations increase the risk of thrombosis. More than 300 PROS1 mutations have been identified; among them, only a small number of mutations have been reported its possible mechanism to reduce plasma protein S (PS) levels. However, whether PROS1 mutations affect protein structure and why it can induce PSD remains unknown.

METHODS

The clinical phenotypes of the members of a family with thrombosis were collected. Their PS activity was measured using the coagulation method, whereas their protein C and antithrombin III activities were measured using methods such as the chromogenic substrate method. The proband and her parents were screened for the responsible mutation using second-generation whole exon sequencing, and the members of the family were verified for suspected mutations using Sanger sequencing. Mutant and wild type plasmids were constructed and transfected into HEK293T cells to detect the mRNA and protein expression of PROS1.

RESULTS

In this family, the proband with venous thrombosis of both lower extremities, the proband's mother with pulmonary embolism and venous thrombosis of both lower extremities, and the proband's younger brother had significantly lower PS activity and carried a PROS1 c. 1820 T > C:p.Leu607Ser heterozygous mutation (NM_000313.3). However, no such mutations were found in family members with normal PS activity. The PS expression in the cell lysate and supernatant of the Leu607Ser mutant cells decreased, while mRNA expression increased. Immunofluorescence localization showed that there was no significant difference in protein localization before and after mutation.

CONCLUSIONS

The analysis of family phenotype, gene association, and cell function tests suggest that the PROS1 Leu607Ser heterozygous mutation may be a pathogenic mutation. Serine substitution causes structural instability of the entire protein. These data indicate that impaired PS translation and synthesis or possible secretion impairment is the main pathogenesis of this family with hereditary PSD and thrombophilia.

Pathogenic variants of PROC gene caused type II activity deficiency in a Chinese family: A case report

RATIONALE

Hereditary Protein C (PC) deficiency is a rare genetic disorder caused by PROC gene mutation. In this article, we report a case of PC deficiency in a Chinese family due to a novel PROC gene mutation.

STUDY SUBJECT

The proband presented with recurrent cerebral infarction over the course of the previous 3 years. He was admitted to the hospital due to signs of mental retardation.

DIAGNOSES

Physical examination, laboratory tests, and magnetic resonance imaging demonstrated that the proband had a manifestation of PC deficiency that included acute cerebral infarction. DNA sequencing analysis revealed a missense variant, c.1015G > A (p.V339 M from valine to methionine) in exon 9 of the PROC gene. In addition, Sanger sequencing confirmed that the proband's son was heterozygous for the same variant. Therefore, the PROC gene mutation was transmitted in an autosomal dominant inheritance manner.

INTERVENTIONS

The patient was treated with a daily dosage of Warfarin (3.5 mg) and was scheduled to undergo regular blood coagulation tests.

OUTCOMES

At the 3-month follow-up appointment, the patient showed improvements in his overall health condition.

LESSONS

We identified a novel missense mutation in the PROC gene in a Chinese family which caused a decrease in the PC antigen level and recurrent cerebral infarction.

A Rare Thrombophilic Occurrence: Dural Venous Sinus Thrombosis in a Patient with Significant Family History of Protein S Deficiency

Protein S is a potent anticoagulant that downregulates thrombin formation and is a vitamin K-dependent glycoprotein which is primarily synthesized in the liver. A deficiency in this protein or decreased activity, as seen in hereditary protein S deficiency, can lead to life-threatening thrombosis. Hereditary protein S deficiency is a rare disease as listed by the National Organization for Rare Disorders (NORD). It is known to cause venous as well as arterial thromboembolic events commonly occurring in the deep leg and pelvic veins. Dural venous sinus thrombosis is a rare consequence of protein S deficiency and is associated with a risk of increased morbidity and mortality. We report a case of dural venous sinus thrombosis in a patient with a family history of protein S deficiency in nine family members. A 53-year-old female presented to the ED with a three-day history of persistent left-sided headache, left facial numbness with tingling, and photophobia. She denied any visual disturbances, slurring of speech, and/or unilateral weakness. Some 10 years prior to this episode, she was placed on warfarin therapy for deep vein thrombosis (DVT) of lower extremity, but she discontinued it after three years of treatment without consulting her treating physician. She was taking oral contraceptive pills (OCPs) for two years and discontinued one month ago. She has nine family members with protein S deficiency, but the patient was never screened for a hypercoagulable state. On admission, her vital signs were within normal limits. Pupils were round and reactive to light, neck was supple, there was a sensory deficit for pinprick on the left V2-V3 distribution, and remainder of the cranial nerves and neurologic examination was unremarkable. CT scan of the head demonstrated a hyper-density within the left transverse and sigmoid sinus suspicious for dural venous sinus thrombosis. This was confirmed by CT angiogram showing a filling defect throughout the transverse sinus and sigmoid sinus extending below the jugular bulb into the superior aspect of the jugular vein. Intravenous heparin and warfarin were initiated. As the patient had severe trypanophobia and IV heparin required frequent activated partial thromboplastin time (APTT) monitoring, this was later changed to subcutaneous low-molecular-weight heparin and warfarin. Subsequent thrombosis panel showed a reduced protein S activity of 15% and low levels of total and free protein S antigens. She was discharged home with life-long warfarin therapy. In conclusion, cerebral dural venous sinus thrombosis is a rare and potentially life-threatening condition that can be seen in hereditary protein S deficiency. A high degree of suspicion in young females with worsening headache and neurologic signs and symptoms will help with timely diagnosis and management avoiding serious consequences. In a patient with a family history of thrombophilia, as seen in our patient, screening is important in order to confirm an underlying thrombophilic state. Such testing may have helped our patient regarding education on avoiding potential risk factors for thrombophilia and importance of treatment adherence.

