Hereditary Antithrombin Research Articles

Association of hereditary antithrombin deficiency with intrauterine growth restriction

: Antithrombin is a major suppressor of thrombin, factor Xa and blood coagulation. Inherited antithrombin deficiency is rare and is considered among the common causes of inherited thrombophilia. The relationship between antithrombin and IUGR, is questionable. The aim of this study was to trace the relationship between antithrombin deficiency and the intrauterine weight reduction and neonatal morbidity. The study was conducted on 55 full-term neonates (including 25 baby boys and 30 baby girls), all were admitted to Neonatal Intensive Care Unit in Cairo University Hospitals with IUGR; and another 110 healthy full-term neonates as control group. ATIII activities were assessed in citrated of patient and control samples automatically on coagulometer (Stago, France). There was a highly significant relationship regarding ATIII deficiency in IUGR group in relation to control group (P value <0.001). In conclusion, we have identified antithrombin deficiency in Egyptian infants as an additional cause for low-birth weight and intrauterine growth retardation.

β-Antithrombin, subtype of antithrombin deficiency and the risk of venous thromboembolism in hereditary antithrombin deficiency: A family cohort study

Hereditary antithrombin deficiency is associated with a high incidence of venous thromboembolism (VTE), but VTE risk differs between families. Beta-antithrombin is reported to be the most active isoform of antithrombin in vivo. Whether β-antithrombin activity and subtypes in antithrombin deficiency have impact on VTE risk has not been investigated outside the proband setting.We performed a retrospective family cohort study to investigate whether subtypes of antithrombin deficiency or β-antithrombin levels are associated with the risk of first or recurrent VTE.Eighty-one subjects from 21 families were included, of which 52 were antithrombin deficient. Βeta-antithrombin levels were decreased in most type I and type IIPE subjects, but normal levels were found in all subtypes of antithrombin deficiency.The annual incidence of VTE in antithrombin-deficient family members was 1.24%, 95%CI: 0.72–1.99%, in low β-antithrombin 1.36% (95%CI: 0.76–2.25%) and in normal β-antithrombin 0.79% (95%CI: 0.10–2.77). The annual incidence of recurrence in family members was 3.1% (95%CI: 0.9–7.1%). Duration of anticoagulation had an impact on recurrence risk: In family members annual recurrence with fixed duration was 10% (95%CI: 2.1–29.2%), with indefinite duration 1.5% (95%CI: 0.2–5.4%), p < 0.05. Beta-antithrombin levels were not associated with the risk for first or recurrent VTE in antithrombin deficient subjects. ConclusionsIn this high-risk antithrombin-deficient population, both subjects with low and normal plasma β-antithrombin activity had high risks of first and recurrent VTE. This puts the importance of β-antithrombin into question. Long-term anticoagulation is warranted in antithrombin-deficient VTE patients.

Management of hereditary antithrombin deficiency in pregnancy

Antithrombin (AT) deficiency is a high-risk thrombophilia and a rare condition. Despite full anticoagulation during pregnancy and the postpartum period, women with AT deficiency may still be vulnerable to developing venous thromboembolism (VTE), including fatal events. There is limited guidance on the management of AT deficiency in pregnancy, including the role of AT concentrates. Following a comprehensive review of the state of the art with respect to recommendations and guidelines, our expert panel in maternal-fetal medicine, hematology and basic science reached consensus on key issues in the recognition and management of AT deficiency in pregnancy. This paper summarizes the state of the art and summarizes what we believe are best practices with special emphasis on a multidisciplinary approach involving obstetrics and hematology in the care of women with AT deficiency.

P-093: Three cases of heparin-resistant deep vein thrombosis (DVT) during pregnancy due to hereditary antithrombin (AT) deficiency

P-093: Three cases of heparin-resistant deep vein thrombosis (DVT) during pregnancy due to hereditary antithrombin (AT) deficiency

Management of Venous Thromboembolism in Patients with Hereditary Antithrombin Deficiency and Pregnancy: Case Report and Review of the Literature

