A series of 10 Polish patients with thromboembolic events and antithrombin deficiency: two new c.1154-1 G>C and c.1219-534 A>G SERPINC1 gene splicing mutations.

: Inherited antithrombin (AT) deficiency, with prevalence in the general population ranging 0.02-0.17%, is an autosomal dominant disorder associated with a high risk of venous thromboembolism. In most cases, deficiency is caused by mutations in the AT-coding gene (SERPINC1). Only 24 splicing defects have been described causing AT deficiency, all affecting exon flanking regions. The aim of the current study was to characterize the mutations underlying AT deficiency in 10 venous thromboembolism Polish patients aged 42.9 (14-63) years. Whole SERPINC1 gene sequencing was done by next generation sequencing methods. Eight cases had mutations previously described. However, we identified two new intronic mutations that might affect the correct splicing of exon 6 according to in-silico predictions: c.1154-1 G>C, which strongly disturbs the acceptor sequence and c.1219-534 A>G, a deep intronic mutation that might generate a cryptic donor sequence; both might compete with the wild-type donor sequence and explain the associated moderate AT deficiency of carriers. In conclusion, we show the molecular base of AT deficiency in 10 new Polish patients, including two novel SERPINC1 gene mutations potentially affecting splicing.

High detection rates of antithrombin deficiency and antiphospholipid syndrome in outpatients aged over 50 years using the standardized protocol for thrombophilia screening.

INTRODUCTION: Thrombophilia screening has limited detection efficiency. We assessed the detection rate when a standardized approach to thrombophilia-screened outpatients was used. METHODS: We analyzed 1185 patients (36.5% males, median age: 43 years [IQR 33-54]) referred to a single center from January 2014 to October 2017 with 11 different clinical indications for thrombophilia screening, which was performed in the adherence to published guidelines. Factor V Leiden, prothrombin G20210A mutation, antithrombin (AT), protein C, protein S deficiencies and antiphospholipid syndrome (APS) were determined. RESULTS: The overall positivity rate was 37.1% (95% CI 34.3%-39.7%). The highest positivity rate was found in women following VTE during pregnancy/childbirth (64.1%) and provoked VTE patients with positive family history (52.9%). In patients aged >50 years (32.5%), APS was found at a similar rate as in younger subjects (11.4% vs 10.1%), while AT deficiency was detected more frequently in the older group (5.7% vs 2.4%, p = 0.003). CONCLUSIONS: Standard indications for thrombophilia screening lead to detection rates of 37% or more. Frequent detection of APS and AT deficiency among older patients, which often implies a need for long-term anticoagulation and could impact clinical practice patterns, suggests a benefit of thrombophilia screening in this population in selected clinical circumstances.

Mild antithrombin deficiency and risk of recurrent venous thromboembolism: results from the MEGA follow-up study.

Essentials Mild antithrombin deficiency may increase the risk of recurrent venous thromboembolism (VTE). In a cohort study, we stratified patients with VTE to various cut-off antithrombin levels. A 1.6-3.7-fold increased risk of recurrent VTE was observed in the lowest antithrombin categories. Mild antithrombin deficiency (activity < 5th percentile of normal) increases recurrent VTE risk. SUMMARY: Background Mild antithrombin deficiency (previously defined as antithrombin activity below 70% or 80%) has been associated with a 2.4-3.5-fold increased risk of recurrent venous thromboembolism (VTE). This finding may have implications for duration of antithrombotic therapy in VTE patients with mild antithrombin deficiency. Objectives To externally validate whether mild antithrombin deficiency is a risk factor for recurrent VTE. Methods In a population-based cohort study, patients with a first VTE (n = 2357) were stratified according to percentile cut-off antithrombin levels (< 5th [< 87%], 5-10th [87-92%], > 10th percentile [> 92%]) and functional antithrombin levels (< 70%, 70-80%, > 80%). Results During a median follow-up of 7.4 years, 361 recurrent events occurred (incidence rate, 2.5/100 patient-years). We observed an increased risk of recurrent VTE in the lowest antithrombin activity category (< 5th percentile; < 87%) as compared with antithrombin activity that was > 10th percentile (> 92%), with an adjusted hazard ratio (HR) of 1.5 (95%CI, 1.0-2.3). When analyses were stratified to antithrombin cut-off criteria of< 70% vs. patients with antithrombin activity > 80%, the adjusted HR for venous recurrence was 3.7 (95% CI, 1.4-9.9). Mild antithrombin deficiency was able to predict recurrent VTE over at least 8 years of follow-up and the association remained present when the population was stratified to the presence or absence of thrombosis risk factors. Restriction analyses, where patients who used anticoagulation at time of blood draw and those who reported drinking ≥ 5 glasses alcohol daily were excluded, did not materially affect these outcomes. Conclusion This study confirms that mild antithrombin deficiency is a risk factor for recurrent VTE.

