Antithrombin deficiency caused by SERPINC1 gene mutation in white matter lesions: A case report

RATIONALE

White matter lesions (WMLs) are structural changes in the brain that manifest as demyelination in the central nervous system pathologically. Vasogenic WMLs are the most prevalent type, primarily associated with advanced age and cerebrovascular risk factors. Conversely, immunogenic WMLs, typified by multiple sclerosis (MS), are more frequently observed in younger patients. It is crucial to distinguish between these 2 etiologies. Furthermore, in cases where multiple individuals exhibit WMLs within 1 family, genetic testing may offer a significant diagnostic perspective.

PATIENT CONCERNS

A 25-year-old male presented to the Department of Neurology with recurrent headaches. He was healthy previously and the neurological examination was negative. Brain magnetic resonance imaging (MRI) showed widespread white matter hyperintensity lesions surrounding the ventricles and subcortical regions on T2-weighted and T2 fluid-attenuated inversion recovery images, mimicking immunogenic disease-MS.

DIAGNOSES

The patient was diagnosed with a patent foramen ovale, which could explain his headache syndrome. Genetic testing unveiled a previously unidentified missense mutation in the SERPINC1 gene in the patient and his father. The specific abnormal laboratory finding was a reduction in antithrombin III activity, and the decrease may serve as the underlying cause for the presence of multiple intracranial WMLs observed in both the patient and his father.

INTERVENTIONS

The patient received percutaneous patent foramen ovale closure surgery and took antiplatelet drug recommended by cardiologists and was followed up for 1 month and 6 months after operation.

OUTCOMES

While the lesions on MRI remain unchanging during follow-up, the patient reported a significant relief in headaches compared to the initial presentation.

LESSONS

This case introduces a novel perspective on the etiology of cerebral WMLs, suggesting that hereditary antithrombin deficiency (ATD) could contribute to altered blood composition and may serve as an underlying cause in certain individuals with asymptomatic WMLs.

Epidemiology of anticoagulation for children supported by extracorporeal membrane oxygenation in the United States: A Pediatric Hospital Information System database study

INTRODUCTION

Due to the risk of thrombosis, nearly all children supported by extracorporeal membrane oxygenation (ECMO) receive systemic anticoagulation. While heparin has traditionally been used, there are reports of increased use of direct thrombin inhibitors. We sought to describe the use of anticoagulation in children supported by ECMO in the United States using a large administrative database.

METHODS

We performed a retrospective cohort study of children supported by ECMO within the Pediatric Health Information System (PHIS) database. Pediatric encounters involving ECMO from 2012 to 2020 were identified. Data regarding demographics, diagnoses, anticoagulation, complications, and outcomes were extracted for eligible encounters.

RESULTS

Eleven thousand five hundred ninety-five encounters that involved ECMO were identified. Fifty-four percent were male with an age range of 0-17 years and a median (IQR) age of 0 (0-2) years. Unfractionated heparin (UFH) only was used in 94% (95% CI: 93.6-94.5%) of encounters and UFH followed by bivalirudin in 5% (95% CI: 4.3-5.1%) of cases. There was a significant difference in the use of bivalirudin from 2012 to 2020 (p < 0.001). Differences in anticoagulation regimens were observed between infants and children (p = 0.004) and between those with and without cardiac indications for ECMO (p < 0.001). Four percent (95% CI: 4.1-4.8%) of encounters were associated with diagnostic coding for thrombosis and differences in occurrence of thrombosis were observed between different anticoagulant regimens (p < 0.001).

CONCLUSIONS

Though the majority of children on ECMO in the United States receive heparin anticoagulation, there is an increase in use of direct thrombin inhibitors. Prospective studies must evaluate the efficacy of different anticoagulants in this patient population.

Effect of prothrombin Belgrade mutation, causing antithrombin resistance, on fibrin clot properties

INTRODUCTION

Prothrombin Belgrade mutation is the result of the c.1787G>A substitution in the prothrombin gene. It is located in the antithrombin and sodium binding site and leads to impaired inactivation of thrombin by antithrombin, resulting in antithrombin resistance and thrombotic disorders. However, it negatively affects sodium binding and may have hypocoagulant effects. Considering that prothrombin Belgrade mutation mechanism is still not fully elucidated and that sodium binding is important for thrombin affinity towards fibrinogen, our aim was to determine whether this mutation affects fibrin clot formation and lysis.

METHODS

Using HEK293T cell line, recombinant wild type and mutated prothrombin were generated by transient transfection. Samples that correspond to plasma of a non-carrier, heterozygous and homozygous carriers were reconstituted using prothrombin deficient plasma and recombinant proteins. Reconstituted samples were used in OHP assay (Overall Hemostasis Potential) to determine kinetic profiles of coagulation and fibrinolysis. Clot turbidity assay was performed to observe kinetics of clot formation and lysis more closely. Fibrin clots formed in reconstituted plasma samples were analyzed by confocal microscopy to determine density of fibrin network. Fibrin clots were additionally observed using electron microscopy to determine thickness of individual fibrin fibers.

RESULTS

No significant difference found in OHP, OCP, OFP, and fibrin network density between wild type, heterozygous, and homozygous carrier reconstituted plasma samples. There were significant differences between samples for slope and slope time parameters in kinetic profiles and fibrin fiber thickness.

CONCLUSIONS

Results indicate that prothrombin Belgrade mutation has no significant impact on fibrinolysis, however it may affect kinetics of clot formation and its architecture.

[Phenotypic and genetic analysis of a Chinese pedigree affected with Hereditary antithrombin deficiency due to a novel variant of SERPINC1 gene]

OBJECTIVE

To analyze the clinical phenotype and genetic characteristics of a Chinese pedigree affected with Hereditary antithrombin deficiency.

METHODS

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.

RESULTS

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).

CONCLUSION

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.

Levels of procoagulant factors and peak thrombin generation in relation to dementia risk in older adults: The Cardiovascular Health Study

INTRODUCTION

Markers of hemostasis such as procoagulant factors and peak thrombin generation are associated with cardiovascular outcomes, but their associations with dementia risk are unclear. We aimed to evaluate prospective associations of selected procoagulant factors and peak thrombin generation with dementia risk.

METHODS

We measured levels of 7 hemostatic factors (fibrinogen, factor VII coagulant activity [FVIIc], activated factor VII [FVIIa], factor VIIa-antithrombin [FVIIa-AT], factor XI antigen [FXI], peak thrombin generation, and platelet count) among participants in the Cardiovascular Health Study, a cohort of older adults free of dementia in 1992/1993 (n = 3185). Dementia was adjudicated and classified by DSM-IV criteria through 1998/1999. Cox proportional hazards models estimated hazard ratios (HRs) for any dementia associated with 1-standard deviation (SD) differences, adjusting for sociodemographic and clinical factors and APOE genotype. Secondary analyses separately evaluated the risk of vascular dementia, Alzheimer's disease, and mixed dementia.

RESULTS

At baseline, participants had a median age of 73 years. Over 5.4 years of follow-up, we identified 448 dementia cases. There was no evidence of linear associations between levels of these hemostatic factors with any dementia risk (HRs per 1-SD difference ranged from 1.0 to 1.1; 95 % confidence intervals included 1.0). Results of secondary analyses by dementia subtype were similar.

CONCLUSIONS

In this prospective study, there was no strong evidence of linear associations between levels of fibrinogen, FVIIc, FVIIa, FVIIa-AT, FXI, peak thrombin generation, or platelet count with dementia risk. Despite their associations with cardiovascular disease, higher levels of these biomarkers measured among older adults may not reflect dementia risk.

