Activated charcoal helps in the diagnosis of dabigatran overdose: A case study

The direct-acting oral anticoagulant dabigatran etexilate (DE) targets thrombin and is used widely to prevent thromboembolism. A 79-year-old man was admitted to the Emergency Department due to anuria for 2 days. An urgent laboratory examination revealed a serum creatinine concentration of 888 µmol/L. He was diagnosed with acute exacerbation of chronic renal insufficiency. During continuous renal replacement therapy (CRRT), the coagulation test showed a severe reduction in the fibrinogen level as well as a significantly prolonged prothrombin time (PT) and activated partial thromboplastin time (APTT). The patient had been taking DE (110 mg twice daily) for a long time and had not suspended the medication or reduced the dose during the worsening of anuria. Therefore, it should be evaluated before considering plasma replacement therapy for the patient, whether the abnormal coagulation parameters were induced by interference of excessive DE. Tentatively, we used activated charcoal to treat the plasma and then retested the fibrinogen, PT, and APTT. Results showed that the coagulation indices nearly returned to normal. The present case indicated that activated charcoal could adsorb DE in plasma effectively and eliminate its interference with coagulation test results, thereby providing support for clinical diagnosis and treatment.

Ramadan intermittent fasting is associated with improved anticoagulant activity among healthy people: a case-control study

Data on the pathophysiological mechanisms of hemostatic alterations in the thrombotic events that occur during Ramadan intermittent fasting (RIF), particularly in the natural coagulation inhibitors, are very limited. Thus, our objective was to evaluate the effect of RIF on the natural anticoagulants level, antithrombin, protein C, and total and free protein S (PS) in healthy participants. Participants were divided into two groups. Group I consisted of 29 healthy fasting participants whose blood samples were taken after 20 days of fasting. Group II included 40 healthy non-fasting participants whose blood samples were taken 2-4 weeks before the month of Ramadan. Coagulation screening tests including prothrombin time (PT), activated partial thromboplastin time (APTT) and plasma fibrinogen level, natural anticoagulants; antithrombin, protein C, free and total PS and C4 binding protein (C4BP) levels were evaluated in the two groups. High levels of total and free PS without change in antithrombin, protein C, and C4BP levels were noted in the fasting group as compared with non-fasting ones (p < 0.05). PT and APTT showed no difference between the two groups. However, the fibrinogen level was higher in the fasting group. In conclusion, RIF was found to be associated with improved anticoagulant activity in healthy participants, which may provide temporal physiological protection against the development of thrombosis in healthy fasting people.

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.