Liver dysfunction in women with pregnancy-induced antithrombin deficiency.

AIM: The aim of this study was to determine whether women with pregnancy-induced antithrombin deficiency (PIATD) had higher risk of liver dysfunction in the absence of thrombocytopenia. METHODS: We carried out a retrospective observational study at five centers in all 129 women with incidentally found PIATD among 5249 maternities and 129 control women without PIATD matched for number of fetuses and gestational week at delivery. PIATD was diagnosed in women with antenatal antithrombin (AT) activities of ≤75% followed by a further decrease to ≤65% peripartum. Liver dysfunction was defined as serum aspartate aminotransferase >  45 IU/L concomitant with lactate dehydrogenase >  400 IU/L. Thrombocytopenia was defined as platelet count < 120 × 109 /L. RESULTS: Thrombocytopenia (22% [28/129] vs 5.4% [7/129], P =  0.0001) and liver dysfunction (16% [20/129] vs 0.0% [0/129], P =  0.0000) occurred significantly more often in PIATD than in control women. Of the 20 women with liver dysfunction, 15 (75%) had PIATD, but not thrombocytopenia. Thus, even in the absence of thrombocytopenia, liver dysfunction occurred significantly more often in PIATD than in control women (15% [15/101] vs 0.0% [0/122], respectively, P =  0.0000). The relative risk (95% confidence interval) of liver dysfunction was 28.6 (1.64-500) for women with AT activity of 60-65% and 52.4 (3.17-865) for women with AT activity of <60%, compared to women with AT activity ≥66%. CONCLUSION: PIATD can occur in the absence of thrombocytopenia and PIATD women had higher risk of liver dysfunction even in the absence of thrombocytopenia.

Genetic Risk Factors in Venous Thromboembolism.

Genetic risk factors predispose to thrombophilia and play the most important etiopathogenic role in venous thromboembolism (VTE) in people younger than 50 years old. At least one inherited risk factor could be found in about half of the cases with a first episode of idiopathic VTE.Roughly, genetic risk factors are classified into two main categories: loss of function mutations (such as deficiencies of antithrombin, protein C, protein S) and gain of function mutations, (such as prothrombin mutation G20210A, factor V Leiden). A revolutionary contribution to the genetic background of VTE was brought by the achievements of the genome-wide association studies which analyze the association of a huge number of polymorphisms in large sample size.Hereditary thrombophilia testing should be done only in selected cases. The detection of hereditary thrombophilia has impact on the management of the anticoagulation in children with purpura fulminans, pregnant women at risk of VTE and may be useful in the assessment of the risk for recurrent thrombosis in patients presenting an episode of VTE at a young age (<40 years) and in cases with positive family history regarding thrombosis.

Age-specific onset and distribution of the natural anticoagulant deficiency in pediatric thromboembolism.

BACKGROUND: The early diagnosis of inherited thrombophilia in children is challenging because of the rarity and hemostatic maturation. METHODS: We explored protein C (PC), protein S (PS), and antithrombin (AT) deficiencies in 306 thromboembolic patients aged ≤20 y using the screening of plasma activity and genetic analysis. RESULTS: Reduced activities were determined in 122 patients (40%). Low PC patients were most frequently found in the lowest age group (0-2 y, 45%), while low PS or low AT patients were found in the highest age group (16-20 y; PS: 30% and AT: 20%). Genetic study was completed in 62 patients having no other causes of thromboembolism. Mutations were determined in 18 patients (8 PC, 8 PS, and 2 AT genes). Six of eight patients with PC gene mutation were found in age 0-2 y (75%), while six of eight patients with PS gene mutation were in 7-20 y. Two AT gene-mutated patients were older than 4 y. Four PC-deficient and two PS-deficient patients carried compound heterozygous mutations. All but one PC gene-mutated patient suffered from intracranial thromboembolism, while PS/AT gene-mutated patients mostly developed extracranial venous thromboembolism. CONCLUSION: Stroke in low PC infants and deep vein thrombosis in low PS/AT school age children could be targeted for genetic screening of pediatric thrombophilias.