The clinical and genetic landscape of early-onset thrombophilia in Japan

OBJECTIVES

To determine the optimal management for early-onset thrombophilia (EOT), the genetic and clinical features of protein C (PC)-, protein S (PS)-, or antithrombin (AT)-deficient patients of ≤20 years of age were studied in Japan.

METHODS/RESULTS

Clinical and genetic information of all genetically diagnosed cases was collected through the prospective, retrospective study, and literature review. One-hundred-one patients had PC (n = 55), PS (n = 29), or AT deficiency (n = 18). One overlapping case had PC- and PS-monoallelic variant. Fifty-five PC-deficient patients (54%) had 26 monoallelic or 29 biallelic variant(s), and 29 (29%) PS-deficient patients had 20 monoallelic or nine biallelic variant(s). None of the patients had AT-biallelic variants. The frequent low-risk allele p.K193del (PC-Tottori) was found in five patients with monoallelic (19%) but not 29 with biallelic variant(s). The most common low-risk allele p.K196E (PS-Tokushima) was found in five with monoallelic (25%) and six with biallelic variant(s) (67%). One exceptional de novo PC variant was found in 32 families with EOT. Only five parents had a history of thromboembolism. Thrombosis concurrently developed in three mother-newborn pairs (two PC deficiency and one AT deficiency). The prospective cohort revealed the outcomes of 35 patients: three deaths with PC deficiency and 20 complication-free survivors. Neurological complications were more frequently found in patients with PC-biallelic variants than those with PC-, PS-, or AT-monoallelic variants (73% vs. 24%, p = .019).

CONCLUSIONS

We demonstrate the need for elective screening for EOT targeting PC deficiency in Japan. Early prenatal diagnosis of PC deficiency in mother-infant pairs may prevent perinatal thrombosis in them.

A metabolomics discrimination-based strategy for screening the antithrombin active markers of perilla seeds: A natural oil crop

Natural crops oil with high nutritional value has gradually attracted attention. Perilla seeds are regarded as a source of functional edible oil in America, Asia and European countries due to its abundant nutrients. In this research, samples were extracted by different polarity solvents and evaluated their thrombin inhibition activities in vitro. Metabolomics combined with chemometrics revealed the antithrombin active markers of perilla seeds. The enzyme kinetics and molecular docking results were useful in clarifying their inhibition of thrombin. The orthogonal experimental design was applied to optimize the extraction process of six antithrombin active markers from perilla seeds. The results showed that rosmarinic acid, luteolin, luteolin-7-O-glucoside, α-linolenic acid, linoleic acid, and oleic acid were screened out as functional and active markers. Besides, perilla seeds as a natural oil crop had the potential of antithrombin. It can also be applied in the food field because of its nutraceutical functions. Metabolomics combined with chemometrics will facilitate the discovery of functional, active markers in perilla seeds, which is conducive to accurate quality control.

Antithrombin activity and central venous catheter-associated thrombosis in critically ill children at high risk of bleeding

BACKGROUND

Normalization of antithrombin activity may prevent catheter-associated thrombosis in critically ill children at high risk of bleeding.

OBJECTIVES

To characterize the temporal pattern of antithrombin activity, assess its association with catheter-associated thrombosis and clinically relevant bleeding, and evaluate its relationship with thrombin generation in these children.

METHODS

In this prospective cohort study, critically ill children <18 years old at high risk of bleeding with central venous catheter were eligible. Antithrombin activity and thrombin generation were measured from platelet-poor plasma and after in vitro antithrombin supplementation. Systematic surveillance ultrasound was performed to diagnose thrombosis. Children were followed for bleeding.

RESULTS

We enrolled 8 infants (median age: 0.2 years, IQR: 0.2, 0.3 years) and 72 older children (median age: 14.3 years, IQR: 9.1, 16.1 years). Mean antithrombin on the day of catheter insertion was 64 IU/dL (SD: 32 IU/dL) in infants and 83 IU/dL (SD: 35 IU/dL) in older children. Antithrombin normalized by the day of catheter removal. Thrombosis developed in 27 children, while 31 children bled. Thrombosis (regression coefficient: 0.008, 95% CI: -0.01, 0.03) and bleeding (regression coefficient: -0.0007, 95% CI: -0.02, 0.02) were not associated with antithrombin. Antithrombin was not correlated with in vivo change in endogenous thrombin potential (correlation coefficient: -0.07, 95% CI: -0.21, 0.08). In vitro supplementation reduced endogenous thrombin potential (correlation coefficient: -0.78; 95% CI: -0.95, -0.23).

CONCLUSION

These findings may not support normalization of antithrombin activity to prevent catheter-associated thrombosis in critically ill children at high risk of bleeding.

The interplay between tamoxifen and endoxifen plasma concentrations and coagulation parameters in patients with primary breast cancer

BACKGROUND

Tamoxifen is an effective treatment for primary breast cancer but increases the risk for venous thromboembolism. Tamoxifen decreases anticoagulant proteins, including antithrombin (AT), protein C (PC) and tissue factor (TF) pathway inhibitor, and enhances thrombin generation (TG). However, the relation between plasma concentrations of both tamoxifen and its active metabolite endoxifen and coagulation remains unknown.

METHODS

Tamoxifen and endoxifen were measured in 141 patients from the prospective open-label intervention TOTAM-study after 3 months (m) and 6 m of tamoxifen treatment. Levels of AT and PC, the procoagulant TF, and TG parameters were determined at both timepoints if samples were available (n = 53-135 per analysis). Levels of coagulation proteins and TG parameters were correlated and compared between: 1) quartiles of tamoxifen and endoxifen levels, and 2) 3 m and 6 m of treatment.

RESULTS

At 3 m, levels of AT, PC, TF and TG parameters were not associated with tamoxifen nor endoxifen levels. At 6 m, median TF levels were lower in patients in the 3rd (56.6 [33] pg/mL), and 4th (50.1 [19] pg/mL) endoxifen quartiles compared to the 1st (lowest) quartile (76 [69] pg/mL) (P=0.027 and P=0.018, respectively), but no differences in anticoagulant proteins or TG parameters were observed. An increase in circulating TF levels (3 m: 46.0 [15] versus 6 m: 54.4 [39] pg/mL, P < 0.001) and TG parameters was observed at the 6 m treatment timepoint, while AT and PC levels remained stable.

CONCLUSIONS

Our results indicate that higher tamoxifen and endoxifen levels are not correlated with an increased procoagulant state, suggesting tamoxifen dose escalation does not further promote hypercoagulability.

Increased contact activated endogenous thrombin potential in pregnant women with preeclampsia

Preeclampsia is a worldwide contributor to maternal and fetal morbidity and mortality. Women with preeclampsia are in a hyper-coagulable state with increased risk of thromboembolic disease later in life compared with normal pregnant women. The contact system (CAS) in plasma can mediate thrombin generation and is an important contributor to thrombus growth, but the activation of CAS during pregnancy complicated by preeclampsia is not yet elucidated, and CAS may play a role in the pathophysiology of preeclampsia. Therefore, the aim of the study is to address thrombin generation, and in particular, the capacity of the CAS-mediated pathway in patients with preeclampsia compared with pregnant controls. One hundred and seventeen women with preeclampsia and matched controls were included. The project was registered at www.clinicaltrials.gov as NCT04825145. CAS and tissue factor induced thrombin generation, proteins C and S, antithrombin, and histidine-rich glycoprotein (HRG) were assessed. Women with preeclampsia had significantly increased CAS and tissue factor-induced endogenous thrombin potential (ETP), and HRG compared with controls, P  = 0.022, P  = 0.024, and P  = 0.02, respectively. The concentrations of protein C and antithrombin were significantly reduced in the preeclampsia group, P  = 0.024 and P  < 0.0001, respectively. No significant difference in the concentration of protein S was detected, P  = 0.06. This study demonstrates a significant increased CAS-induced ETP and an overall decrease of important regulators of coagulation in women with preeclampsia compared with controls. These aspects can contribute to the hyper-coagulable state characterizing preeclampsia.

