TFPI Levels Research Articles

The common VTE-protective G haplotype of F5 increases factor V-short, TFPI function, and risk of bleeding

AbstractThe G haplotype is a group of co-inherited single nucleotide variants in the F5 gene that reduce venous thromboembolism (VTE) risk. Although 7% of the population is homozygous for the G haplotype (F5-G/G), the underlying mechanism of VTE protection is poorly understood. Using RNA sequencing data from 4651 blood donors in the INTERVAL study, we detected a rare excision event at the factor V (FV)-short splice sites in 5% of F5-G/Gs carriers as compared with 2.16% of homozygotes for the F5 reference sequence (F5-ref; P = .003). Highly elevated (∼10-fold) FV-short, an FV isoform that lack most of the B-domain, has been linked with increased tissue factor inhibitor α (TFPIα) levels in rare hemorrhagic diathesis, including East Texas bleeding disorder. To ascertain whether the enhanced FV-short splicing seen in F5-G/G INTERVAL participants translated to increased plasma FV-short levels, we analyzed plasma samples from 7 F5-G/G and 13 F5-ref individuals in a recall-by-genotype study. A ∼2.2-fold higher amount of FV-short was found in a plasma pool from F5-G/G participants when compared with the pool of F5-refs (P = .029), but there was no difference in the total FV levels. Although no significant difference in TFPI levels were found, F5-G/Gs showed a ∼1.4-fold TFPI-dependent increase in lag time to thrombin generation than F5-refs (P = .0085). Finally, in an analysis of 117 699 UK Biobank participants, we discovered that, although being protective against VTE, the G haplotype also confers an increase in bleeding episodes (P = .011). Our study provides evidence that the effect of the common G haplotype is mediated by the FV-short/TFPI pathway.

Extracellular vesicle tissue factor and tissue factor pathway inhibitor are independent discriminators of sepsis-induced coagulopathy

BackgroundSepsis-induced disseminated intravascular coagulopathy (DIC) remains a challenging clinical entity associated with significant morbidity and mortality. Endothelial injury or activation and extracellular vesicles (EV) are postulated as important determinants of DIC. However, there is limited research available which specifically tests the discriminatory ability of these characteristics in sepsis-induced coagulopathy. MethodsIn this prospective, single-centre study we collected plasma samples within 24 hours after sepsis diagnosis and followed these patients for five consecutive days. Overt DIC was determined by the ISTH-DIC score. 87 sepsis patients were recruited (35 with overt DIC) and presented with increased levels of EV, EV-associated TF activity (TF-PCA), E-selectin, TF and TFPI at admission compared to healthy subjects. ResultsOnly TFPI levels and TF-PCA discriminated between sepsis patients with or without DIC (AUC 0.76, p = 0.0002). Increased TF-PCA was not sensitive in detecting sepsis-associated DIC, however levels above 1.38 pg/mL showed a high specificity in this cohort (sensitivity 27%, specificity 95%). The hazard ratio to progress to DIC over five days was 1.14 (95% CI 0.64 – 2.07) for TF-PCA levels of 0.5 pg/mL or higher and 3.18 (95% CI 1.74 – 5.79) for TFPI levels of 22.28 ng/mL or higher at admission. ConclusionThese findings highlight the critical balance between pro- and anticoagulant factors, especially the pivotal roles of TF-PCA and TFPI in an early phase of sepsis-induced DIC. Only EV-associated and functionally active TF and not TF antigen levels showed a predictive potential regarding DIC. These novel results might support the improvement of diagnostic or even therapeutic strategies to mitigate the devastating consequences of DIC in septic patients.

Exploration on the effect of anserine on the alleviation of DVT and its molecular mechanism