Prevalence and Outcomes of Thrombophilia in Patients with Acute Pulmonary Embolism

Background

We aimed to study the prevalence and outcomes of thrombophilia in acute pulmonary embolism.

Methods

A retrospective observational study was conducted to include patients with a radiologically confirmed diagnosis of PE screened for thrombophilia from May 2011 to February 2015. Data included patients’ demographics; clinical presentation, risk factors, laboratory investigations, management, and outcome were analyzed and compared in patients with and without thrombophilia.

Results

A total of 227 cases of PE were included in the study, of which 108 (47.6%) had thrombophilia. The most frequent coagulopathic abnormality included deficiency of protein S, protein C, and antithrombin III and hyperhomocysteinemia. Only seven out of 79 patients were found to have factor V Leiden. PE patients diagnosed with thrombophilia were 10 years younger in age and peaked in the age range 30–39 years. Prior history of DVT (p=0.001) and PE (p=0.001) were the main significant risk factors in the thrombophilia group. The frequency of different risk categories of clinical probability scores did not differ significantly among those with and without thrombophilia. Pulmonary hypertension was a common complication in the thrombophilia group (P=0.009). Medications used included warfarin (74.7%), enoxaparin (73.9%), and heparin (55.4%). The overall mortality rate was 8.4%, and was non-significantly higher in the non-thrombophilia group.

Conclusion

Deficiencies of protein S, protein C, and antithrombin III are the leading causes of thrombophilic defects. Patients with hereditary thrombophilia are at increased risk of acute PE, particularly among young individuals. Therefore, early detection of thrombophilic defects together with other unprovoked risk factors could reduce the risk of recurrent VTE.

Protein C Deficiency

Protein C (PC) deficiency is a heritable or acquired risk factor for thrombophilia, with presentations varying from asymptomatic to venous thromboembolism to neonatal purpura fulminans, a life-threatening disorder. Hereditary PC deficiency is caused by mutation in the PC (PROC) gene located on chromosome 2q14.3. Heterozygous and acquired PC deficiencies are more common than homozygous deficiency. The recommended initial laboratory test measures PC activity using either clot-based or chromogenic methods. There are numerous potential interferences in PC activity testing that may result in either false-positive (falsely low activity) or false-negative (falsely normal or elevated activity) results. In the present review, we discuss common clinical presentations; laboratory testing, with a focus on potential assay interferences; treatment options; and prognosis in patients with PC deficiency.

The secondary prevention of venous thromboembolism: Towards an individual therapeutic strategy

After the anticoagulant withdrawal, a substantial proportion of patients with venous thromboembolism will develop recurrent events. Whether to consider an extended treatment depends on the risk of recurrence and bleeding risk. The assessment of the individual risk profile remains a difficult task. Several basal and post-basal factors modulate the risk of recurrence and may help clinicians to select patients who can benefit from the extended therapy. During the year 2017, new evidence regarding the post-basal factors was provided by the Morgagni and Scope studies. Another interesting novelty was the VTE-BLEED score, the first bleeding risk score that obtained the external validation in venous thromboembolism setting. In secondary prevention, the use of direct oral anticoagulants is growing instead of vitamin K antagonist. Even at lower doses, direct oral anticoagulants showed to be effective and safe, to reduce all-cause mortality and seemed to be superior to placebo for the composite outcome of fatal bleeding and fatal recurrence. After the recently published Einstein-Choice trial, the role of aspirin has become truly marginal as rivaroxaban 10 mg showed a bleeding risk similar to aspirin 100 mg but a greater effectiveness reducing the relative risk of recurrence by about 70%. Another option for secondary prevention could be sulodexide, with a lower protective effect than direct oral anticoagulants but an interesting safety profile. In conclusion, in our opinion, an individual strategy taking into account the risk of recurrence, bleeding risk, therapeutic options and patient preferences is the most appropriate approach to secondary prevention of venous thromboembolism.