Association between acute complications in PMM2-CDG patients and haemostasis anomalies: Data from a multicentric study and suggestions for acute management

OBJECTIVES

Patients with PMM2-CDG develop acute events (stroke-like episodes (SLEs), thromboses, haemorrhages, seizures, migraines) associated with both clotting factors (factor XI) and coagulation inhibitors (antithrombin, protein C and protein S) deficiencies. The aim of the study was to correlate acute events to haemostasis and propose practical guidelines.

METHODS

In this multicentric retrospective study, we evaluated clinical, radiological, haemostasis and electroencephalography data for PMM2-CDG patients hospitalized for acute events. Cerebral events were classified as thrombosis, haemorrhage, SLE, or "stroke mimic" (SM: normal brain imaging or evoking a migraine).

RESULTS

Thirteen patients had a total of 31 acute episodes: 27 cerebral events with 7 SLEs, 4 venous thromboses, 4 haemorrhages (3 associated with thrombosis), 15 SMs at a mean age of 7.7 years; 4 non-cerebral thromboses, one of which included bleeding. A trigger was frequently involved (infection, head trauma). Although sometimes normal at baseline state, factor XI, antithrombin and protein C levels decreased during these episodes. No correlation between haemostasis anomalies and type of acute event was found.

DISCUSSION

Acute events in PMM2-CDG are not negligible and are associated with haemostasis anomalies. An emergency protocol is proposed for their prevention and treatment (https://www.filiere-g2m.fr/urgences). For cerebral events, brain Magnetic Resonance Imaging with perfusion weight imaging and diffusion sequences, electroencephalogram and haemostasis protein levels guide the treatment: anticoagulation, antithrombin or fresh frozen plasma supplementation, antiepileptic therapy. Preventing bleeding and thrombosis is required in cases of surgery, prolonged immobilization, hormone replacement therapy.

CONCLUSION

Acute events in PMM2-CDG are associated with abnormal haemostasis, requiring practical guidance.

Endothelial dysfunction, thrombophilia, and nailfold capillaroscopic features in livedoid vasculopathy

BACKGROUND

Livedoid vasculopathy (LV) is a rare, disabling disease characterized by painful ulcers, livedo reticularis and atrophy blanche. Hypercoagulation, endothelial, and microcirculatory dysfunction are believed to be responsible for the pathogenesis of this difficult-to-treat disease.

OBJECTIVES

This study sought to investigate the frequency of endothelial dysfunction, hypercoagulability, and nailfold capillaroscopic features in LV patients to shed light on its etiology.

METHODS

This case-control study included 16 patients with LV, 24 with systemic sclerosis (SSc), and 23 control subjects. Serum markers of endothelial dysfunction soluble endoglin, endocan, endothelin-1, lipoprotein a, plasminogen activator inhibitor-1 (PAI-1), soluble thrombomodulin, and von Willebrand factor were measured using enzyme-linked immunosorbent assays. Flow-mediated dilation and carotid intima-media thickness were examined as markers of endothelial dysfunction, and microcirculation was assessed with nailfold capillaroscopy. Thrombophilia-related parameters, including gene polymorphisms of factor V Leiden, prothrombin, PAI-1 genes, methylenetetrahydrofolate reductase (MTHFR) and factor XIII mutation and serum levels of protein C, protein S, antithrombin, homocysteine, D-dimer and antiphospholipid antibodies were investigated in LV patients.

RESULTS

Plasminogen activator inhibitor-1 and soluble thrombomodulin levels were significantly higher in LV patients compared to control subjects (2.3 [2.05-2.79] ng/ml vs. 1.89 [1.43-2.33] ng/ml, p = 0.007; 1.15 [0.88-1.4] ng/ml vs. 0.76 [0.56-0.9] ng/ml, p = 0.004, respectively). Flow-mediated dilation was 25.4 % lower in the LV patients compared to the control group (14.77 % [11.26-18.26] vs. 19.80 % [16.47-24.88], p = 0.034). Capillaroscopic features, including ramifications (75 % vs. 8.7 %, p < 0.001), avascular areas (25 % vs. 0 %, p = 0.011) and dilatations (33.2 % vs. 0 %, p = 0.016), were significantly higher in LV patients than in controls. LV patients had multiple biochemical or genetic abnormalities related to thrombophilia, including heterozygous factor V Leiden mutations (6.3 %), MTHFR (C677T) mutations (heterozygous 43.8 %, homozygous 18.8 %), MTHFR (A1298C) mutations (heterozygous 37.5 %, homozygous 12.5 %), factor XIII heterozygous mutation (12.5 %), antithrombin deficiency (31.3 %), protein S deficiency (12.5 %), hyperhomocysteinemia (31.3 %), D-dimer elevation (25 %), anti-β2-glycoprotein I (12.5 %), lupus anticoagulant antibodies (6.3 %), and anticardiolipin antibodies (6.3 %).

CONCLUSIONS

In conclusion, LV patients were characterized by an increased presence of thrombophilia-related parameters, and also exhibited vascular endothelial and microcirculatory dysfunction, resembling SSc. These findings support the complex interaction of thrombophilia, endothelial dysfunction, and microcirculation dysregulation in the pathogenesis of LV. Thus, the treatment of LV patients should be individualized, based on the identification of the predominant pathological pathways.

Protein C and protein S deficiencies are associated with increased risk of deep vein thrombosis in pregnant women using oral contraceptives

BACKGROUND

Oral contraceptives are commonly taken by women and are known to increase the risk of venous thromboembolism (VTE).

OBJECTIVE

The aim of this study was to investigate the association between oral contraceptive use and natural anticoagulants, that is, protein C (PC), protein S (PS), and antithrombin in pregnant women with deep vein thrombosis (DVT).

MATERIALS AND METHODS

This case-control study was conducted on 330 pregnant women, that is, cases 165 (who used oral contraceptives) and controls 165 (who did not use oral contraceptives). The levels of PC, PS, and antithrombin were measured and compared between the two groups. The use of different types of oral contraceptives and their association with DVT and PC and PS were also analyzed.

RESULTS

The study found that women with DVT had significantly lower levels of PC and PS compared with controls ( P  < 0.001). However, no significant difference was found in the levels of AT. Among the different types of oral contraceptives, first-generation progestin pills including Ethynodiol Diacetate, Norethindrone Acetate, Norethynodrel, and second-generation oral contraceptives (Lynestrenol, Levonorgestrel and Norgestrel) were not found to be associated with lower levels of PC and AT while Desogestrel, Norgestimate, and Gestodene (third-generation) were associated with lower levels of PS.

CONCLUSION

This study suggests that the use of contraceptives, particularly those containing Desogestrel, Norgestimate, and Gestodene, may be associated with a higher risk of thrombosis because of the associated lower levels of PS. Monitoring anticoagulant levels is crucial in preventing DVT in this population.

Functional analysis of two abnormal antithrombin proteins with different intracellular kinetics

INTRODUCTION

Hereditary antithrombin (AT) deficiency type I causes venous thrombosis due to decreased levels of AT antigen in the blood. We identified one novel and one known abnormal variant in two unrelated Japanese families with venous thrombosis. In this study, we analyzed the mechanism by which these abnormal variants cause type I AT deficiency.

