BackgroundInherited deficiency of the antithrombin (hereditary antithrombin deficiency, AT deficiency, OMIM #613118) is a relatively rare (1:2,000–3,000) autosomal-dominant disorder with high risk of venous thromboembolism. The molecular basis of this condition has not yet fully understood, highlighting the need for further research to elucidate the underlying pathological mechanisms.ObjectiveThis study aimed to investigate coagulation parameters and genetic phenotypes in a proband with hereditary antithrombin deficiency and her family members. Additionally, the investigation sought to provide preliminary insights for the molecular pathogenesis of this condition.MethodsBlood coagulation parameters, including plasma antithrombin activity (AT:A), antithrombin antigen (AT:Ag), protein C activity (PC:A), and protein S activity (PS:A) were measured in the peripheral blood of each family member by a Stago instrument. Peripheral blood was also extracted and sequenced to identify possible genetic mutation sites. The functional impact of variants on protein was subsequently analyzed by bioinformatics software.ResultsThe proband, her mother, and brother all exhibited decreased activity and antigen of AT but normal PC and PS activity. The proband's father had normal activity and antigen levels of AT, PC, and PS. Sequencing revealed the proband's mother inherited the SERPINC1:c.661T > C,p.(Trp221Arg) heterozygous variant and her father harbored PROC:c.572_574del,p.(Lys193del) heterozygous variant while the proband as well as her brother carried both. Conservation analysis revealed that Trp221 is highly conserved across homologous species. Bioinformatics tools consistently classify the p.Trp221Arg mutation as “pathogenic” or “deleterious.” Protein modeling indicated that the p.Trp221Arg variant does not alter the protein structure but may modify glycosylation sites to affect its function.ConclusionThe proband and family members exhibited varying degrees of decreased levels of AT and thrombosis, which were closely associated with inheritance of SERPINC1:c.661T > C,p.(Trp221Arg).

Coagulation Pediatric Reference Interval Study: Procoagulant Proteins Preliminary Findings

A positive association between antithrombin activity and selenium level has been reported. Selenoprotein P, the most important selenium carrier, was identified within human plasma fibrin clots. To investigate the relationship between selenoprotein P and antithrombin and its role in modulation of fibrin clot properties in antithrombin-deficient patients. Proteomic analysis of plasma fibrin clots was performed with mass spectrometry. In 108 patients with genetically confirmed type I (57%) or type II (43%) antithrombin deficiency and in healthy controls (n = 50), we assessed plasma selenoprotein P levels and thiobarbituric acid-reactive substances by enzyme-linked immunosorbent assay, along with fibrin clot permeability, clot lysis time, and thrombin generation. Clot-bound antithrombin concentration was 0.46 ± 0.32 mg/g protein, while selenoprotein P level was 30-fold lower (0.015 ± 0.012 mg/g). Type I compared to type II antithrombin-deficient patients had higher clot-bound antithrombin and selenoprotein P levels (both P < .001), associated together (ρ = 0.93, P < .001). Individuals with type I compared to type II antithrombin deficiency or controls had about 40% lower plasma selenoprotein P levels (P < .001). In antithrombin-deficient patients, plasma selenoprotein P was associated with antithrombin antigen (ρ = 0.35, P < .001) and thiobarbituric acid-reactive substances (ρ = 0.42, P < .001). Plasma selenoprotein P also correlated with endogenous thrombin potential (r = -0.33, P < .001), fibrin clot permeability (r = 0.43, P < .001), and clot lysis time (r = -0.40, P < .001) in antithrombin-deficient patients but not in controls. Patients with type I antithrombin deficiency had higher clot-bound selenoprotein P and reduced plasma selenoprotein P levels. Plasma selenoprotein P was associated with prothrombotic fibrin clot phenotype and enhanced thrombin generation.