Background. Hereditary antithrombin deficiency is a thrombogenic disorder associated with a 50–90% lifetime risk of venous thromboembolism (VTE), which is increased during pregnancy and the puerperium in these patients. We present a case of a woman with antithrombin (AT) deficiency who presented with a VTE despite therapeutic low molecular weight heparin (LMWH). Though the pregnancy was deemed unviable, further maternal complications were mitigated through the combined use of therapeutic anticoagulation and plasma-derived antithrombin concentrate infusions to normalize her functional antithrombin levels. Methods. A review of the literature was conducted for studies on prophylaxis and management of VTE in pregnant patients with hereditary AT deficiency. The search involved a number of electronic databases, using combinations of keywords as described in the text. Only English language studies between 1946 and 2015 were included. Conclusion. Antithrombin concentrate is indicated in pregnant women with hereditary AT deficiency who develop VTE despite being on therapeutic dose anticoagulation. Expert opinion suggests AT concentrate should be used concomitantly with therapeutic dose anticoagulation. However, further high-quality studies on the dose and duration of treatment in the postpartum period are required. Use of AT concentrate for prophylaxis is controversial and should be based on individual VTE risk stratification.

Issues in the Diagnosis and Management of Hereditary Antithrombin Deficiency.

To review insights gained in the past several years about hereditary antithrombin (AT) deficiency and to outline approaches to the management of patients with AT deficiency in the acute and chronic settings. An extensive literature search of Scopus (January 2008-April 2016) was performed for the terms congenital antithrombin deficiency, inherited antithrombin deficiency, or hereditary antithrombin deficiency Additional references were identified by reviewing literature citations. All relevant English-language case reports, reviews, clinical studies, meeting abstracts, and book chapters assessing hereditary AT deficiency were included. AT deficiency significantly increases the risk of venous thromboembolism (VTE). The risk of VTE is particularly high during pregnancy, the postpartum period, and following major surgery. Effective clinical management includes determination of the appropriate type and duration of antithrombotic therapy (ie, AT replacement for acute situations) while minimizing the risk of bleeding. For persons newly diagnosed with AT deficiency, age, lifestyle, concurrent medical conditions, family history, and personal treatment preferences can be used to individualize patient management. Patients should be informed of the risks associated with hormonal therapy, pregnancy, surgical procedures, and immobility, which further increase the risk of VTE in patients with AT deficiency. AT deficiency poses the highest risk for VTE among the hereditary thrombophilias, often requiring long-term anticoagulation. Undertaking an evaluation for hereditary thrombophilia is controversial; however, a diagnosis of VTE in association with AT deficiency can have management implications. An important treatment option for patients with this disorder in high-risk situations is AT concentrate.

Phenotypic and genetic analysis of two pedigrees affected with hereditary antithrombin deficiency

To explore the phenotype, genotype and molecular mechanism for two pedigrees affected with hereditary antithrombin (AT) deficiency. Clinical diagnosis was validated by assaying of coagulation parameters including prothrombin time, activated partial thromboplastin time, thrombin time, fibrinogen, antithrombin activity (AT:A) and specific antigen (AT:Ag), protein C activity, as well as protein S activity. To detect potential mutations in the probands, all exons, exon-intron boundaries and the 3', 5' untranslated regions were amplified by PCR and subjected to direct sequencing. Suspected mutation was confirmed by reverse sequencing and silver staining. The effect of mutations on the AT protein was analyzed with bioinformatics software. The AT:Ag of pedigree 1 was normal, but its AT:A has reduced to 30%. A heterozygous c.235C>T mutation in exon 2 causing p.Arg47Cys, in addition with two single nucleotide polymorphisms (c.981G>A, c.1011G>A) in exon 5 were identified in the patient. His four children, except for the elder daughter, were heterozygous for the mutations. The plasma levels of AT:A and AT:Ag in proband 2 have decreased to 39% and 103 mg/L, respectively. A heterozygous deletion (g.5890-5892delCTT) leading to loss of p.Phe121 was also detected in his father. Bioinformatic analysis suggested that the missense mutation Arg47Cys can affect the functions of AT protein. Meanwhile, lacking of Phe121 will result in loss of hydrogen bonds with Ala124, Lys125 and the cation π interactions with Lys125, Arg47, which may jepordize the stability of the protein. The proband 1 had type II AT deficiency, while proband 2 had type I AT deficiency. The p.Arg47Cys and g.5890-5892delCTT mutations of the AT gene are significantly correlated with the levels of AT in the two probands, respectively.