MATERIALS AND METHODS

Wild-type and variant AT expression vectors were constructed and transiently expressed in human embryonic kidney 293 cells, and AT antigen levels and N-glycosylation of cell lysates and culture medium were evaluated by western blot analysis. Subcellular co-localization of AT was also examined using confocal microscopy, and chase experiments with cycloheximide and MG132 were performed to investigate the degradation pathway of AT variants.

RESULTS

Genetic analysis identified a novel variant, c.613delC (p.Leu205Trpfs⁎79), and the known variant c.283T>C (p.Tyr95His). These AT variants exhibited significantly reduced extracellular secretion compared with the wild-type; N-glycosylation of the AT protein was normal. Co-localization analysis suggested that the transport of these abnormal AT proteins to the Golgi apparatus was impaired. The c.613delC variant was degraded early by the proteasome, suggesting that the c.283T>C variant is stored in the endoplasmic reticulum (ER).

CONCLUSIONS

The AT variants identified here synthesize abnormal AT proteins that exhibit suppressed secretion and impaired transport from the ER to the Golgi apparatus. These results provide clues that could help elucidate the mechanism of type I AT deficiency and facilitate therapy development.

Antithrombin Deficiency Is Associated with Prothrombotic Plasma Fibrin Clot Phenotype

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 (both p < 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 (all p < 0.01). Antithrombin deficiency was associated with 18% reduced Ks and 35% prolonged CLT (both p < 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 (all p < 0.01). Reduced Ks was 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%; all p < 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.

Laboratory Evaluation of Antithrombin, Protein C, and Protein S

Thrombophilia is a complex disease process, clinically manifesting in various forms of venous thromboembolism. Although both genetic and acquired (or environmental) risks factors have been reported, the presence of a genetic defect (antithrombin [AT], protein C [PC], protein S [PS]) is considered three of the major contributing factors of thrombophilia. The presence of each of these risk factors can be established by clinical laboratory analysis; however, the clinical provider and laboratory personnel must understand the testing limitations and shortcomings associated with the assays for these factors to be able to ensure an accurate diagnosis. This article will describe the major pre-analytical, analytical, and post-analytical issues associated with the various types of assays and discuss evidence-based algorithms for analyzing AT, PC, and PS in plasma.

Paraprotein associated heparin resistance during cardiopulmonary bypass

INTRODUCTION

Heparin resistance during cardiopulmonary bypass poses a significant intraoperative dilemma. Antithrombin deficiency related heparin resistance is well described, but less common causes are still poorly understood and inadequately managed.

CASE REPORT

We present a case of heparin resistance during cardiopulmonary bypass in a gentleman with no previous haematological history or thrombotic risk factors. The patient required three times the regular dose of unfractionated heparin to achieve acceptable conditions to initiate and maintain bypass. The patient was found to have elevated serum immunoglobulin M (IgM) kappa paraprotein on post-operative investigation.

DISCUSSION

Paraproteins may exhibit non-specific binding to long polymeric chains of unfractionated heparin and inhibits the interaction between heparin and antithrombin. As a result, excessive doses of heparin are required to overcome this, which increases the risk of perioperative bleeding and other complications.

CONCLUSION

Elevated serum paraprotein levels should be recognised as a cause of heparin resistance during cardiopulmonary bypass.

Antithrombin, Protein C, and Protein S: Genome and Transcriptome-Wide Association Studies Identify 7 Novel Loci Regulating Plasma Levels

BACKGROUND

Antithrombin, PC (protein C), and PS (protein S) are circulating natural anticoagulant proteins that regulate hemostasis and of which partial deficiencies are causes of venous thromboembolism. Previous genetic association studies involving antithrombin, PC, and PS were limited by modest sample sizes or by being restricted to candidate genes. In the setting of the Cohorts for Heart and Aging Research in Genomic Epidemiology consortium, we meta-analyzed across ancestries the results from 10 genome-wide association studies of plasma levels of antithrombin, PC, PS free, and PS total.

METHODS

Study participants were of European and African ancestries, and genotype data were imputed to TOPMed, a dense multiancestry reference panel. Each of the 10 studies conducted a genome-wide association studies for each phenotype and summary results were meta-analyzed, stratified by ancestry. Analysis of antithrombin included 25 243 European ancestry and 2688 African ancestry participants, PC analysis included 16 597 European ancestry and 2688 African ancestry participants, PSF and PST analysis included 4113 and 6409 European ancestry participants. We also conducted transcriptome-wide association analyses and multiphenotype analysis to discover additional associations. Novel genome-wide association studies and transcriptome-wide association analyses findings were validated by in vitro functional experiments. Mendelian randomization was performed to assess the causal relationship between these proteins and cardiovascular outcomes.

RESULTS

Genome-wide association studies meta-analyses identified 4 newly associated loci: 3 with antithrombin levels (GCKR, BAZ1B, and HP-TXNL4B) and 1 with PS levels (ORM1-ORM2). transcriptome-wide association analyses identified 3 newly associated genes: 1 with antithrombin level (FCGRT), 1 with PC (GOLM2), and 1 with PS (MYL7). In addition, we replicated 7 independent loci reported in previous studies. Functional experiments provided evidence for the involvement of GCKR, SNX17, and HP genes in antithrombin regulation.

CONCLUSIONS

The use of larger sample sizes, diverse populations, and a denser imputation reference panel allowed the detection of 7 novel genomic loci associated with plasma antithrombin, PC, and PS levels.

Thrombin-mediated activation of PAR1 enhances doxorubicin-induced cardiac injury in mice

The chemotherapeutic drug doxorubicin is cardiotoxic and can cause irreversible heart failure. In addition to being cardiotoxic, doxorubicin also induces the activation of coagulation. We determined the effect of thrombin-mediated activation of protease-activated receptor 1 (PAR1) on doxorubicin-induced cardiac injury. Administration of doxorubicin to mice resulted in a significant increase in plasma prothrombin fragment 1+2, thrombin-antithrombin complexes, and extracellular vesicle tissue factor activity. Doxorubicin-treated mice expressing low levels of tissue factor, but not factor XII-deficient mice, had reduced plasma thrombin-antithrombin complexes compared to controls. To evaluate the role of thrombin-mediated activation of PAR1, transgenic mice insensitive to thrombin (Par1R41Q) or activated protein C (Par1R46Q) were subjected to acute and chronic models of doxorubicin-induced cardiac injury and compared with Par1 wild-type (Par1+/+) and PAR1 deficient (Par1-/-) mice. Par1R41Q and Par1-/- mice, but not Par1R46Q mice, demonstrated similar reductions in the cardiac injury marker cardiac troponin I, preserved cardiac function, and reduced cardiac fibrosis compared to Par1+/+ controls after administration of doxorubicin. Furthermore, inhibition of Gαq signaling downstream of PAR1 with the small molecule inhibitor Q94 significantly preserved cardiac function in Par1+/+ mice, but not in Par1R41Q mice subjected to the acute model of cardiac injury when compared to vehicle controls. In addition, mice with PAR1 deleted in either cardiomyocytes or cardiac fibroblasts demonstrated reduced cardiac injury compared to controls. Taken together, these data suggest that thrombin-mediated activation of PAR1 contributes to doxorubicin-induced cardiac injury.