Detection of high-risk thrombophilia with an automated, global test: the Coagulation Inhibitor Potential assay

: The diagnosis of thrombophilia is a cost-consuming and time-consuming process, as each defect should be separately investigated. The Coagulation Inhibitor Potential (CIP) assay is a promising new global test, sensitive for most of the hereditary thrombophilias, developed for manual methodology. We adapt the original method to an optical coagulation analyser. By this automation, the test will be easier, faster and more precise, and it also allows carrying out 18 measurements simultaneously. The CIP assay was performed in 126 healthy subjects and 193 patients with different types of hereditary thrombophilia conditions. Detected with conventional laboratory tests high-risk thrombophilia was present in 70 patients: deficiencies of antithrombin (AT) (n = 12), protein C (PC) (n = 14), protein S (PS) (n = 6), homozygous factor V Leiden (FVL) mutation (n = 9) and combined types (n = 29). Low-risk thrombophilia was present in 123 patients: heterozygous FVL (n = 115) and FII G2010A mutation (n = 8). Significantly lower median CIP values were found for AT-,PC-, PS deficiencies, homozygous and heterozygous FVL mutations and combined thrombophilias (P < 0.01) as compared with healthy controls. There was no significant difference between the heterozygous FIIG20210A (P = 0.669) thrombophilia group and the healthy controls. The best performance of the test was achieved at the cut-off value of 90.0 U (area: 0.981) with 96% sensitivity and 92% specificity in the high-risk thrombophilia group estimated by receiver operating characteristic analysis. The new method seems to be appropriate and reliable for the detection of AT-, PC- and PS deficiencies, homozygous FVL mutation and also for combined deficiencies. The automated CIP test is insensitive to FII G2010A mutation.

Optimal utilization of thrombophilia testing

The global incidence of venous thromboembolism is high so laboratory testing for hereditary thrombophilia and selected acquired thrombophilia is common. Given the costs associated with testing and multiple pre-analytic and analytic variables affecting the assays, careful patient selection and timing of testing and diligent application to patient management are critical to providing high-value clinical care. Collaboration between the ordering providers and performing laboratories has the potential to achieve these goals. Herein, utility of thrombophilia testing, variables that affect the assays, and impact on patient management are reviewed. Where available, information on cost-effectiveness is discussed.

Recurrent Deep Vein Thrombosis After the First Venous Thromboembolism Event: A Single-Institution Experience

BACKGROUND We investigated the frequency, clinical presentation, risk factors, and outcome after the first deep vein thrombosis (DVT) event. MATERIAL AND METHODS A retrospective study was conducted for patients with DVT between 2008 and 2012 with a 1-year follow-up. Patients were divided into 2 groups: single vs. recurrent DVT (RDVT). RESULTS Of the 6420 patients screened for DVT, 662 (10.3%) had DVT. RDVT constituted 22% of cases. A single event was more frequent in left lower limb DVT (p=0.01), while RDVT cases had more bilateral DVT (p=0.01). Recurrent pulmonary embolism (PE) and comorbidities were significantly higher in the RDVT group (P<0.05). Protein C, protein S, and anti-thrombin III deficiency were higher in patients with RDVT (P<0.05). Post-thrombotic syndrome was significantly higher among RDVT cases (p=0.01). In addition, obesity, abnormal coagulation, and prior history of PE and bilateral DVT were found to be independent predictors of RDVT. The PE rate was greater with RDVT than those with single events (22% vs. 9%, p=0.001); however, during follow-up and after adjustment for age and sex, this effect was statistically insignificant (adjusted HR 1.23, 95% CI 0.43-3.57, p=0.68). The age- and sex-adjusted mortality rate was higher in patients with single events with a HR 2.3; 95%CI 1.18-4.54 (p=0.01); however, this effect disappeared after adjusting for the duration of warfarin therapy (p=0.22). CONCLUSIONS Patients with RDVT are common and have characteristic features that required more attention and further evaluation. These findings should help identifying high-risk patients and set effective preventive measures for RDVT that may revise the duration of warfarin therapy.

ANMCO Position Paper: long-term follow-up of patients with pulmonary thromboembolism

Venous thromboembolism (VTE), including pulmonary embolism and deep venous thrombosis, is the third most common cause of cardiovascular death. The management of the acute phase of VTE has already been described in several guidelines. However, the management of the follow-up (FU) of these patients has been poorly defined. This consensus document, created by the Italian cardiologists, wants to clarify this issue using the currently available evidence in VTE. Clinical and instrumental data acquired during the acute phase of the disease are the cornerstone for planning the FU. Acquired or congenital thrombophilic disorders could be identified in apparently unprovoked VTE during the FU. In other cases, an occult cancer could be discovered after a VTE. The main targets of the post-acute management are to prevent recurrence of VTE and to identify the patients who can develop a chronic thromboembolic pulmonary hypertension. Knowledge of pathophysiology and therapeutic approaches is fundamental to decide the most appropriate long-term treatment. Moreover, prognostic stratification during the FU should be constantly updated on the basis of the new evidence acquired. Currently, the cornerstone of VTE treatment is represented by both the oral and the parenteral anticoagulation. Novel oral anticoagulants should be an interesting alternative in the long-term treatment.