BackgroundThis study aimed to explore the regulatory effect of anserine on HUVEC cell injury and thrombosis in deep venous thrombosis (DVT) rats, and to elucidate the underlying molecular mechanisms.MethodsNon-targeted metabolomics data analyses were conducted using an ultra-performance liquid chromatography system Vanquish UHPLC and mass spectrometer to detect plasma metabolism profiles. The transcriptome sequencing and gene intervention experiments were performed to verify the regulatory effect. Further in vivo and in vitro experiments were performed. Enzyme-linked immunosorbent assay was used to detect the levels of P-selectin, E-selectin, and vWF, hematoxylin-eosin (HE) staining was performed to observe thrombotic and inflammatory cell infiltration, flow cytometry and TUNEL assays were performed to detect apoptosis, and qPCR and WB assays were conducted to determine the gene and protein expression.ResultsAnserine alleviated HUVECs injury, reduced adhesion molecule expression, and inflammation. It decreased P-selectin, E-selectin, vWF, THBD, TFPI levels, and apoptosis while promoting NOS3, ET-1, and NO release in HUVECs. In DVT rats, anserine reduced P-selectin, E-selectin, vWF, thrombosis, cell infiltration, apoptosis, and promoted NO release. Transcriptome sequencing and gene intervention confirmed anserine’s regulation of the PI3K-Akt pathway and coagulation via MYB. CARNMT1, a regulatory enzyme for anserine metabolism, increased anserine content, inhibiting coagulation, thrombosis, cell infiltration, and promoting NO release in rats.ConclusionThis study confirmed anserine could alleviate DVT by improving the inflammatory response, inhibiting blood agglutination, and promoting vasodilation, providing new potential therapeutic targets, important scientific evidence for the development of DVT management, and new clues for an in-depth understanding of its molecular mechanisms.

Abstract 3096: Role Of Circulating Phosphatidylserine In The Procoagulant Activity Of Amniotic Fluid

Background: Amniotic fluid (AF) embolism is one of the most catastrophic complications during pregnancy. While studies primarily attributed the procoagulability of AF to circulating tissue factor (TF), the exact mechanism remains unclear. Aims: Define the procoagulant mechanisms of AF. Methods: Clotting time assays were performed using normal human plasma or plasma depleted of factor (F)XII, XI, X, IX, VII, V, or prekallikrein (PK). Chromogenic substrate assays were used to quantify FX activation by the TF/FVIIa complex and prothrombin activation by FXa. Phosphatidylserine (PS) levels were quantified using a fluorometric kit. Results: AF shortened the clotting time of normal plasma from 572±83 to 160±2 seconds; AF-induced clotting times were equivalent for FXII, PK, FXI, FX, FIX, or FV-depleted plasma or in the presence of contact pathway inhibitors as compared to normal plasma. In contrast, the procoagulant effects of AF were diminished or absent for FVII-depleted plasma or in the presence of a blocking anti-TF antibody or low-molecular-weight heparin. In a purified system, AF reduced FX activation by the TF/FVIIa complex. The addition of a blocking anti-tissue factor pathway inhibitor (TFPI) antibody reversed the effect of AF on FX activation. Western blotting confirmed the existence of both TF and TFPI in AF. AF enhanced prothrombin activation by FXa. The addition of annexin V, or lactadherin, which bind to PS, or the use of Gla-domainless prothrombin mitigated the effect of AF on prothrombin activation. PS levels in AF and normal plasma were 811±376 and 10.4±3.8 μM, respectively. Conclusions: The procoagulability of AF is independent of the contact pathway while being sensitive to both TF and TFPI levels. Furthermore, PS in AF significantly contributes to its procoagulability. This knowledge is important when developing strategies to lessen the procoagulability of AF without compromising hemostasis in the setting of AF embolism-associated coagulopathy.

Efficacy and Safety of Concizumab Prophylaxis in Patients with Hemophilia A or B without Inhibitors: 56-Week Cut-Off Results of the Phase 3 explorer8 Study