Risk factors and recurrent thrombotic episodes in patients with cerebral venous thrombosis.

BACKGROUND: The prevalence of thrombophilic abnormalities in patients with cerebral vein thrombosis has been reported to be similar to that in patients with deep vein thrombosis of the lower limb. The role of gender-specific risk factors (pregnancy, oral contraceptives) is well established, whereas that of other acquired risk conditions is debated. MATERIALS AND METHODS: We screened 56 patients with cerebral vein thrombosis and 184 age- and sex-matched apparently healthy controls for prothrombin (factor II, FII) G20210A and factor V Leiden polymorphisms; protein S, protein C, and antithrombin deficiency; anticardiolipin antibodies; hyperhomocysteinaemia and other putative risk factors. RESULTS: The G20210A polymorphism was found in 29.1% of patients and in 5.7% of controls (odds ratio [OR] 7.1; P<0.0001; adjusted OR 12.67, P<0.0001). Frequencies of factor V Leiden and hyperhomocysteinaemia were not significantly different in patients and controls, nor were the other thrombophilic tests and some established cardiovascular risk factors, such as smoking, obesity or overweight and arterial hypertension. Conversely, 53.7% of the women who developed cerebral vein thrombosis did so while assuming oral contraceptives (OR 6.12; P<0.0001), with a further increase of risk in FII G20210A carriers (OR 48.533). Some associated diseases (onco-haematological disorders and infections) also had a significant role. Over a median 7-year follow-up, irrespective of the duration of antithrombotic treatment, 9/56 (16%) patients had further episodes of venous/arterial thrombosis. No significant risk factor for recurrent thrombosis was identified. DISCUSSION: In spite of the limitations of the sample size, our data confirm the role of FII G20210A mutation in this setting and its interactions with acquired risk factors such as oral contraceptives, also highlighting the risk of recurrent thrombosis in cerebral vein thrombosis patients.

[The activity levels and prevalence of deficiency of protein C, protein S and antithrombin in Chinese Han population].

OBJECTIVE: To explore the distribution and influence factors of protein C (PC), protein S (PS) and antithrombin (AT) activities and to determine the prevalence of their deficiencies in the Chinese Han healthy population. METHODS: Healthy volunteers including blood donors and individuals for routine check-up were recruited from 4 Chinese medical centers. The plasma levels of PC, PS and AT activities were measured. The plasma levels of activities were measured by chromogenic substrate assay (AT and PC) and clotting assay (PS). RESULTS: A total of 3493 healthy Chinese adults had been recruited in this study. Males had higher PS and PC activities than females, especially for PS (P < 0.01). PC activities increased with age in both sexes but decreased in men after 50 years old. There was no significant change with age were of PS in 50 years old, while there was a decline in males and a rise in females above 50 years old. AT tended to increase with age in women but decreased with age in men after 50 years old. Based on the age and gender, the general prevalence of PC, PS and AT deficiencies in the general Chinese Han population were 1.15%, 1.49% and 2.29%, respectively. CONCLUSION: PC, PS and AT activities have correlation with age and gender in Chinese Han population. Reference range should be laid down and deficiencies should be identified

Thrombophilia among Chinese women with venous thromboembolism during pregnancy.

AIMS: To assess the prevalence of thrombophilia among Chinese women with venous thromboembolism (VTE) developed during pregnancy. METHODS: Based on information from a tertiary teaching unit, all recorded cases of deep vein thrombosis (DVT) and pulmonary embolism (PE) during pregnancy diagnosed between 1997 and 2005, were assessed for prevalence of thrombophilia. Fifty-five healthy women, who had at least one normal pregnancy but without any previous history of VTE, were recruited as controls. RESULTS: A total of 44 subjects completed thrombophilia screening, of whom 5 (11%) were confirmed to have thrombophilia [protein C (PC) deficiency (2), protein S (PS) deficiency (1), combined PC & PS deficiency (1) and antithrombin III deficiency (1)]. Homozygous 5,10-methylenetetrahydrofolate reductase (C677T) gene mutation was found in 6 (14%) subjects but not in the controls. There was no antiphospholipid syndrome, activated PC resistance, factor V Leiden or prothrombin gene mutations. CONCLUSION: In the Chinese population, PS and PC deficiencies are common thrombophilia for VTE during pregnancy and thrombophilia screening should be recommended in all pregnant women who suffer from VTE.