Heparan sulfate/heparin glycosaminoglycan binding alters inhibitory profile and enhances anticoagulant function of conserved Amblyomma americanum tick saliva serpin 19

Some serine protease inhibitor (serpin) regulators of essential life pathways bind glycosaminoglycans (GAGs) to enhance inhibitory functions and achieve physiologically relevant rates. This study demonstrates that highly conserved Amblyomma americanum tick saliva serpin 19 (AAS19), a broad-spectrum inhibitor of hemostasis and inflammation system proteases and anticoagulant, can bind heparan sulfate/heparin (HS)GAGs and that this interaction alters its function. Substrate hydrolysis and unpaired t-test analyses revealed that HSGAG binding caused rAAS19 inhibitory activity to: (i) significantly increase against blood clotting factors (f) IIa (thrombin) and fIXa, (ii) significantly reduce against fXa and fXIIa and (iii) moderate to no effect against trypsin, kallikrein, papain, and plasmin. Stoichiometry of inhibition (SI) analyses show that HSGAG binding improved the rAAS19 inhibitory efficiency against thrombin 2.7-4.3 fold as revealed by SI change from 13.19 in absence of HSGAGs to 4.83-3.04 in their presence. Our data show that HSGAG binding dramatically enhanced rAAS19 anticoagulant function. In the recalcification time assay, rAAS19 pre-incubated with HSGAGs prior to the assay, delayed plasma clotting by an additional 176-457 s above HSGAGs or rAAS19 alone. Our data suggest that formation of the HSGAGs and rAAS19 complex is important for the observed enhanced anticoagulant effect. Delay of plasma clotting was higher when HSGAGs and rAAS19 were co-incubated to allow complex formation prior to blood clotting assay as opposed to no co-incubation. We have discussed our finding with reference to tick feeding physiology and utility of the rAAS19 in blood clotting disorder therapy.

Impact of high risk thrombophilia status on recurrence among children and adults with VTE: An observational multicenter cohort study

BACKGROUND

Antithrombin [AT]-, protein C [PC]- or protein S [PS]-deficiency [D] constitutes a major risk factor for venous thromboembolism [VTE]. Primary study objective was to evaluate if the clinical presentation at first VTE onset differs between children and adults and to compare the individual recurrence risk among patients with respect to age at onset and their thrombophilia status ATD, PCD or PSD.

METHODS/PATIENTS/RESULTS

In 137 of 688 consecutively enrolled pediatric and adult VTE patients we calculated the absolute risk of VTE recurrence and event-free-survival adjusted for thrombophilia and positive family VTE history. At first VTE children manifested i) with a lower rate of pulmonary embolism, ii) a higher rate of cerebral vascular events or multiple VTEs, and iii) showed a higher proportion of unprovoked VTE compared to adolescents and adults. Adult patients reported more often a positive VTE history compared to younger study participants. The adjusted odds of recurrence in adults was 2.05 compared to children.

CONCLUSION

At disease manifestation children and adults differ with respect to i) thrombotic locations, ii) percentage of unprovoked versus provoked VTE, and iii) different rates of positive VTE family histories. Furthermore, adults showed a two-fold increase risk of VTE recurrence compared to children.

Impact of high-risk thrombophilia status on recurrence among children with a first non-central-venous-catheter-associated VTE: an observational multicentre cohort study

Deficiency of antithrombin (AT), protein C (PC) or protein S (PS) constitutes a major risk factor for venous thromboembolism (VTE). Individuals at high risk for recurrence who benefit from screening need to be identified. The primary study objective was to determine the individual recurrence risk among children with a first non-central-venous-catheter-associated VTE with respect to their thrombophilia status and to evaluate if the clinical presentation at first VTE onset differs between children with AT, PC or PS deficiency versus no thrombophilia. We calculated the absolute risk of VTE recurrence and event-free-survival adjusted for thrombophilia, age, sex and positive family VTE history in 161 consecutively enrolled paediatric VTE patients. The presence of a deficiency relative to no thrombophilia was evaluated as a potential predictor of recurrence. Predictors for recurrence were AT deficiency (hazard ratio/95% CI: 6·5/2·46-17·2) and female gender (2·6/1·1-6·35). The annual recurrence rates (95% CIs) were 5·4% (2·6-10) in AT-deficient children, 1·3% (0·3-3·8) in patients with PC deficiency, 0·7% (0·08-2·4) in the PS-deficient cohort and 0·9% (0·4-1·8) in patients with no thrombophilia. Positive family VTE history or combined thrombophilias did not predict recurrence. Given the overall annual incidence rate of recurrence of 1·5% we suggest screening for AT deficiency in children with VTE.

Venous thromboembolism: Predicting recurrence and the need for extended anticoagulation

Initial treatment for venous thromboembolism (VTE) includes the acute and intermediate phases, usually lasting for 3 months. The choice to extend therapy beyond the initial 3-month window involves assessing a combination of risk factors for VTE recurrence and bleeding, along with weighing patient preferences. In some cases, such as VTE provoked by a reversible surgical risk factor, the recurrence risk is sufficiently low that most patients should not receive extended therapy. In other cases, such as VTE associated with malignancy, the recurrence risk is sufficiently high that treatment should be extended beyond the initial 3 months. However, a large number of patients fall into a grey zone where the decision on extended therapy is less clear-cut. In this review, we summarize the evidence for VTE recurrence risk and the role for extended anticoagulation given a variety of patient-specific factors and laboratory results. We also review the role of VTE risk prediction tools and provide a recommended algorithm for approaching the decision of extended anticoagulation therapy. Various agents available for extended VTE therapy, including warfarin, aspirin and the direct oral anticoagulant agents, are discussed.