Introduction Concizumab is an anti-tissue factor pathway inhibitor (TFPI) monoclonal antibody in development as a once-daily subcutaneous prophylactic treatment for hemophilia of all subtypes. Results from the 56-week cut-off of the prospective, multicenter, open-label explorer8 study (NCT04082429; phase 3) in patients with hemophilia A or B without inhibitors (HA/HB) are presented, further to the 32-week confirmatory analysis cut-off (CACO) results previously reported (Chowdary P et al. ISTH 2023, OC 59.1). Aim To assess the longer-term efficacy and safety of daily concizumab prophylaxis in patients with HA/HB. Methods Male patients (aged ≥12 years) with HA/HB were randomized 1:2 to no prophylaxis (arm 1; 24 weeks) or concizumab prophylaxis (arm 2; ≥32 weeks) or assigned to non-randomized concizumab prophylaxis (arms 3 and 4; ≥32 weeks). After the main part of the trial (24 weeks for arm 1), patients in arm 1 could switch to concizumab prophylaxis. After treatment restart following the treatment pause due to thromboembolic events, patients received a 1.0 mg/kg concizumab loading dose on Day 1, followed by an initial 0.20 mg/kg daily dose starting on Day 2, with potential adjustment to 0.15 or 0.25 mg/kg based on measured plasma concizumab concentration after week 4. Assessments at the 56-week cut-off included efficacy, safety, pharmacokinetic and pharmacodynamic measurements. Informed consent/ethics committee approval were obtained. Results The study included 148 patients (HA, n=82; HB, n=66), of which 21 patients were randomized to no prophylaxis (arm 1: HA, n=9; HB, n=12), 42 patients to concizumab prophylaxis (arm 2: HA, n=18; HB, n=24) and the remaining 85 patients were assigned to concizumab prophylaxis (non-randomized arms 3 and 4). After the main part of the trial, 17 patients from arm 1 switched to concizumab prophylaxis, receiving the same dosing regimen as patients in arms 2‒4 when first starting on concizumab. A total of 132 patients (HA, n=73; HB, n=59) completed the 56-week cut-off. The overall median (interquartile range) annualized bleeding rate (ABR) on concizumab prophylaxis in arms 1‒4 was 1.7 (0.0‒4.5) for HA and 2.8 (0.0‒6.4) for HB (Table 1); these results were also supported by the supportive secondary efficacy assessments. After treatment restart, no thromboembolic events were reported (Table 2). A total of 30 serious adverse events (AEs) were reported in 20 patients at the 56-week cut-off. As previously reported at CACO, one patient experienced a serious AE with fatal outcome (intra-abdominal hemorrhage) and 6 patients experienced AEs leading to withdrawal of concizumab treatment. The rate of injection site reactions was comparable to CACO. No hypersensitivity type reactions were reported in the study and low-titer anti-concizumab antibodies were detected in a total of 21 patients at the 56-week cut-off, with no apparent impact on bleeds or AEs. Concizumab plasma concentration remained stable over time. Free TFPI and thrombin peak levels continued to be stable over time. Conclusions Concizumab prophylaxis showed longer-term (≥1 year) efficacy in adult and adolescent patients with HA/HB at the 56-week cut-off, which was consistent with the results observed at CACO. Concizumab prophylaxis was considered safe and well tolerated in patients with HA/HB.

Persisting Endothelial Cell Activation and Hypercoagulability after Recovering from COVID-19: The Roadmap-Post COVID-19 Study

Background: In patients with severe COVID-19, activation of blood coagulation and endothelial cells orchestrated with complement activation and cytokine storm leads to disease worsening and death. Hypercoagulable state and endothelial cell activation and fibrinolytic unbalance are common alterations in patients with COVID-19 hospitalized either at the conventional medical ward or at the intensive care unit (ICU). Two systematic reviews highlight that D-dimer values are higher in non survivors as well as in patients with severe COVID-19 than in those with mild disease, showing the association between D-dimer levels and disease severity or death. Nevertheless, there are limited data in small series of patient, on the persistence of hypercoagulability and endothelial cell activation following recovery from COVID-19. Aims: To investigate the persistence of endothelial cell activation and hypercoagulability after recovery from COVID-19. Patients/Methods. COVID-19 survivors (n = 208) and 30 healthy individuals were enrolled in this study. Methods: In ,total, 208 COVID-19 survivors were included in the study; 125 males (60%) and 83 females (40%) with a median age of 50 years (IQR = 20, range 18 to 78 years). Biomarkers of hypercoagulability and endothelial cell activation: The procoagulant phospholipid-dependent clotting time (PPL-ct) was measured using a factor Xa-based clotting assay STA®-Procoag-PPL. Free-TFPI levels were measured with the ELISA Free TFPI, Asserachrom®; D-dimer and fibrin monomers (FM) were measured by STA Liatest D-Di and STA Liatest FM; soluble thrombomodulin (sTM) was measured by Asserachrom® TM. All assays were from Diagnostica Stago, Asnières, France. Heparanase-levels were measured with ELISA kits R&D. Systems (Lille France). Detection of anti-SARS-CoV2 antibodies: IgG and IgA anti-SARS-CoV-2 antibodies were detected in the sera of the survivors using a semi-quantitative commercial ELISA methodology (Euroimmun Medizinische Labordiagnostika AG, Lubeck, Germany) Results: The median interval between symptom onset and screening for SARS-CoV-2 antibodies was 62 days (IQR = 22 days). Antibodies against SARS-CoV-2 were detected in all survivors enrolled in the study. The median level of IgG and IgA antibodies was 5.68 U (IQR = 6.19) and 3.62 U (IQR = 5.36), respectively. In 112 survivors with known blood group, 48 (43%) were group O, 44 (39%) were group A, 14 (13%) were group B, and 6 (5.4%) were group AB. Survivors showed significantly higher levels of D-Dimers, FM, TFPI, and heparanase as compared to that of the control group. Survivors had significantly shorter PPL-ct . One out of four of COVID-19 survivors showed increase at least one biomarker of endothelial cell activation or hypercoagulability (Table1). Elevated D-dimer was associated with older age. Elevated FM was associated with female gender. Elevated heparanase was independently associated with male gender. Decreased Procoag-PPL clotting time was associated with female gender. Univariate and multivariate logistic regression analysis examining predictors of hypercoagulability in study cohort of COVID-19 survivors are reported in table 2 . The interval between COVID-19 diagnosis and assessment was not associated with the changes of the studied biomarkers. Conclusion: The ROADMAP-postCOVID-19 study offers an analysis of a large panel of biomarkers of endothelial cell activation and hypercoagulability in survivors of COVID-19. The study documents that two months after symptoms' onset, activation of endothelial cells, in vivo thrombin generation, and fibrin lysis are frequent phenomena up to two months from COVID-19 symptom onset. The data presented herein allow to propose that evaluation of blood hypercoagulability (using D-dimer for instance) and endothelial cell activation could offer the possibility of prompt identification of COVID-19 survivors at risk of post-COVID-19 vascular complications. The findings of the present study underline the need for a thorough evaluation of a potential correlation between the sustained hypercoagulability and endothelial cell activation with the symptomatology of long-COVID-19 to apply anticipated diagnostic and therapeutic strategies. The clinical relevance of the identified biomarkers of endothelial activation and hypercoagulability in the assessment of the risk of long COVID-19 must be investigated in a prospective study. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Endogenous Thrombin Generation Potential in Patients with Pulmonary Embolism and Its Relevance to Thrombo-Inflammatory Biomarkers