Recommendation on the nomenclature for anticoagulants: updated communication from the International Society on Thrombosis and Haemostasis Scientific and Standardization Commitee on the Control of Anticoagulation

Oral anticoagulation therapy has evolved beyond vitamin K antagonists to include oral direct thrombin inhibitors and factor Xa inhibitors. Collectively known as "direct oral anticoagulants," this class of medications represents the current standard of care for the prevention and treatment of common thrombotic disorders, including atrial fibrillation and venous thromboembolism. Medications that target factors XI/XIa and XII/XIIa are currently under investigation for several thrombotic and nonthrombotic conditions. Given that these emerging medications will likely have distinct risk-benefit profiles to the current direct oral anticoagulants, may have different routes of administration, and could be used for unique clinical conditions (e.g., hereditary angioedema), the International Society on Thrombosis and Haemostasis Subcommittee on Control of Anticoagulation assembled a writing group to make recommendations on the nomenclature of anticoagulant medications. With input from the broader thrombosis community, the writing group recommends that anticoagulant medications be described by the route of administration and specific targets (e.g., oral factor XIa inhibitor).

Hemostatic profiles in dogs with sudden acquired retinal degeneration syndrome

BACKGROUND

Sudden acquired retinal degeneration syndrome (SARDS) is a common cause of irreversible blindness in dogs. It bears clinical resemblance to hypercortisolism, which can be associated with hypercoagulability. The role of hypercoagulability in dogs with SARDS is unknown.

OBJECTIVE

Determine hemostatic profiles in dogs with SARDS.

ANIMALS

Prospective pilot study: Dogs with a history of SARDS (n = 12). Prospective case-control study: Dogs with recent onset of SARDS (n = 7) and age-, breed-, and sex-matched controls (n = 7).

METHODS

Prospective pilot study: We performed thromboelastography (TEG). Prospective case-control study: Dogs had CBC, serum biochemistry, urinalysis, TEG, fibrinogen concentration, antithrombin activity, D-dimers, thrombin-antithrombin complexes, and optical platelet aggregometry performed.

RESULTS

Prospective pilot study: 9/12 dogs with a history of SARDS were hypercoagulable with increased TEG G value and 2/3 had hyperfibrinogenemia. Case-control study: All dogs with SARDS and 5/7 controls were hypercoagulable based on TEG G value. Dogs with SARDS had significantly higher G values (median, 12.7 kdynes/s; range, 11.2-25.4; P = .04) and plasma fibrinogen concentration (median, 463 mg/dL; range, 391-680; P < .001) compared to controls.

CONCLUSIONS AND CLINICAL IMPORTANCE

Hypercoagulability was common in both dogs with SARDS and controls, but dogs with SARDS were significantly more hypercoagulable on TEG. The role of hypercoagulability in the pathogenesis of SARDS remains to be determined.

Peripartum management of deep venous thrombosis in the context of antithrombin deficiency and May-Thurner syndrome

Literature regarding the management of thrombus refractory to first-line treatment in the setting of pregnancy is limited, and management is made even more complicated in the context of thrombophilia. This case reviews the management of a patient with antithrombin deficiency who developed a massive thrombus during pregnancy, which was complicated by May-Thurner syndrome, lack of improvement with heparin, and preterm labor. The patient received multidisciplinary care throughout the pregnancy. At 35 weeks, anticoagulation was paused as she underwent induction of labor and delivery followed by postpartum placement of inferior vena cava filter and restarting heparin. Successful management of our pregnant patient with thrombus refractory to heparin hinged on individualized treatment for medical optimization with anticoagulation and antithrombin concentrate prior to labor followed by immediate postpartum placement of inferior vena cava filter.

Three Cases of Unprovoked Venous Thromboembolism with Prothrombin p.Arg596Gln Variant and a Literature Review of Antithrombin Resistance

Antithrombin resistance (ATR) is a newly identified strong genetic predisposition to venous thromboembolism (VTE) caused by genetic variations in prothrombin with substitutions of Arg at position 596 with either Leu, Gln, or Trp. In the present report, we identified a missense variant p.Arg596Gln in 3 patients from 2 families with unprovoked VTE who each experienced their first VTE event at 19, 67, and 19 years old. The three patients did not show any positive markers for thrombophilia on routine testing, suggesting that patients with unprovoked VTE who have negative findings on thrombophilia tests may carry a prothrombin variant with ATR.

Usefulness and Limitations of Multiple Ligation-Dependent Probe Amplification in Antithrombin Deficiency

Multiplex ligation-dependent probe amplification (MLPA) identifies genetic structural variants in SERPINC1 in 5% of cases with antithrombin deficiency (ATD), the most severe congenital thrombophilia. Our aim was to unravel the utility and limitations of MLPA in a large cohort of unrelated patients with ATD (N = 341). MLPA identified 22 structural variants (SVs) causing ATD (6.5%). MLPA did not detect SVs affecting introns (four cases), and the diagnosis was inaccurate in two cases according to long-range PCR or nanopore sequencing. MLPA was used to detect possible hidden SVs in 61 cases with type I deficiency with single nucleotide variations (SNVs) or small insertion/deletion (INDEL). One case had a false deletion of exon 7, as the 29-bp deletion affected an MLPA probe. We evaluated 32 variants affecting MLPA probes: 27 SNVs and 5 small INDELs. In three cases, MLPA gave false-positive results, all diagnosed as deletions of the affected exon: a small INDEL complex, and two SNVs affecting MLPA probes. Our study confirms the utility of MLPA to detect SVs in ATD, but also shows some limitations in detecting intronic SVs. MLPA renders imprecise and false-positive results for genetic defects which affect MLPA probes. Our results encourage the validation of MLPA results.

Performance evaluation of the Sysmex CN-6000-automated coagulation analyzers for routine coagulation tests

The Sysmex CN-6000 is a novel automated multiparameter coagulometer that performs clotting, chromogenic and immunological assays, and platelet aggregation tests in a single system. Here we evaluated its performance of routine coagulation assays. The precision, linearity, carryover and establishment of reference ranges of the CN-6000, as well as correlations between it and the currently used Diagnostica Stago STA-R Max were determined according to Clinical and Laboratory Standards Institute guidelines. The evaluated parameters included prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen (FBG), antithrombin (AT), d-dimers (DDi), and fibrin and FBG degradation products (FDP). The intra-run and inter-run precisions of the six tests were determined using normal and pathological control materials; all coefficients of variation were acceptable and within the allowable ranges. The CN-6000 showed excellent linearity for FBG, AT, DDi, and FDP (R = 0.999-1.00). Passing-Bablok regression (R2 > 0.95) demonstrated good agreement between the analyzers. In the carryover study, APTT, PT, FBG, AT, DDi, and FDP values were all acceptable. The establishing reference intervals revealed that each manufacturer's range was acceptable. Significant differences were observed in the APTT reference range because of using different detection systems and reagents. The CN-6000 analyzer showed reliable performance and good correlation with the currently used STA-R Max automated hemostatic analyzer. As CN-6000 uses an optical clot-detection method, its reference ranges for PT and APTT are lower than those of the STA-R Max; thus, the difference should be considered before its use.

Exploring the Role of Antithrombin in Nephrotic Syndrome-Associated Hypercoagulopathy: A Multi-Cohort Study and Meta-Analysis

BACKGROUND

Nephrotic syndrome is associated with an acquired hypercoagulopathy that is thought to drive its predisposition for venous thromboembolism. Previous studies have suggested that urinary antithrombin (AT) loss leading to acquired AT deficiency is the primary mechanism underlying this hypercoagulopathy, but this hypothesis has not been directly tested. The objectives of this study were to test the influence of AT levels on hypercoagulopathy in nephrotic syndrome patient samples and perform meta-analyses to evaluate the likelihood of AT deficiency in patients with nephrotic syndrome.