External quality assessment (EQA) is used to evaluate laboratory performance in tests of hemostasis; however, some esoteric tests are performed by too few centers in any one EQA program to allow valid statistical assessment. To explore the feasibility of pooling data from several EQA providers, an exercise was carried out by the External Quality Assurance in Thrombosis and Haemostasis group, using the International Society on Thrombosis and Haemostasis Scientific and Standardization Committee (SSC) plasma standard for thrombophilia screening assays. Six EQA providers took part in this exercise, distributing the SSC plasma standard as a "blinded" sample to participants for thrombophilia tests between November 2020 and December 2021. Data were collected by each provider, anonymized, and pooled for analysis. Results were analyzed as overall results from each EQA provider, and by kit/method-specific comparisons of data from all providers pooled together. For each parameter, median results and range were determined. Over 1,250 sets of data were returned in the six EQA programs. The overall medians (all data pooled) were <4% of the assigned values for each parameter with the exception of protein C activity by clot-based assay. Method-related differences in median results were observed for free protein S antigen and protein S activity-a pattern seen across data from the different EQA providers. Antithrombin antigen results reported in mg/dL provided an example where small numbers of results for a single EQA provider may be supplemented by pooling data from multiple providers with good agreement seen among results reported by the different EQA providers. This study demonstrated that a multicenter EQA provider collaboration can be carried out and demonstrated benefit for assays with smaller number of participants. In addition, results showed good agreement with the assigned values of the SSC plasma standard. Further exercises for tests performed by only small numbers of laboratories can be planned.

To analyze the clinical phenotype and genetic characteristics of a Chinese pedigree affected with Hereditary antithrombin deficiency. A pedigree diagnosed at the the Second Affiliated Hospital of Wenzhou Medical University, Yuying Children's Hospital in June, 2020 was selected as the study subject. Plasma prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen (FIB), and thrombin time (TT) of the probands and their pedigree members were determined using a STA-R automatic coagulation analyzer. Antithrombin activity (AT: A) and antithrombin antigen (AT: Ag) in plasma were determined with chromogenic substrate and immunonephelometry assays. All exons and flanking sequences of the anticoagulant protein gene SERPINC1 were amplified by PCR and subjected to Sanger sequencing. Candidate variants were verified with bioinformatic tools (PolyPhen-2, SIFT, Mutation Taster and PYMOL) to explore their effect on the function and structural conformation of the protein. The probands (II-2, II-10), their brother (II-5) and sons (III-1, III-8) had shown normal PT, APTT, FIB, and TT, but significantly decreased AT: A and AT: Ag, with their levels being 34%, 57%, 56%, 48%, 53% and 13.51 mg/dL, 13.44 mg/dL, 18.39 mg/dL, 17.36 mg/dL, 17.71 mg/dL, respectively. The remaining pedigree members had normal values. Sanger sequencing revealed that the probands and all affected pedigree members had harbored a heterozygous c.851T>C (p.Met284Thr) missense variant in exon 5 of the SERPINC1 gene. Bioinformatic analysis and simulation suggested that the variant has resulted in alteration of hydrogen bonds at the c.851 position, which may affect the structure of the protein. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the variant was classified as pathogenic (PS1+PM1+PM5+PP1+PP4). The probands and other affected members were all diagnosed with type I hereditary AT deficiency, for which the c.851T>C (p.Met284Thr) variant of the SERPINC1 gene may be accountable.