Hereditary Antithrombin Deficiency with Hemorrhagic Cerebral Infarction and Cardiac Thrombosis Occurred in Neonatal Period: A Case Report

Antithrombin (AT) is the main inhibitor of blood coagulation proteases. Hereditary AT deficiency is an autosomal-dominant thrombophilic disorder caused by a SERPINC1 abnormality, it represents a risk factor for thromboembolic disease. A 25-day-old male infant was referred to Severance Children's Hospital for hemorrhagic cerebral infarction with hydrocephalus. The initial laboratory study showed 11% AT activity. An approximate 4 mm-×-3 mm-size thrombosis was also found in the right ventricle by echocardiography. We found two deletion in the coding and flanking sequences of SERPINC1 c.235C>T (p.Arg79Cys) and c.442T>C (p.Ser148Pro) at 10 months of age. The p.Ser148Pro mutation was found in his mother but the other was not. This case is a rare thrombotic event that occured early year in due to AT deficiency. Our patient had side effects after heparin treatment, so aspirin therapy was employed. No thrombotic events occurred until 1 year of age. pISSN 2233-5250 / eISSN 2233-4580 http://dx.doi.org/10.15264/cpho.2015.22.2.151 Clin Pediatr Hematol Oncol 2015;22:151∼154

Development of a novel, rapid assay for detection of heparin-binding defect antithrombin deficiencies: the heparin-antithrombin binding (HAB) ratio

IntroductionQualitative and quantitative antithrombin deficiency predisposes to thrombosis, although patients with heparin-binding dysfunction have a lower incidence than other sub-types. Assays discriminating between qualitative sub-types are not widely available. Patients/MethodsExtended heparin incubation in antithrombin activity assays can overestimate levels in patients with HBDs. Plasmas from genetically proven HBD patients were assayed for antithrombin activity by factor Xa-inhibition and thrombin-inhibition at varying incubation times. Optimal pairings were assessed for generating a quantifiable discrepancy in HBDs by deriving a ratio between results from short and prolonged heparin-incubation assays respectively, the Heparin-antithrombin binding (HAB) ratio. Fourteen patients with hereditary antithrombin deficiency, including five with HBDs, were analysed. ResultsThe FXa-inhibition assay with 30s and 300s incubations clearly identified a heterozygous p.Pro73Leu and homozygous p.Leu131Phe, giving HAB ratios of 0.24 and 0.67 respectively (reference range 0.90 – 1.01). However, three plasmas containing mutations with markedly reduced or absent heparin affinity (p.Lys146Glu, p.Gln150Pro, p.Arg79Cys) gave normal results. Nine antithrombin deficient plasmas were tested with the thrombin-inhibition assay and all generated reduced HAB ratios whilst two normal donors did not. The three available HBD plasmas generated lower values than non-HBD plasmas. The mildly reduced HAB ratios in non-HBD deficiencies may have been due to heparin cofactor II reacting with bovine thrombin during extended incubation. ConclusionsHAB ratio from FXa-inhibition assays distinguishes some but not all HBD from non-HBD antithrombins, and thrombin-inhibition assays may be diagnostically applicable with sub-type specific cut-offs.

Perioperative and peripartum prevention of venous thromboembolism in patients with hereditary antithrombin deficiency using recombinant antithrombin therapy

Recombinant human antithrombin (rhAT; ATryn), isolated from the milk of transgenic goats, provides an alternative to human plasma-derived antithrombin (AT) concentrate for perioperative and peripartum prophylaxis of venous thromboembolism (VTE) in patients with hereditary AT deficiency. Optimized rhAT dosing algorithms and improved plasma AT monitoring protocol were used in an open-label, single-arm, multinational, pivotal safety and efficacy study that was conducted in patients with hereditary AT deficiency in perioperative and peripartum settings. Loading and maintenance doses were calculated on the basis of pretreatment AT activity levels. Specific dosing regimens were used for pregnant and surgical patients; rhAT was to be given for at least 3 days and for 14 days or less. The primary efficacy end point was the incidence of any thromboembolic event during rhAT therapy or within 7 days of rhAT discontinuation. Safety and AT activity levels were secondary end points. Six surgical and 12 pregnant patients were treated for a median of 3.2 days (range 0.9-14 days). With the optimized dosing regimens, a median of 1 dose adjustment (range 0-6 dose adjustments) was needed to maintain AT activity levels within 80-120% of normal. No confirmed VTEs occurred during treatment or in the subsequent 7 days. Overall, rhAT was well tolerated, but some bleeding complications occurred after rhAT discontinuation and anticoagulation reinstitution. No antibodies to rhAT or goat milk proteins were detected. Perioperative and peripartum prophylactic rhAT therapy in patients with hereditary AT deficiency is well tolerated and effective in preventing VTE.