METHODS

Samples from three independent nephrotic syndrome cohorts were analyzed. AT antigen and activity assays were performed using ELISA and amidolytic assays, respectively. Plasma thrombin generation, albumin, and urine protein-to-creatinine ratios were determined using established methods. Meta-analyses were performed by combining these new data with previously published data.

RESULTS

AT levels were not consistently related to either plasma albumin or proteinuria. AT was quantitatively related to hypercoagulopathy in adult nephrotic syndrome, whereas AT activity was inconsistently associated with hypercoagulopathy in childhood nephrotic syndrome. Notably, hypercoagulopathy did not differ between patients with normal AT levels and those with levels below the threshold used to define clinical AT deficiency (<70%). Moreover, ex vivo AT supplementation did not significantly alter hypercoagulopathy in AT-deficient plasma samples. The meta-analyses demonstrated that AT deficiency was not a uniform feature of nephrotic syndrome and was more common in children than adults.

CONCLUSIONS

These data suggest that AT deficiency plays only a limited role in the mechanisms underlying the acquired hypercoagulopathy of nephrotic syndrome. Moreover, AT deficiency was not present in all patients with nephrotic syndrome and was more likely in children than adults despite the higher risk for venous thromboembolism in adults than children.

Prognostic Value of Antithrombin Activity Levels in the Early Phase of Intensive Care: A 2-Center Retrospective Cohort Study

To investigate the relationship between antithrombin (AT) activity level and prognosis in patients requiring intensive care. Patients whose AT activity was measured within 24 h of intensive care unit (ICU) admission were enrolled for analysis. The primary endpoint was mortality at discharge. Prognostic accuracy was examined using receiver operating characteristic (ROC) curves and cox hazard regression analysis. Patients were divided into 6 groups based on predicted mortality, and a χ2 independence test was performed on the prognostic value of AT activity for each predicted mortality; P < .05 was considered significant. A total of 281 cases were analyzed. AT activity was associated with mortality at discharge (AT% [interquartile range, IQR]): survivor group, 69 (56-86) versus nonsurvivor group, 56 (44-73), P = .0003). We found an increasing risk for mortality in both the lowest level of AT activity (<50%; hazard ratio [HR] 2.43, 95% confidence interval [CI] 1.20-4.89, P = .01) and the middle-low level of AT activity (≥ 50% and < 70%; HR 2.06, 95% CI 1.06-4.02, P = .03), compared with the normal AT activity level (≥ 70%). ROC curve analysis showed that the prediction accuracy of AT was an area under the curve (AUC) of 0.66 (cutoff 58%, sensitivity 61.4%, specificity 68.2%, P = .0003). AT activity was significantly prognostic in the group with 20% to 50% predicted mortality (AUC 0.74, sensitivity: 24.0%-55.5%, specificity: 83.3%-93.0%). An early decrease in AT activity level in ICU patients may be a predictor of mortality at discharge.

Risk factors for mechanical ventilation and ECMO in COVID-19 patients admitted to the ICU: A multicenter retrospective observational study

BACKGROUND

The primary purpose of this study was to investigate risk factors associated with the need for mechanical ventilation (MV) and extracorporeal membrane oxygenation (ECMO) in COVID-19 patients admitted to the intensive care unit (ICU).

METHODS

We retrospectively enrolled 66 consecutive COVID-19 patients admitted to the ICUs of three Japanese institutions from February 2020 to January 2021. We performed logistic regression analyses to identify risk factors associated with subsequent MV and ECMO requirements. Further, multivariate analyses were performed following adjustment for Acute Physiology and Chronic Health Evaluation (APACHE) II scores.

RESULTS

At ICU admission, the risk factors for subsequent MV identified were: higher age (Odds Ratio (OR) 1.04, 95% Confidence Interval (CI) 1.00-1.08, P = 0.03), higher values of APACHE II score (OR 1.20, 95% CI 1.08-1.33, P < 0.001), Sequential Organ Failure Assessment score (OR 1.53, 95% CI 1.18-1.97, P < 0.001), lactate dehydrogenase (LDH) (OR 1.01, 95% CI 1.00-1.02, p<0.001) and C-reactive protein (OR 1.09, 95% CI 1.00-1.19, P = 0.04), and lower values of lymphocytes (OR 1.00, 95% CI 1.00-1.00, P = 0.02) and antithrombin (OR 0.95, 95% CI 0.91-0.95, P < 0.01). Patients who subsequently required ECMO showed lower values of estimated glomerular filtration rate (OR 0.98, 95% CI 0.96-1.00, P = 0.04) and antithrombin (OR 0.94, 95% CI 0.88-1.00, P = 0.03) at ICU admission. Multivariate analysis showed that higher body mass index (OR 1.19, 95% CI 1.00-1.40, P = 0.04) and higher levels of LDH (OR 1.01, 95% CI 1.01-1.02, P < 0.01) were independent risk factors for the need for MV. Lower level of antithrombin (OR 0.94, 95% CI 0.88-1.00, P = 0.03) was a risk factor for the need for ECMO.

CONCLUSION

We showed that low antithrombin level at ICU admission might be a risk factor for subsequent ECMO requirements, in addition to other previously reported factors.

Inherited antithrombin deficiency caused by a mutation in the SERPINC1 gene: A case report

RATIONALE

Inherited antithrombin deficiency (ATD) is a major cause of thrombotic deficiency. Genetic testing is of great value in the diagnosis of hereditary thrombophilia. Herein, we report a case of inherited ATD admitted to our hospital. We include the results of genealogy and discuss the significance of genetic testing in high-risk groups of hereditary thrombophilia.

PATIENT CONCERNS

A 16-year-old male patient presented with chest tightness, shortness of breath, wheezing, and intermittent fever (up to 39 °C) after strenuous exercise for 2 weeks. He also had a cough with white sputum with a small amount of bright red blood in the sputum and occasional back pain.

DIAGNOSES

The blood tests showed that the patient's antithrombin III concentration and activity were both significantly reduced to 41% and 43.2%, respectively. Enhanced chest computed tomography scans showed pulmonary infarction in the lower lobe of the right lung with multiple embolisms in the bilateral pulmonary arteries and branches. Lower vein angiography revealed a contrast-filling defect of the inferior vena cava and left common iliac vein. Thrombosis was considered as a differential diagnosis. His father and his uncle also had a history of thrombosis. The patient was diagnosed with inherited ATD. Further, peripheral venous blood samples of the family members were collected for whole-exome gene sequencing, and Sanger sequencing was used to verify the gene mutation site in the family. The patient and his father had a SERPINC1 gene duplication mutation: c.1315_1345dupCCTTTCCTGGTTTTTAAGAGAAGTTCCTC (NM000488.4).

INTERVENTIONS

An inferior vena cava filter was inserted to avoid thrombus shedding from the lower limbs. Urokinase was injected intermittently through the femoral vein cannula for thrombolysis. Heparin combined with warfarin anticoagulant therapy was sequentially administered. After reaching the international normalized ratio, heparin was discontinued, and oral warfarin anticoagulant therapy was continued. After discharge, the patient was switched to rivaroxaban as oral anticoagulation therapy.

OUTCOMES

The patient's clinical symptoms disappeared. reexamination showed that the thrombotic load was less than before, and the inferior vena cava filter was then removed.

LESSONS

By this report we highlight that gene detection and phenotypic analysis are important means to study inherited ATD.