Background Deficiency of antithrombin increases risk of venous thromboembolism. We hypothesized that antithrombin deficiency affects fibrin clot structure and function.Methods We evaluated 148 patients (age: 38 [32–50] years; 70% women) with genetically confirmed antithrombin deficiency and 50 healthy controls. Fibrin clot permeability (Ks) and clot lysis time (CLT) along with thrombin generation capacity were assessed before and after antithrombin activity normalization in vitro.Results Antithrombin-deficient patients had lower antithrombin activity (−39%) and antigen levels (−23%) compared with controls (bothp < 0.01). Prothrombin fragment 1 + 2 levels were 26.5% higher in patients with antithrombin deficiency than in controls along with 94% increased endogenous thrombin potential (ETP) and 108% higher peak thrombin (allp < 0.01). Antithrombin deficiency was associated with 18% reduced Ksand 35% prolonged CLT (bothp < 0.001). Patients with type I (n = 65; 43.9%) compared with type II antithrombin deficiency (n = 83; 56.1%) had 22.5% lower antithrombin activity (p < 0.001) and despite similar fibrinogen levels, 8.4% reduced Ks, 18% prolonged CLT, and 30% higher ETP (allp < 0.01). Reduced Kswas associated with lower antithrombin antigen level (β = − 6.1, 95% confidence interval [CI]: −1.7 to −10.5), while prolonged CLT was associated with lower antithrombin antigen (β = − 69.6, 95% CI: −9.6 to −129.7), activity (β = − 2.4, 95% CI: −0.3 to −4.5), higher PAI-1 (β = 12.1, 95% CI: 7.7–16.5), and thrombin-activatable fibrinolysis inhibitor levels (β = 3.8, 95% CI: 1.9–5.7). Addition of exogenous antithrombin reduced ETP (−42%) and peak thrombin (−21%), and improved Ks(+8%) and CLT (−12%; allp < 0.01).Conclusion Our study suggests that enhanced thrombin generation and prothrombotic plasma fibrin clot phenotype can contribute to increased risk of thrombosis in patients with antithrombin deficiency.

We performed in vitro experiments using whole human blood without anticoagulants to clarify the activity of anticoagulant proteins on membranes coated with acrylate-copolymer (ACP) with a hydrophilic blood-contacting layer compared to those coated by immobilizing heparin (IHP) in extracorporeal circulation. Whole human blood from healthy volunteers was recirculated in two types of experimental circuits with an ACP-coated reservoir and tubes and an ACP-coated or IHP-coated membrane. To compare the fluctuation of anticoagulant proteins, the circuit pressure at the inlet and outlet of the membrane was measured every 5min; antithrombin antigen (ATQ), antithrombin activity, protein-C quantitation (PCQ), protein-C activity, protein-S free antigen (PSQ), and protein-S activity were measured at 0, 30, 60, 120, and 180min in each experiment (n = 5). The time taken to achieve high circuit pressure (> 300mmHg) at the inlet of the membrane was significantly shorter in the ACP-coated membrane circuit (28 ± 2.7min) than in the IHP-coated membrane circuit (54 ± 24min); however, the ATQ, PCQ, and PSQ at 180min of recirculation were significantly higher in the former than in the latter (all p < .05). ACP-coated membranes can prevent the consumption of anticoagulant proteins but cannot delay circuit thrombogenicity compared to IHP-coated membranes. Considering patient care during the post-extracorporeal circulation period, the use of ACP coating, which can preserve anticoagulant protein, is better in extracorporeal circulation circuits.

Introduction : The etiology of ischemic stroke is heterogeneous, and it has been proposed that different stroke subtypes might have different genetic architecture 1,2. The plasminogen activator inhibitor‐1 (PAI‐1) has been of particular interest due to its role in thrombotic diseases. Several polymorphisms have been found for this gene, with some having protective effect while others increase the risk of ischemic and hemorrhagic strokes 3,4. The protective role appears to be due to the role of PAI‐1 in fibrinolytic cascade and that PAI‐1 also inhibit plasmin‐dependent metalloproteinases activation. We hereby, present a case of ischemic stroke in young adult and its association with our gene of interest. Methods : Case: We present a case of 43‐year‐old woman with past medical history significant for Acetylcholine Receptor (AChR) antibody positive Myasthenia Gravis diagnosed in 1993 status post thymectomy (1994), currently on prednisone and intravenous immunoglobulin every two weeks (failed cyclosporine and mycophenolate mofetil). She had two events in 2018 where she reported episodic right sided numbness and weakness that lasted for few hours. Stroke workup was done, and she was found to have focal moderate to severe stenosis of the left middle cerebral artery (MCA) on CT angiography (figure 1) with very subtle left hypoperfusion in the MCA on the brain single‐photon emission computerized tomography scan. She underwent catheter angiogram (figure 1) showing severe stenosis involving the mid and distal M1 segment of the left MCA and nondominant proximal A1 segment left anterior cerebral artery (ACA). There were robust leptomeningeal collaterals from the left anterior and left posterior cerebral arteries. She also reported history of two miscarriages in the first trimester. Hypercoagulable workup was done and all of those were negative including: SLE profile, Lupus anticoagulant, ANA comprehensive panel, Cryoglobulin, Anticardiolipin antibody, Antithrombin III, Antithrombin antigen, protein C, protein S, Factor VIII activity, Factor V Leiden. She also had rheumatoid arthritis factor, Homocysteine, sedimentation rate, and C‐reactive protein done which were unremarkable. Genetic workup showed that she is PAI‐1 5G/5G homozygous. She has been stable since 2018 without new focal neurological events and is on Aspirin monotherapy and Statin. Results : The genetics for stroke disease are very complicated and yet to be discovered fully. The association between PA‐1 5G/5G and intracranial stenosis has not been reported previously. New genetic associations will need to be increasingly considered as we assess our cerebrovascular diseases and stroke patients Conclusions : • With the current knowledge, ischemic stroke have polygenic basis but no single common “stroke gene” has been identified yet. • Here we present a case suggesting that PAI‐1 5G/5G genotype is may be associated with an independent risk of intracranial atherosclerosis.