Thrombophilia in childhood: to test or not to test.

Inherited thrombophilia is defined as a genetically determined tendency to develop venous thromboembolism. In children, inherited thrombophilia contributes to the development of pediatric thromboembolic disease. As a consequence, pediatric hematologists are increasingly requested to test thrombophilia in pediatric patients with thrombosis or asymptomatic children from thrombophilic families. This article reviews the benefits and limitations of testing for thrombophilic disorders, for example, factor V Leiden, prothrombin mutation, and deficiencies of antithrombin, protein C, or protein S in childhood.

Molecular basis of antithrombin deficiency.

Antithrombin (AT) is the most important physiological inhibitor of coagulation proteases. It is activated by glycosaminoglycans such as heparin. Hereditary antithrombin deficiency is a rare disease that is mainly associated with venous thromboembolism. So far, more than 200 different mutations in the antithrombin gene (SERPINC1) have been described. The aim of our study was to characterise the molecular background in a large cohort of patients with AT deficiency. Mutation analysis was performed by direct sequencing of SERPINC1 in 272 AT-deficient patients. Large deletions were identified by multiplex PCR coupled with liquid chromatography or multiplex ligation-dependent probe amplification (MLPA) analysis. To predict the effect of SERPINC1 sequence variations on the pathogenesis of AT deficiency, in silico assessments, multiple sequence alignment, and molecular graphic imaging were performed. The mutation profile consisted of 59% missense, 10% nonsense, 8% splice site mutations, 15% small deletions/insertions/duplications, and 8% large deletions. Altogether 87 different mutations, including 42 novel mutations (22 missense and 20 null mutations), were identified. Of the novel missense mutations, nine are suspected to impair the conformational changes that are needed for AT activation, two to affect the central reactive loop or the heparin binding site, and six to impair the structural integrity of the molecule. Despite the heterogeneous background of AT deficiency, 10 AT variants occurred in multiple index patients. Characterisation of the SERPINC1 mutation profile in large cohorts of patients may help to further elucidate the pathogenesis of AT deficiency and to establish genotype-phenotype associations.

Usefulness of antithrombin deficiency phenotypes for risk assessment of venous thromboembolism: type I deficiency as a strong risk factor for venous thromboembolism.

Inherited antithrombin deficiency, an established risk factor for venous thromboembolism (VTE), can be classified into type I (quantitative deficiency) or type II (qualitative deficiency). In the present study, we assessed the VTE risk associated with the phenotypes of antithrombin deficiency in patients admitted to our hospital. We found that patients with type I deficiency (n = 21) had more VTE events and earlier onset of VTE than those with type II deficiency (n = 10). The VTE-free survival analysis showed that the risk for VTE in patients with type I deficiency was sevenfold greater than that in patients with type II deficiency (hazard ratio: 7.3; 95% confidence interval: 1.9-12.2; P = 0.0009). The prevalence of type I deficiency in the VTE group (5.6%, 6/108) was higher than that in the general population (0.04%, 2/4,517) (odds ratio: 132.8; 95% confidence interval: 26.5-666.1; P < 0.0001). However, the prevalence of type II deficiency was not different between the VTE group and the general population. Our study indicated that the risk for VTE in patients with type I deficiency was much higher than that in patients with type II deficiency. Thus, simple phenotypic classification of antithrombin deficiency is useful for assessment of VTE risk in Japanese.

Increased thrombophilic tendency in pediatric cystic fibrosis patients.

Thrombophilia has recently been reported to be increased in patients with cystic fibrosis (CF). We wanted to determine whether this was applicable to our population with CF and how our patients compared to the previously reported groups. Seventy one pediatric CF patients were assessed for a thrombophilic tendency, using a lupus anticoagulant screen, protein C, protein S, antithrombin assay, and activated protein C resistance (APCR) screen. The incidence of activate protein C resistance (4.2%) was within expected limits for the general population as was the incidence of antithrombin deficiency. However there was a marked increase in the incidence of lupus anticoagulants (18%) and 14% and 19.7% of the patients showed a reduced protein C and protein S, respectively, far in excess of the general population. This increased incidence of thrombophilia was not related to any specific CF phenotype and while perturbed liver function cannot be entirely ruled out, it appeared unlikely to be responsible for all the abnormal coagulation findings. Despite the apparent thrombophilic tendency, no clinically evident thrombotic episodes were noted during the study period. Thrombophilia is of concern because of the increasingly frequent placement of indwelling catheters in CF patients. The precise cause for the thrombophilic tendency in CF patients is unknown at this stage.