Discordant diagnoses obtained by different approaches in antithrombin mutation analysis

ObjectivesIn hereditary antithrombin (AT) deficiency it is important to determine the underlying mutation since the future risk of thromboembolism varies considerably between mutations. DNA investigations are in general thought of as flawless and irrevocable, but the diagnostic approach can be critical. We therefore investigated mutation results in the AT gene, SERPINC1, with two different approaches. Design and methodsSixteen patients referred to the Centre for Thrombosis and Haemostasis, Odense University Hospital, with biochemical indications of AT deficiency, but with a negative denaturing high-performance liquid chromatography (DHPLC) mutation screening (routine approach until recently) were included. As an alternative mutation analysis, direct sequencing of all exons and exon–intron boundaries without pre-selection by DHPLC was performed. ResultsOut of sixteen patients with a negative DHPLC mutation screening, discordant results were found in ten patients (62.5%) when using direct sequencing: Eight had the Basel mutation (c.218C>T), while two had the Cambridge II mutation (c.1246G>T). For seven of the ten patients this meant an altered clinical risk-assessment for future thromboses. ConclusionsAwareness must be drawn to the possibility of differences in DNA diagnostics in general and advances when using newer techniques in particular. One should consider re-analysis of results obtained by earlier sequencing strategies, as clinically important information can be overlooked.

Characterization of Thrombate III®, a pasteurized and nanofiltered therapeutic human antithrombin concentrate

Thrombate III® is a highly purified antithrombin concentrate that has been used by clinicians worldwide for more than two decades for the treatment of hereditary antithrombin deficiency. The manufacturing process is based on heparin-affinity chromatography and pasteurization. To modernize the process and to further enhance the pathogen safety profile of the final product, despite the absence of infectious disease transmission, a nanofiltration step was added. The biochemical characterization and pathogen safety evaluation of Thrombate III® manufactured using the modernized process are presented. Bioanalytical data demonstrate that the incorporation of nanofiltration has no impact on the antithrombin content, potency, and purity of the product.Scaledown models of the manufacturing process were used to assess virus and prion clearance under manufacturing setpoint conditions. Additionally, robustness of virus clearance was evaluated at or slightly outside the manufacturing operating limits. The results demonstrate that pasteurization inactivated both enveloped and non-enveloped viruses. The addition of nanofiltration substantially increased clearance capacities for both enveloped and non-enveloped viruses by approximately 4–6 log10. In addition, the process achieves 6.0 log10 ID50 prion infectivity clearance. Thus, the introduction of nanofiltration increased the pathogen safety margin of the manufacturing process without impacting the key biochemical characteristics of the product.

Impact of the type of SERPINC1 mutation and subtype of antithrombin deficiency on the thrombotic phenotype in hereditary antithrombin deficiency

Mutations in the antithrombin (AT) gene can impair the capacity of AT to bind heparin (AT deficiency type IIHBS), its target proteases such as thrombin (type IIRS), or both (type IIPE). Type II AT deficiencies are almost exclusively caused by missense mutations, whereas type I AT deficiency can originate from missense or null mutations. In a retrospective cohort study, we investigated the impact of the type of mutation and type of AT deficiency on the manifestation of thromboembolic events in 377 patients with hereditary AT deficiencies (133 from our own cohort, 244 reported in the literature). Carriers of missense mutations showed a lower risk of venous thromboembolism (VTE) than those of null mutations (adjusted hazard ratio [HR] 0.39, 95% confidence interval [CI] 0.27-0.58, p<0.001), and the risk of VTE was significantly decreased among patients with type IIHBS AT deficiency compared to patients with other types of AT deficiency (HR 0.23, 95%CI 0.13-0.41, p<0.001). The risk of pulmonary embolism complicating deep-vein thrombosis was lower in all type II AT deficiencies compared to type I AT deficiency (relative risk 0.69, 95%CI 0.56-0.84). By contrast, the risk of arterial thromboembolism tended to be higher in carriers of missense mutations than in those with null mutations (HR 6.08-fold, 95%CI 0.74-49.81, p=0.093) and was 5.9-fold increased (95%CI 1.22-28.62, p=0.028) in type IIHBS versus other types of AT deficiency. Our data indicate that the type of inherited AT defect modulates not only the risk of thromboembolism but also the localisation and encourage further studies to unravel this phenomenon.