Hereditary antithrombin deficiency is a rare autosomal-dominant disorder predisposing to recurrent venous thromboembolism (VTE). To date, only two founder mutations have been described. We investigated the antithrombin p.Thr147Ala variant, found in 12 patients of African origin. This variant is known as rs2227606 with minor allele frequency of 0.5% in Africans and absent in Europeans. A possible founder effect was investigated. Phenotypical characterization was established through immunological and functional methods, both under basal and stress conditions. Recombinant antithrombin molecules were constructed by site-directed mutagenesis and expressed in HEK-293T cells. Secreted antithrombin was purified and functionally characterized. Structural modeling was performed to predict the impact of the mutation on protein structure. A novel nanopore sequencing approach was used for haplotype investigation. Ten patients experienced VTE, stroke, or obstetric complications. Antithrombin antigen levels and anti-IIa activity were normal or slightly reduced while anti-Xa activity was reduced with only one commercial assay. On crossed immunoelectrophoresis, an increase of antithrombin fractions with reduced heparin affinity was observed under high ionic strength conditions but not under physiological conditions. The recombinant p.Thr147Ala protein displayed a reduced anti-Xa activity. Structural modeling revealed that residue Thr147 forms three hydrogen bonds that are abolished when mutated to alanine. The investigated patients shared a common haplotype involving 13 SERPINC1 intragenic single nucleotide polymorphisms. Antithrombin p.Thr147Ala, responsible for antithrombin type II heparin binding site deficiency, is the first founder mutation reported in people of African ancestry. This study further emphasizes the limitations of commercial methods to diagnose this specific subtype.

Predominant mutations in a hotspot of SERPINC1 associated with venous thromboembolism in the Chinese population: a case-control study

Hypercoagulability is a commonly described complication in patients with Cushing's syndrome. Recent clinical studies have indicated various abnormalities of coagulation and fibrinolysis parameters which may be related to that phenomenon. The aim of this study was to investigate the mechanisms underlying the hypercoagulable state in patients with Cushing's syndrome. A wide range of serum markers involved in the processes of blood coagulation and fibrinolysis was measured in a group of 33 patients with Cushing's syndrome and 31 healthy controls. No participant was taking medication which could influence the result or had known diseases, except hypertension and diabetes, which could affect blood coagulation or fibrinolysis parameters. Patients with Cushing's syndrome had higher levels of clotting factors II (P = 0.003), V (P < 0.001), VIII (P < 0.001), IX (P < 0.001), XI (P < 0.001) and XII (P = 0.019), protein C (P < 0.001), protein S (P < 0.001), C1-inhibitor (P < 0.001) and plasminogen activator inhibitor-1 (PAI-1) (P = 0.004). The activity of fibrinolytic markers, plasminogen (P < 0.001), antithrombin (P < 0.001) and antithrombin antigen (P = 0.001) was also increased in the patient group. The study has demonstrated hypercoagulability in patients with Cushing's syndrome manifest as increased prothrombotic activity and compensatory activation of the fibrinolytic system. We propose the introduction of thromboprophylaxis in the preoperative and early postoperative periods, combined with a close follow-up in order to prevent possible thromboembolic events in patients with Cushing's syndrome.