Microsurgical Breast Reconstruction in Patients with Disorders of Hemostasis: Perioperative Risks and Management

BACKGROUND

Surgical and technological advances have resulted in the widespread adoption of microsurgical breast reconstruction. Many comorbidities that potentially might impair vasculature and wound healing are no longer considered contraindications for these procedures. However, some uncertainty still prevails regarding the perioperative management of patients with disorders of hemostasis.

METHODS

The authors combined a literature review with a retrospective chart review of patients with disorders of hemostasis who had undergone microsurgical breast reconstruction at the senior author's (J.F.) center between 2015 to 2020. Several disorders associated with thrombotic and/or hemorrhagic complications were identified, and a standardized risk assessment and management strategy was developed in cooperation with a hematologist.

RESULTS

Overall, 10 studies were identified comprising 29 patients who had a defined disorder of hemostasis and underwent microsurgical breast reconstruction. Seventeen microsurgical breast reconstructions were performed on 11 patients at the senior author's (J.F.) center. High factor VIII levels, heterozygous factor V Leiden, and heterozygous prothrombin mutation G20210A were the most common genetic or mixed genetic/acquired thrombophilic conditions. As expected, hereditary antithrombin, protein C, or protein S deficiencies were rare. Among hemorrhagic disorders, thrombocytopenia, platelet dysfunction, and von Willebrand disease or low von Willebrand factor levels were those factors most frequently associated with increased perioperative bleeding.

CONCLUSIONS

Patients should be screened for elevated risk of thrombosis or bleeding before undergoing microsurgical breast reconstruction, and positive screening should prompt a complete hematologic evaluation. Interdisciplinary management of these disorders with a hematologist is essential to minimize risks and to obtain optimal reconstructive results.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Risk, IV.

Coagulation parameters predict COVID-19-related thrombosis in a neural network with a positive predictive value of 98%

Thrombosis is a major clinical complication of COVID-19 infection. COVID-19 patients show changes in coagulation factors that indicate an important role for the coagulation system in the pathogenesis of COVID-19. However, the multifactorial nature of thrombosis complicates the prediction of thrombotic events based on a single hemostatic variable. We developed and validated a neural net for the prediction of COVID-19-related thrombosis. The neural net was developed based on the hemostatic and general (laboratory) variables of 149 confirmed COVID-19 patients from two cohorts: at the time of hospital admission (cohort 1 including 133 patients) and at ICU admission (cohort 2 including 16 patients). Twenty-six patients suffered from thrombosis during their hospital stay: 19 patients in cohort 1 and 7 patients in cohort 2. The neural net predicts COVID-19 related thrombosis based on C-reactive protein (relative importance 14%), sex (10%), thrombin generation (TG) time-to-tail (10%), α₂-Macroglobulin (9%), TG curve width (9%), thrombin-α₂-Macroglobulin complexes (9%), plasmin generation lag time (8%), serum IgM (8%), TG lag time (7%), TG time-to-peak (7%), thrombin-antithrombin complexes (5%), and age (5%). This neural net can predict COVID-19-thrombosis at the time of hospital admission with a positive predictive value of 98%-100%.

Idarucizumab in Dabigatran-Treated Patients with Acute Ischemic Stroke Receiving Thrombolytic Therapy

Background and Objectives: Thrombolytic therapy with recombinant tissue-type plasminogen activator (rt-PA) is used to treat acute ischemic stroke. Dabigatran is a reversible thrombin inhibitor approved for stroke prevention in patients with nonvalvular atrial fibrillation. In such cases, thrombolytic therapy can be administered to certain patients after idarucizumab treatment. We evaluated the effectiveness of idarucizumab in dabigatran-treated patients receiving rt-PA. Materials and Methods: We included the data of nine idarucizumab-treated patients from the Riga East University Hospital Stroke Registry from 2018 to 2022 in our retrospective medical records analysis. We used the National Institutes of Health Stroke Scale (LV-NIHSS) score and modified Rankin scale (mRS) on admission and discharge to evaluate neurological deficit and functional outcomes. Results: We analyzed the data of nine patients (seven males and two females) with a mean age of 75.67 ± 8.59 years. The median door-to-needle time for all patients, including those who received idarucizumab before rt-PA, was 51 min (IQR = 43–133); the median LV-NIHSS score was 9 (IQR = 6.0–16.0) on admission and 4 (IQR = 2.5–4.0) at discharge; and the intrahospital mortality rate was 11.1% due to intracranial hemorrhage as a complication of rt-PA. Conclusions: Our study shows that idarucizumab as an antidote of dabigatran appears to be effective and safe in patients with acute ischemic stroke. Furthermore, the administration of idarucizumab slightly prolongs the door-to-needle time; however, the majority of cases showed clinical improvement after receiving therapy. Further randomized controlled trials should be performed to evaluate the safety and effectiveness of idarucizumab for acute ischemic stroke treatment.

Low antithrombin levels are associated with low risk of cardiovascular death but are a risk factor for cancer mortality

Background

Thrombosis is common in subjects suffering from cardiovascular diseases (CVD) and cancer. Hypercoagulation plays a pivotal role in the pathophysiology of thrombosis. Therefore, the inactivation of thrombin, the key enzyme in coagulation, is tightly regulated via antithrombin (AT). AT deficiency is related to thrombosis and cardiovascular death. In this study we investigated the association between AT levels and mortality, in particularly cardiovascular-related and cancer-related death in the general population.

Methods

We studied the association of AT levels and mortality in a prospective cohort sampled from the general Italian population (n = 19,676). AT levels were measured in the baseline samples, and mortality was recorded during a median follow-up period of 8.2 years. Cox regression was performed to investigate the association of all-cause, CVD-related and cancer-related mortality with variations in AT levels.

Results

In total, 989 subjects died during follow-up, of which 373 subjects of CVD and 353 of cancer-related causes. Cox analysis revealed that, after adjustment for age, sex, current smoking, BMI, diabetes, hypertension, hypercholesterolemia, history of cardiovascular disease, history of cancer, vitamin K antagonists, antiplatelet medication, heparin and oral contraceptives AT levels were not associated with all-cause mortality (HRQ1vsQ5: 0.92, 95% CI:0.74–1.15). Interestingly, the risk of CVD-related mortality was reduced in subjects with low AT levels compared to subjects with higher AT levels, after adjustment for age and sex and other confounders did not change the association (HRQ1vsQ5: 0.64, 95% CI:0.44–0.91). Moreover, low AT levels were associated with increased cancer mortality in a fully adjusted model (HRQ1vsQ2-5: 1.26, 95% CI:0.88–1.81).

Conclusions

Low AT levels are associated to a lower risk of fatal cardiovascular events in the general population, regardless of age, sex and medication use. In contrast, low AT levels are associated with lower cancer survival. For the first time we show that AT levels lower than the normal range in the general population, even before the development or diagnosis of cancer, are associated with an elevated risk of cancer death.

Ischemic stroke with cancer: Hematologic and embolic biomarkers and clinical outcomes

BACKGROUND

Patients with cancer and acute ischemic stroke (AIS) face high rates of recurrent thromboembolism or death.

OBJECTIVES

To examine whether hematologic and embolic biomarkers soon after AIS are associated with subsequent adverse clinical outcomes.