The epidemiology of venous thromboembolism

Venous thromboembolism (VTE) is categorized by the U.S. Surgeon General as a major public health problem. VTE is relatively common and associated with reduced survival and substantial health-care costs, and recurs frequently. VTE is a complex (multifactorial) disease, involving interactions between acquired or inherited predispositions to thrombosis and VTE risk factors, including increasing patient age and obesity, hospitalization for surgery or acute illness, nursing-home confinement, active cancer, trauma or fracture, immobility or leg paresis, superficial vein thrombosis, and, in women, pregnancy and puerperium, oral contraception, and hormone therapy. Although independent VTE risk factors and predictors of VTE recurrence have been identified, and effective primary and secondary prophylaxis is available, the occurrence of VTE seems to be relatively constant, or even increasing.

Investigation into the effects of antioxidant-rich extract of Tamarindus indica leaf on antioxidant enzyme activities, oxidative stress and gene expression profiles in HepG2 cells

The leaf extract of Tamarindus indica L. (T. indica) had been reported to possess high phenolic content and showed high antioxidant activities. In this study, the effects of the antioxidant-rich leaf extract of the T. indica on lipid peroxidation, antioxidant enzyme activities, H₂O₂-induced ROS production and gene expression patterns were investigated in liver HepG2 cells. Lipid peroxidation and ROS production were inhibited and the activity of antioxidant enzymes superoxide dismutase, catalase and glutathione peroxidase was enhanced when the cells were treated with the antioxidant-rich leaf extract. cDNA microarray analysis revealed that 207 genes were significantly regulated by at least 1.5-fold (p < 0.05) in cells treated with the antioxidant-rich leaf extract. The expression of KNG1, SERPINC1, SERPIND1, SERPINE1, FGG, FGA, MVK, DHCR24, CYP24A1, ALDH6A1, EPHX1 and LEAP2 were amongst the highly regulated. When the significantly regulated genes were analyzed using Ingenuity Pathway Analysis software, “Lipid Metabolism, Small Molecule Biochemistry, Hematological Disease” was the top biological network affected by the leaf extract, with a score of 36. The top predicted canonical pathway affected by the leaf extract was the coagulation system (P < 2.80 × 10⁻⁶) followed by the superpathway of cholesterol biosynthesis (P < 2.17 × 10⁻⁴), intrinsic prothrombin pathway (P < 2.92 × 10⁻⁴), Immune Protection/Antimicrobial Response (P < 2.28 × 10⁻³) and xenobiotic metabolism signaling (P < 2.41 × 10⁻³). The antioxidant-rich leaf extract of T. indica also altered the expression of proteins that are involved in the Coagulation System and the Intrinsic Prothrombin Activation Pathway (KNG1, SERPINE1, FGG), Superpathway of Cholesterol Biosynthesis (MVK), Immune protection/antimicrobial response (IFNGR1, LEAP2, ANXA3 and MX1) and Xenobiotic Metabolism Signaling (ALDH6A1, ADH6). In conclusion, the antioxidant-rich leaf extract of T. indica inhibited lipid peroxidation and ROS production, enhanced antioxidant enzyme activities and significantly regulated the expression of genes and proteins involved with consequential impact on the coagulation system, cholesterol biosynthesis, xenobiotic metabolism signaling and antimicrobial response.

Epidemiology of venous thromboembolism

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

Natural anticoagulants deficiency and the risk of venous thromboembolism: a meta-analysis of observational studies

INTRODUCTION

Natural anticoagulants deficiency (antithrombin [AT], protein C [PC], protein S [PS]) is a rare, but potent risk factor for venous thromboembolism (VTE). We performed a meta-analysis of observational studies evaluating the impact of inherited natural anticoagulants deficiency on VTE risk.

MATERIALS AND METHODS

Case-control and cohort studies evaluating the association of these abnormalities with VTE were systematically searched in the PubMed, Web of Science, Scopus and EMBASE databases.

RESULTS

Twenty-one studies were included in the analysis. Thirteen studies (3,452 cases and 11,562 controls) showed an increased risk of first VTE in AT deficient subjects compared to controls (OR: 16.26, 95%CI:9.90-26.70; P<0.00001). An increased risk of first VTE was also found in PC (11 studies, 2,554 cases and 9,355 controls; OR: 7.51, 95%CI:3.21-17.52; P<0.00001) and PS deficient patients (14 studies, 4,955 cases and 9,267 controls; OR: 5.37; 95%CI:2.70-10.67; P<0.00001) compared to controls. Evaluating the risk of VTE recurrence, we found a significant association with AT (4 studies, 142 cases and 1,927 controls; OR: 3.61; 95%CI:1.46-8.95; P=0.006) and with PC (2 studies, 80 cases and 546 controls; OR: 2.94; 95%CI:1.43-6.04; P=0.03), but not with PS deficiency (2 studies, 57 cases and 589 controls; OR: 2.52; 95%CI:0.89-7.16; P=0.08). Sensitivity and subgroup analyses confirmed these results. The association among natural anticoagulants deficiency and VTE was maximal for patients with unprovoked events.