Role of Lipopolysaccharide and Cecal Ligation and Puncture on Blood Coagulation and Inflammation in Sensitive and Resistant Mice Models

Impairment of the protein C anticoagulation pathway is critical to the thrombosis associated with sepsis and to the development of purpura fulminans in meningococcemia. We studied the expression of thrombomodulin and the endothelial protein C receptor in the dermal microvasculature of children with severe meningococcemia and purpuric or petechial lesions. We assessed the integrity of the endothelium and the expression of thrombomodulin and the endothelial protein C receptor in biopsy specimens of purpuric lesions from 21 children with meningococcal sepsis (median age, 41 months), as compared with control skin-biopsy specimens. The expression of endothelial thrombomodulin and of the endothelial protein C receptor was lower in the patients with meningococcal sepsis than in the controls, both in vessels with thrombosis and in vessels without thrombosis. On electron microscopical examination, the endothelial cells were generally intact in both thrombosed and nonthrombosed vessels. Plasma thrombomodulin levels in the children with meningococcal sepsis (median, 6.4 ng per liter) were higher than those in the controls (median, 3.6 ng per liter; P=0.002). Plasma levels, protein C antigen, protein S antigen, and antithrombin antigen were lower than those in the controls. In two patients treated with unactivated protein C concentrate, activated protein C was undetectable at the time of admission, and plasma levels remained low. In severe meningococcal sepsis, protein C activation is impaired, a finding consistent with down-regulation of the endothelial thrombomodulin-endothelial protein C receptor pathway.

The effects of a low-dose monophasic preparation of levonorgestrel and ethinyl estradiol on coagulation and other hemostatic factors

Laboratory testing of antithrombin serves to demonstrate a decreased concentration that is indicative of a thrombotic tendency. We report unexpected high levels of antithrombin in a patient with hepatitis A. A 37-year-old woman with a 4-week history of acute hepatitis A was studied. The diagnosis of cholestatic hepatitis A was confirmed by positive serology and liver biopsy. The patient recovered completely within 6 months. Antithrombin activity was increased (234%; reference range, 80-120%). This high activity was confirmed by an antithrombin antigen of 210%. On recovery antithrombin activity returned to normal. We are unaware of other reports of such high levels of antithrombin, in particular in patients with hepatitis A. It is not clear whether the high concentration observed in this case is due to an acute-phase reaction or to impaired clearance by the liver. The presence of a molecular variant with different secretion characteristics is unlikely, since antithrombin activity returned to normal on recovery, suggesting base-line values within the normal range.

Patients with classical antithrombin deficiency (Type I) from seven unrelated kindreds were studied by crossed immunoelectrophoresis of plasma in the presence and absence of heparin. The only abnormal pattern was found in the kindred first reported by Egeberg in 1965. An abnormal cathodal peak of antithrombin antigen was found in the presence, but not the absence, of heparin in the first dimension gel. We have named this variant antithrombin Oslo. Such evidence of an abnormal protein, despite equivalent low levels of antithrombin antigen and activity, has been denoted previously by Sas as Type Ib deficiency. In the context of this new report, we review the literature to date on 33 other variants of the Types Ib, II and III subclassifications with a discussion of the value of the classification scheme.

Antithrombin antigen of high molecular weight associated with neoantigen in hemophilic plasma after factor IX concentrate therapy

A study of hemostasis in ischemic cerebrovascular disease: IV. A five year follow-up of some blood coagulation parameters also including fibrinopeptide A, factor XII and prekallikrein

A study of hemostasis in ischemic cerebrovascular disease I. Abnormalities in factor VIII and antithrombin