METHODS

We prospectively enrolled 50 adults with active solid tumor cancer and AIS at two hospitals from 2016 to 2020. Blood was collected 72-120 h after stroke onset. A 30-min transcranial Doppler (TCD) microemboli detection study was performed. The exposure variables were hematologic markers of coagulation (D-dimer, thrombin-antithrombin), platelet (P-selectin), and endothelial activation (thrombomodulin, soluble intercellular adhesion molecule-1 [sICAM-1], soluble vascular cell adhesion molecule-1 [sVCAM-1]), and the presence of TCD microemboli. The primary outcome was a composite of recurrent arterial/venous thromboembolism or death. We used Cox regression to evaluate associations between biomarkers and subsequent outcomes.

RESULTS

During an estimated median follow-up time of 48 days (IQR, 18-312), 43 (86%) participants developed recurrent thromboembolism or death, including 28 (56%) with recurrent thromboembolism, of which 13 were recurrent AIS (26%). In unadjusted analysis, D-dimer (HR 1.6; 95% CI 1.2-2.0), P-selectin (HR 1.9; 95% CI 1.4-2.7), sICAM-1 (HR 2.2; 95% CI 1.6-3.1), sVCAM-1 (HR 1.6; 95% CI 1.2-2.1), and microemboli (HR 2.2; 95% CI 1.1-4.5) were associated with the primary outcome, whereas thrombin-antithrombin and thrombomodulin were not. D-dimer was the only marker associated with recurrent AIS (HR 1.2; 95% CI 1.0-1.5). Results were generally consistent in analyses adjusted for important prognostic variables.

CONCLUSIONS

Markers of hypercoagulability and embolic disease may be associated with adverse clinical outcomes in cancer-related stroke.

The Heparin-Antithrombin Product: A Novel Value for Pediatric Extracorporeal Anticoagulation

Hematologic complications are a source of morbidity and mortality for patients receiving extracorporeal membrane oxygenation (ECMO) support. There is no consensus strategy for monitoring anticoagulation for children supported with ECMO. This study evaluated a novel measurement of anticoagulation for children on ECMO. This was a single-center observational study of children supported with ECMO from 2015 to 2020. Each patient's current unfractionated heparin dose was multiplied by the current antithrombin III (AT) level to obtain a novel anticoagulation value, the heparin-antithrombin product (HAP). This value was compared with the heparin dose, AT, and activated clotting time (ACT) to predict anti-Xa value using linear correlation and decision tree methods. Data were obtained from 128 patients supported with ECMO. The HAP value was more highly correlated with anti-Xa level than heparin dose, AT level, and ACT. This correlation was highest in the neonatal population (r = .7). The variable importance metrics from the regression tree and random forest models both identified the HAP value as the most influential predictor variable for anti-Xa value. The HAP value is more highly correlated with the anti-Xa level than heparin dose, AT level, or ACT. Further research is needed to evaluate the effectiveness of the HAP value as a measurement of anticoagulation for children on ECMO.

Correlation of Antithrombin Functional Status and Levels with Liver Fibrosis in Patients with Hepatitis C

BACKGROUND

Abnormal levels of coagulation factors and their inhibitors have shown association with liver diseases. The objective of this study was to determine the qualitative and quantitive status of antithrombin (AT) in patients with chronic liver disease associated hepatitis C infection and their correlation with severity of liver fibrosis.

METHODS

In this study, 75 (43 male and 32 female) known patients with chronic liver disease associated hepatitis C infection were enrolled. AT activity and quantitative immunoassays were carried out using Stachrom AT reagent kit (Diagnostica Stago, France) and Liatest AT reagent (Diagnostica Stago, France), respectively. Hepatic biopsies were obtained and graded for liver fibrosis from all study participants.

RESULTS

Of the 75 patients, 45 had normal AT while 30 showed lower activity of AT. Similarly, the quantitative assay showed reduced levels of AT in 30 patients and normal levels in 45 patients.

CONCLUSIONS

In the early stages of liver fibrosis, AT activity and antigenic levels were found to be normal or minimally affected. While advanced stages of the disease showed markedly reduced levels of AT and activity. Hence, it can be concluded that the degree of fibrosis affects the status of AT.

In vivo delivery of CRISPR-Cas9 using lipid nanoparticles enables antithrombin gene editing for sustainable hemophilia A and B therapy

Hemophilia is a hereditary disease that remains incurable. Although innovative treatments such as gene therapy or bispecific antibody therapy have been introduced, substantial unmet needs still exist with respect to achieving long-lasting therapeutic effects and treatment options for inhibitor patients. Antithrombin (AT), an endogenous negative regulator of thrombin generation, is a potent genome editing target for sustainable treatment of patients with hemophilia A and B. In this study, we developed and optimized lipid nanoparticles (LNPs) to deliver Cas9 mRNA along with single guide RNA that targeted AT in the mouse liver. The LNP-mediated CRISPR-Cas9 delivery resulted in the inhibition of AT that led to improvement in thrombin generation. Bleeding-associated phenotypes were recovered in both hemophilia A and B mice. No active off-targets, liver-induced toxicity, and substantial anti-Cas9 immune responses were detected, indicating that the LNP-mediated CRISPR-Cas9 delivery was a safe and efficient approach for hemophilia therapy.

Unraveling a borderline antithrombin deficiency case with quantitative mass spectrometry

Antithrombin deficiency diagnostics by first-line activity tests suffer from a lack of sensitivity sometimes resulting in diagnostic uncertainty. We here present a case of a woman with recurrent pregnancy loss who was screened for inherited thrombophilia. Antithrombin activity was borderline low, resulting in uncertainty about the correct diagnosis. Using a mass spectrometry-based test, the antithrombin protein of the patient was characterized at the molecular level and a heterozygous p.Pro73Leu mutation was identified. The mutation, also known as antithrombin "Basel," increases the risk of venous thromboembolism and obstetric complications. This case is illustrative of current antithrombin deficiency screening, in which diagnoses may be missed by traditional diagnostics. Next-generation protein diagnostics by mass spectrometry provides molecular insight into the proteoforms present in vivo. This information is essential for laboratory specialists and clinicians to unambiguously diagnose patients and will aid in evolving healthcare from traditional to precision diagnostics.

Pharmacokinetic modeling and simulation support for age- and weight-adjusted dosing of dabigatran etexilate in children with venous thromboembolism

BACKGROUND

Dabigatran etexilate (DE), a direct oral thrombin inhibitor, has been evaluated in children with venous thromboembolism (VTE) using oral solution, pellets, or capsules.

OBJECTIVES

This study evaluated DE pharmacokinetics (PK) in children with VTE and the appropriateness of a DE pediatric age- and weight-based dosing algorithm.

PATIENTS/METHODS

A population PK model was fitted to data from four single-arm and one randomized, comparative pediatric VTE studies (358 children aged birth to <18 years; 2748 PK observations) and one healthy-adult study (32 males aged <40 years; 1523 PK observations) using nonlinear mixed-effects modeling. A stepwise, covariate, model-building procedure evaluated the influence of covariates (e.g., age, body weight, body surface area [BSA]-normalized renal function, and sex). The final model was used to evaluate the pediatric dosing algorithm, with simulations comparing pediatric trough exposure with reference exposure defined for the pediatric studies.

RESULTS

The population PK of dabigatran was adequately described by a two-compartment model with first-order elimination and absorption. Age, weight, BSA-normalized renal function, and sex were statistically significant covariates (all P < .05). Apparent clearance increased with age (independently of body weight), diminished with decreasing BSA-normalized renal function, and was lower in females than males. All disposition parameters increased with body weight escalation (allometric scaling). Simulations confirmed that for all DE formulations, the final pediatric dosing algorithms achieved reference exposure without dose adjustment.

CONCLUSIONS

Using a population PK model of DE for children with VTE, simulations showed that the final dosing algorithms were appropriate for all DE formulations; no dose titration was needed.