Pharmacokinetics of Recombinant Human Antithrombin in Delivery and Surgery Patients With Hereditary Antithrombin Deficiency

Population pharmacokinetic (PK) analyses were conducted to refine dosing recommendations for recombinant human anti-thrombin therapy in surgery and delivery patients with hereditary antithrombin deficiency (HD). Single-dose PK data from patients with HD and nonlinear mixed-effects modeling were used to devise a dosing regimen to target antithrombin (AT) activity levels between 80% and 120% of normal. External validation with data from a phase 3 trial confirmed the correctness of a covariate-free model for surgery patients, but dosing adjustment was necessary for delivery patients. After different covariates were tested, the model was updated to incorporate the influential covariate, delivery. Simulations were used to develop a therapeutic drug-monitoring scenario that results in steady state AT activity levels within the target range as quickly as practically feasible. Data from a second clinical trial provided additional external validation and confirmed the accuracy of the dosing model for both groups of patients.

Prevention, management and extent of adverse pregnancy outcomes in women with hereditary antithrombin deficiency

Antithrombin (AT) deficiency is a rare hereditary thrombophilia with a mean prevalence of 0.02 % in the general population, associated with a more than ten-fold increased risk of venous thromboembolism (VTE). Within this multicenter retrospective clinical analysis, female patients with inherited AT deficiency were evaluated concerning the type of inheritance and extent of AT deficiency, medical treatment during pregnancy and postpartally, VTE risk as well as maternal and neonatal outcome. Statistical analysis was performed with SPPS for Windows (19.0). A total of 18 pregnancies in 7 patients were evaluated, including 11 healthy newborns ≥37th gestational weeks (gw), one small for gestational age premature infant (25th gw), two late-pregnancy losses (21st and 28th gw) and four early miscarriages. Despite low molecular weight heparin (LMWH) administration, three VTE occurred during pregnancy and one postpartally. Several adverse pregnancy outcomes occurred including fetal and neonatal death, as well as severe maternal neurologic disorders occurred. Patients with substitution of AT during pregnancy in addition to LMWH showed the best maternal and neonatal outcome. Close monitoring with appropriate anticoagulant treatment including surveillance of AT levels might help to optimize maternal and fetal outcome in patients with hereditary AT deficiency.

Use of recombinant human antithrombin concentrate in pregnancy

Dear editor We read with great interest James et al’s article “Prevention and treatment of venous thromboembolism in pregnancy in patients with hereditary antithrombin deficiency.” The authors reported a case series of six women with antithrombin (AT) deficiency treated with plasma derived antithrombin concentrate (pdAT; Thrombate III®, Grifols Therapeutics, Clayton, NC, USA).1 In contrast to these cases, we have managed three AT-deficient women over the past two years with low-molecular-weight-heparin during pregnancy and recombinant human antithrombin concentrate (rhAT; ATryn®, GTC Biotherapeutics, Framingham, MA, USA) at delivery. In the Phase III trial leading to approval of rhAT, pregnant women required frequent dose modifications, and an alternate dosing regimen is currently recommended by the manufacturer.2,3 The detailed information provided in these cases may assist future providers in managing pregnant patients with AT deficiency.