CONCLUSION

The VTE risk is increased in patients with natural anticoagulants deficiency, but additional studies are warranted to better assess the risk of VTE recurrence.

Compound heterozygous protein C deficiency in a family with venous thrombosis: Identification and in vitro study of p.Asp297His and p.Val420Leu mutations

Hereditary protein C deficiency (PCD) is an autosomal inherited disorder associated with high risk for venous thromboembolism (VTE). This study aimed to explore the functional consequences of two missense mutations, p.Asp297His and p.Val420Ile, responsible for type I/II PCD and recurrent deep vein thrombosis (DVT) in a Chinese family. The plasma protein C activities (PC:A) of the proband and his sister were reduced to 4% and 5% of normal activity. However, protein C antigen (PC:Ag) concentrations were not equally decreased, with levels of 90.5% and 88.7%, respectively. Two missense mutations p.Asp297His and p.Val420Leu were identified in the protein C gene (PROC). The PC:A and PC:Ag levels in heterozygous state for p.Asp297His were 66% and 64.8%, whereas in heterozygous state for p.Val420Leu, these levels were 67% and 145%, respectively. Wild type (WT) and two mutant PROC cDNA expression plasmids were constructed and transfected into HEK 293T cells. Western blot analysis revealed that both p.Asp297His and p.Val420Leu showed a normal intracellular protein level. The extracellular protein level and specific activity of p.Asp297His were equally reduced to 37.7 ± 4.3% and 22.1 ± 2.5%, respectively. Mutant p.Val420Leu showed a relatively higher PC:Ag level and undetectable PC:A. Immunofluorescence staining revealed that WT and p.Val420Leu proteins were largely co-localized with both the protein disulfide isomerase (PDI) and cis-Golgi Marker (GM130), while the PC p.Asp297His mutant protein was mainly co-localized with PDI and much less co-localized with GM130. The thrombosis symptom in this family was associated with the two missense mutations in the PROC gene.

Thrombophilia Screening

Although controversial, screening for thrombophilia has become common. Testing for antiphospholipid antibodies is indicated in order to guide treatment decisions if there is clinical suspicion for antiphospholipid syndrome. The utility of identifying other thrombophilias in symptomatic venous thromboembolism (VTE) is questionable, as the risk of recurrence does not appear to be increased by an appreciable degree with the most common disorders (heterozygosity for factor V Leiden or prothrombin mutation). Although recurrence appears to be increased in those with homozygous or multiple abnormalities and potentially deficiencies in natural anticoagulants, screening to detect these conditions is difficult to justify based on their rarity. The American College of Chest Physicians' current guidelines note the increased risk of recurrence with idiopathic, proximal events regardless of thrombophilia status. They suggest duration of anticoagulation therapy be based on location and provoking factors rather than whether or not the individual has a thrombophilia. Because routine prophylaxis in asymptomatic individuals with thrombophilia is not recommended, screening of asymptomatic family members is difficult to justify. Screening prior to prescribing combination oral contraceptives is not cost effective, may result in unwanted pregnancies, and may have little effect on the overall rate of VTE.

A systematic review of the utility of residual vein obstruction studies in primary and secondary venous thrombosis

Background. Residual vein obstruction (RVO), the persistence of venous thrombosis with time and often after anticoagulation, may indicate a systemic prothrombotic condition. Prior studies have shown varying efficacy in using RVO as a risk factor for future venous thromboembolic (VTE) recurrence. Methods. To assess whether positive RVO imaging predicts recurrent VTE events, we performed a meta-analysis on studies in which patients with documented VTEs, anticoagulated for a minimum of 4 weeks, had repeat sonography to assess RVO and were subsequently followed for recurrent events. Results. Thirteen studies met inclusion criteria: 3531 patient VTE events with 3474 evaluable results were analyzed. The presence of RVO was associated with recurrence in all VTE (OR 1.93; 95% CI: 1.29, 2.89) and secondary VTE (OR 2.78; 95% CI: 1.41, 5.5) but not for primary VTE (OR 1.35; 95% CI: 0.87, 2.08). When cancer patients were eliminated from the secondary VTE group, there was no longer a significant association of RVO with VTE recurrence (OR 1.73; 95% CI: 0.81, 3.67) while in the subset of cancer patients, presence of RVO was associated with an increase in VTE recurrence risk (OR 5.14; 95% CI: 1.59, 16.65, P < 0.006). Conclusions. We conclude that the presence of RVO is associated with recurrence in secondary VTE but not in primary VTE and that association may be driven by the subset with cancer.