Superficial venous thrombosis: role of inherited deficiency of natural anticoagulants in extension to deep veins.

AIM: Superficial venous thrombosis (SVT) has been considered for a long time a limited clinical condition of low importance, but this approach has changed in recent years, when several studies demonstrated that extension to deep veins occurs in 7.3 to 44% of patients, with high prevalence of pulmonary embolism. The aim of this study was to evaluate the prevalence of inherited deficiency of natural coagulation inhibitors in patients suffering from SVT in both normal and varicose veins, and to understand their role in extension to deep veins. METHODS: The study included 83 patients with SVT, without clinically obvious risk factors. Ultrasound examination was performed, and deficiencies of Protein C, Protein S and Antithrombin (AT) were investigated. RESULTS: In the patients where SVT occurred in normal veins, coagulation inhibitor deficiencies were 6.45% in the absence of extension and 62.5% in patients with extension to deep veins. In the patients with varicose vein SVT, the presence of these factors was less evident, but their prevalence was considerably higher in those with extension to deep veins (36.3%) than in non-extension (6.06%). CONCLUSIONS: Present data confirm the role of inherited thrombophilic states related to inhibitor deficiency, considering them as risk factors for SVT in normal veins. Furthermore, an association has been found between their presence and the progression of SVT to deep veins.

Antithrombin after cardiac surgery: implications on short and mid-term outcome.

BACKGROUND: Antithrombin (AT) drop during cardiac surgery has been described. The causes and the effects of this phenomenon are not clear. The objective of the study is to evaluate the relationship of AT postoperative values on short and mid-term outcome after cardiac surgery. METHODS: Between January and June 2005, 405 patients, who underwent cardiac operations at our Institution had AT values available preoperatively and postoperatively. Using Receiver Operating Characteristic curves, a cut-off equal to 63.7% for ICU-arrival AT was chosen in order to divide the entire population in two groups (117 patients with ICU-arrival AT < 63.7%, Low AT group, and 288 patients with ICU-arrival AT > or = 63.7%, High AT group). Objective of the study was to evaluate the predictive role of ICU-arrival AT < 63.7% on in-hospital mortality and morbidity and on 18 months follow-up after cardiac surgery. RESULTS: ICU-arrival AT was significantly lower than preoperative AT (90.7 +/- 16.3% vs. 71.2 +/- 15.1%, P < 0.0001). Patients in the Low AT group were older, more often female, had a worse Euroscore and required longer CPB duration and cross clamp time. They had significantly higher preoperative and postoperative D-dimer levels. ICU arrival AT < 63.7% was not associated with increased in-hospital mortality but it was an independent risk factor for longer mechanical ventilation, need of inotropic support, excessive bleeding and blood products transfusion. ICU arrival-AT < 63.7% was associated with worse survival during 18 months follow up (92.3% vs. 85.4% in the High AT and Low AT group, respectively, P = 0.05). CONCLUSIONS: Low AT after cardiac surgery is associated with higher incidences of peri-operative complications and worse survival in the mid-term. Future studies should clarify the pathophysiologic mechanism of this findings and possible therapeutic directions.

[Progression from a routine examination to a study. Having come this far, what should be done from now? A thrombosis risk factor study].

We were able to carry out a study of deep venous thrombosis (DVT) with the cooperation of clinicians. I herein describe a part of the study that I have conducted. Japanese patients with DVT were investigated regarding their incidences of antithrombin III (AT-III), protein C (PC), and protein S (PS) deficiencies, and the results were compared with those of normal subjects. We confirmed that the Japanese population has a high frequency of PC and PS deficiencies. Furthermore, we recommend that PS activity should be measured for the screening of thrombosis since type II deficiency accounted for approximately 50% of PS deficiency cases in both patients and the normal group in Japanese. We evaluated the reactivity of thrombin to TM by determining the TM-bound thrombin (TMBTh) to total thrombin generation (t-Th) ratio (TMBT ratio). We also examined whether a decreased TMBT ratio is associated with an increased risk of thrombosis. The TMBT ratio (TMBTh/t-Th) was significantly lower in patients with DVT than in control subjects. These results suggest that it is possible to evaluate the reactivity of thrombin to TM by determining the TMBT ratio, and this ratio may be a predictor of deep vein thrombosis. However, we have yet to investigate the causal mechanism.