Prevalence of hereditary antithrombin mutations is higher than estimated in patients with thrombotic events

Antithrombin is the major inhibitor of blood coagulation, primarily inactivating thrombin and factor Xa. Inherited antithrombin deficiency is associated with an increased risk of thromboembolism. Its prevalence is estimated to be about 0.2% in the general healthy population, whereas it is 2% in patients with a history of thrombosis. We previously demonstrated thrombosis patients receiving therapeutic dosage of low-molecular-weight heparin having a lower antifactor Xa activity than originally estimated. In those patients, mutations in the AT gene (SERPINC1) were detected despite normal antithrombin activity. Thus we concluded that prevalence of antithrombin mutations might be higher than previously calculated. The aim of the present study was to investigate the prevalence of hereditary antithrombin mutations by analyzing the antithrombin gene in patients with a history of thromboembolism. Mutation analyses were performed by direct sequencing of SERPINC1 in 150 patients (aged <40 years) with thromboembolism and normal antithrombin levels. Patients with thrombophilic defects [factor V Leiden (G1691A), prothrombin (G20210T) mutation, protein C deficiency, protein S deficiency, and antiphospholipid antibodies] were excluded. The results were compared with those of 150 healthy controls without any personal history of thrombosis. Mutation analyses of all seven antithrombin exons revealed five (3.5%) patients with antithrombin mutations: three different heterozygous missense mutations were found in exon 2 and one (in two patients) in exon 7. Prevalence of inherited antithrombin mutations in thrombosis patients is higher than previously estimated. Functional antithrombin tests are unable to detect all clinically relevant antithrombin defects.

Prevention and treatment of venous thromboembolism in pregnancy in patients with hereditary antithrombin deficiency

ObjectiveThe aims of the study reported here were to provide data from six pregnant subjects who were enrolled in a clinical trial of antithrombin (AT) concentrate, discuss other published case series and case reports, and provide general guidance for the use of AT concentrate for inherited AT deficiency in pregnancy.MethodsIn the late 1980s, 31 AT-deficient subjects were enrolled in a prospective treatment trial of the plasma-derived AT concentrate Thrombate III®. Herein, newly available treatment data about the six pregnant subjects in the trial is tabulated and summarized.ResultsAll six experienced venous thromboembolism (VTE) during pregnancy, were dosed according to a weight-based protocol, and were treated concomitantly with anticoagulation. Loading doses of AT concentrate of 54–62 units/kg were followed by maintenance doses of 50%–100% of the loading dose for 3–10 days. At the time of labor, loading doses of 46–50 units/kg were followed by maintenance doses of 50%–75% of the loading dose for 5–7 days. None of the six experienced recurrent thrombosis while receiving treatment with AT concentrate.ConclusionCurrently we suggest that women with AT deficiency who are pregnant or postpartum and have a personal history of VTE or current VTE receive AT concentrates.

Molecular mechanisms of antithrombin gene mutations in 3 pedigrees with hereditary antithrombin deficiency

Molecular mechanisms of antithrombin gene mutations in 3 pedigrees with hereditary antithrombin deficiency

How I treat heterozygous hereditary antithrombin deficiency in pregnancy

Untreated hereditary antithrombin deficiency in pregnancy is associated with maternal venous thromboembolism (VTE) and possibly with fetal loss. Thromboprophylaxis during pregnancy is recommended, but dosages remain controversial.Our objective was to perform a retrospective assessment of thrombotic events and pregnancy outcomes in women with hereditary antithrombin deficiency managed according to a standard protocol. Pregnancies in individuals with hereditary antithrombin deficiency were identified from a hospital database. Women with no prior VTE received enoxaparin 40 mg daily until 16 weeks gestation and thereafter 40 mg twice daily. Women with prior VTE received intermediate dose enoxaparin (1 mg/kg) once daily, increased to twice daily at 16 weeks and anti-Xa monitored dosing. Thromboprophylaxis was stopped at initiation of labour or 12 hours prior to caesarean and 50 IU/kg antithrombin concentrate given. Thromboprophylaxis was restarted after delivery. Eighteen pregnancies in 11 women with antithrombin deficiency were identified. Seventeen pregnancies (94%) were successful. Median gestation was 39 weeks (range 30-41) and median birth-weight was 2,995 g (910-4,120 g), but 6/17 infants (35%) were small for gestational age (p=0.01). Estimated blood loss at delivery was median 375 ml (200-600 ml). Four pregnancies were complicated by VTE; one newly presented with a thrombotic event, two patients were not taking thromboprophylaxis and one occurred despite thromboprophylaxis. Two novel mutations (p.Leu317Ser and p.His33GInfsX32) are described. In conclusion, in antithrombin deficiency the use of low-molecular-weight heparin in pregnancy and puerperium with antithrombin concentrate pre-delivery was associated with successful pregnancy outcome; rates of VTE appear to be lower than previously reported, but remain elevated.