The superiority of anti-FXa assay over anti-FIIa assay in detecting heparin-binding site antithrombin deficiency

OBJECTIVES

Antithrombin is a progressive inhibitor of active factor X (FXa) and thrombin (FIIa). Its effect is 500- to 1,000-fold accelerated by heparin or heparan sulfate. Heterozygous type I (quantitative) and most type II (qualitative) antithrombin deficiencies highly increase the risk of venous thromboembolism (VTE), while homozygous mutations are lethal. The functional defect affecting the heparin-binding site confers moderate risk of VTE to heterozygous and high risk of VTE to homozygous individuals.

METHODS

Antithrombin activity assays based on the inhibition of FIIa and FXa were compared for their efficiency in detecting heparin-binding site defects.

RESULTS

With a single exception, in heterozygotes for heparin-binding site defects (n = 20), anti-FIIa activities remained in the reference interval, while anti-FXa activities were uniformly decreased. In individuals who were homozygous for heparin-binding site mutations (n = 9), anti-FIIa activities were in the range of 48% to 80%; the range of anti-FXa activities was 9% to 25%. Anti-FIIa and anti-FXa activities in type I deficiencies and type II pleiotropic deficiency did not differ significantly.

CONCLUSIONS

Anti-FXa antithrombin assay is recommended as a first-line test to detect type II heparin-binding site antithrombin deficiency.

Protein S levels and the risk of venous thrombosis: results from the MEGA case-control study

Low free protein S and low total protein S levels could not identify subjects at risk for venous thrombosis in a population-based study. Protein S testing and subsequent testing on PROS1 mutations should not be considered in unselected patients with venous thrombosis.

Prevalence of thrombophilia according to age at the first manifestation of venous thromboembolism: results from the MAISTHRO registry

Thrombophilia is a well-established risk factor for a venous thromboembolic event (VTE), and it has been proposed that hereditary thrombophilia may substantially contribute to the development of VTE in young patients. We aimed to analyse the prevalence of thrombophilia with special regard to the age of VTE manifestation. The study cohort consisted of 1490 patients (58% females) with a median age 43 years at the time of their first VTE. At least one thrombophilic disorder was identified in 50·1% of patients. The probability of detecting a hereditary thrombophilia declined significantly with advancing age (from 49·3% in patients aged 20 years and younger to 21·9% in patients over the age of 70 years; P < 0·001). This may be primarily attributed to the decreasing frequencies of the F5 R506Q (factor V Leiden) mutation and deficiencies of protein C or protein S with older age at the time of the initial VTE event. Moreover, thrombophilia was more prevalent in unprovoked compared with risk-associated VTE (57·7% vs. 47·7%; P = 0·001). The decline in the prevalence of hereditary thrombophilia with older ages supports the use of a selected thrombophilia screening strategy dependent on age and the presence or absence of additional VTE risk factors.

Overview and assessment of risk factors for pulmonary embolism

Pulmonary embolism is one of the most common undiagnosed conditions affecting hospitalized patients. There are a plethora of risk factors for venous thromboembolism and pulmonary emboli. These factors are grouped under the broad triad of hypercoagulability, stasis and injury to provide a framework for understanding. Important risk factors include inherited thrombophilia, age, malignancy and estrogens. These risk factors are reviewed in detail and several risk assessment models are reviewed. These risk assessment models help identify those at risk for disease and therefore candidates for thromboprophylaxis. Diagnosis can be difficult and is aided by clinical decision rules that incorporate clinical scores that define the likelihood of pulmonary embolism. These are important considerations, not only for diagnostic purposes, but also to minimize excessive use of imaging, which increases exposure to and risks associated with radiation. A healthy index of suspicion is often the key to diagnosis.

Deficiency of antithrombin and protein C gene in 202 Chinese venous thromboembolism patients

INTRODUCTION

Antithrombin and protein C gene deficiencies are commonly inherited risk factors for VTE patients. We aim to investigate the deficiency of these two gene in 202 Chinese patients with venous thromboembolism (VTE).

METHODS

Antithrombin activity (AT: A) and protein C activity (PC: A) were measured in 202 VTE patients, and for those with unexplainable low results, PCR and direct sequencing of the related genes were carried out.

RESULTS

Deficiency levels of antithrombin and protein C gene were found to be 2% and 8%, respectively. AT or PC hereditary deficiency can be found in 10% patients with VTE.

CONCLUSION

Protein C gene deficiency might be more prevalent than AT gene deficiency in Chinese VTE patients. Functional assay combined with genetic analysis is useful in the diagnosis of inherited defects in VTE patients.

Testing for inherited thrombophilia and consequences for antithrombotic prophylaxis in patients with venous thromboembolism and their relatives. A review of the Guidelines from Scientific Societies and Working Groups

The clinical penetrance of venous thromboembolism (VTE) susceptibility genes is variable, being lower in heterozygous carriers of factor V Leiden and prothrombin 20210A (mild thrombophilia), and higher in the rare carriers of deficiencies of antithrombin, protein C or S, and those with multiple or homozygous abnormalities (high-risk thrombophilia). The absolute risk of VTE is low, and the utility of laboratory investigation for inherited thrombophilia in patients with VTE and their asymptomatic relatives has been largely debated, leading to the production of several Guidelines from Scientific Societies and Working Groups. The risk for VTE largely depends on the family history of VTE. Therefore, indiscriminate search for carriers is of no utility, and targeted screening is potentially more fruitful. In patients with VTE inherited thrombophilia is not scored as a determinant of recurrence, playing a minor role in the decision of prolonging anticoagulation; indeed, a few guidelines consider testing worthwhile to identify carriers of high-risk thrombophilia, particularly those with a family history of VTE. The identification of the asymptomatic carrier relatives of the probands with VTE and thrombophilia could reduce cases of provoked VTE, offering them primary antithrombotic prophylaxis during risk situations. In most guidelines, this is considered justified only for relatives of probands with a deficiency of natural anticoagulants or multiple abnormalities. Counselling the asymptomatic female relatives of individuals with VTE and/or thrombophilia before pregnancy or the prescription of hormonal treatments should be administered with consideration of the risk driven by the type of thrombophilia and the family history of VTE.

Venous thrombosis: understanding the paradoxes of recurrence

The decision to continue anticoagulant treatment in patients with a first venous thrombosis after the initial treatment period has strong, life-long implications. Both the risk of recurrence when treatment is stopped and the risk of bleeding when it is continued are high and will persist over a patient's lifetime. For clinicians, rational strategies to stratify their patients into levels of risk of recurrence are limited. To support in the decision to continue or not, it is of the utmost importance to understand why some people develop a second event and others do not and how these people can be identified. This is not easy as, contrary to intuition, the risk profile of a recurrent event is entirely different from that of a first: Some genetic factors that have a major effect on first thrombosis only marginally predict recurrence, while, for instance, the opposite is true for male sex. These paradoxes can be explained when we understand etiology of a first event, how rates for first and second event cannot be directly compared, and how fixed risk factors cannot be predictors, while factors that are not causes can yet be predictors. Integrating all knowledge and combining the best predicting variables will ultimately lead to ways to estimate an individual's recurrence risk and hence to decide on optimal further treatment.

Management of patients with unprovoked venous thromboembolism: an evidence-based and practical approach

OPINION STATEMENT

The management of patients with unprovoked venous thromboembolism is a common and challenging clinical problem. Although the initial antithrombotic management is well-established, there is uncertainty about the optimal long-term anticoagulant management, specifically whether patients should receive a short (i.e., 3- to 6-month) duration of anticoagulant therapy or indefinite anticoagulation. Factors that may be considered to estimate patients' risk for recurrent thromboembolism include the mode of initial clinical presentation, as deep vein thrombosis or pulmonary embolism, patient sex, antecedent hormonal therapy use, thrombophilia, D-dimer levels, and residual vein occlusion in patients with deep vein thrombosis. Many of these factors have been integrated into clinical prediction guides which stratify patients with unprovoked venous thromboembolism according to their risk for disease recurrence and, thereby, can assist clinicians in decisions about the duration of anticoagulation. The objective of this review is to consider the evidence relating to the clinical significance of purported risk factors and provide a practical case-based approach to guide decisions on duration of anticoagulation for patients with unprovoked venous thromboembolism.

Hereditary thrombophilia in Korean patients with idiopathic pulmonary embolism

PURPOSE

Hereditary thrombophilia (HT) is a major risk factor for idiopathic pulmonary embolism (iPE) and shows different prevalence among ethnic groups. The prevalence and clinical characteristics of HT in Korean patients with iPE were investigated.

MATERIALS AND METHODS

Patients with PE on computed tomography (CT) scan were recruited, and those with malignancy were excluded. Patients were divided into iPE and provoked PE (pPE) groups. The presence of HT in the iPE group was assessed by DNA sequencing of the corresponding gene in patients who had low levels of natural anticoagulants. The clinical characteristics of iPE with HT (iPE/HT+) were compared with those of iPE without HT (iPE/HT-) and pPE.

RESULTS

Out of 161 patients, 84 patients had iPE and 77 patients had pPE. Among 54 patients in the iPE group whose coagulation profiles were tested, 28 patients were diagnosed with HT (51.9%; 28/54). Compared with the iPE/HT- and pPE groups, the iPE/HT+ group showed the highest proportion of male patients (71.4%; p<0.001); the youngest mean age (44±14 years; p<0.001); and the highest frequencies for history of venous thromboembolism (64.3%; p<0.001), concurrent deep vein thrombosis (75.0%; p=0.021), and adverse clinical outcomes (42.9%, p<0.001). Protein C deficiency was the most common HT. On molecular genetic tests, causative mutation was identified in 13 patients.

CONCLUSION

In this study of Korean patients, about half of the patients with iPE had HT. Patients with iPE and HT were mostly young males with deep venous thrombosis (DVT), previous venous thromboembolism (VTE), and frequent adverse clinical outcomes. Therefore, Korean patients with iPE should be tested for HT.