Background: Pulmonary embolism (PE) is a catastrophic outcome in patients with venous thrombosis and third leading cardiovascular cause of death after myocardial infraction and stroke, estimates around 100,000 deaths annually.Inflammation, hemostatic dysregulation including fibrinolytic imbalance, endothelial compromise, and generation of thrombotic mediators, along with cellular defects and hemodynamic derangement contribute to the pathogenesis of PE.Endogenous thrombin generation contributes to the overall pathology of PE. The purpose of this study is to investigate endogenous thrombin potential (ETP) and the circulating biomarkers of fibrinolytic, inflammatory, and endothelial dysfunction in PE samples. Methods: Citrated blood samples from 400 patients with confirmed PE were collected at Loyola University Medical Center and Gottlieb Memorial Hospital under an IRB approved protocol. Normal human plasma (NHP) comprised of 25 male and 25 female samples were obtained from a commercial source. Thrombin generation studies were carried out using a commercially available a kinetic system. Endogenous GAG's contents were measured by fluorogenic quenching method. Thrombin generation parameters such as peak thrombin, lag time and area under the curve (AUC) were compiled. Plasma samples were retrospectively analyzed for biomarkers, including D-Dimer, PAI-1, tPA, TAFIa, vWF, CRP, IL6, TFPI and VEGF using commercially available sandwich ELISA methods. Results were compiled as mean ± SD and analyzed for significance and correlation by using GraphPad Prism software. Result: On a cumulative basis, PE patients showed a wide variation in thrombin generation parameters (Table 1). Biomarker analysis showed elevated levels of D-Dimer (37.05-fold), CRP (35.34-folds), IL6 (21.62-folds), tPA (4.69-folds), PAI-1a (3.95-folds), VEGF (2.38-folds), TFPI (2.17-folds), GAG's (1.92-folds), vWF (1.89-folds), and TAFIa (1.21-folds). Peak thrombin levels exhibited varying degree of positive and negative correlations with various biomarkers as illustrated in figure 1. Thrombin levels showed significant negative correlations with tPA, endogenous GAG's & TFPI, while positively correlated with VEGF. D-dimer showed positive correlations with CRP & IL6. PAI-1 demonstrated positive correlations with tPA, IL6, and endogenous GAG's. tPA showed negative correlation with TAFI, while positive correlations with endogenous GAG's, and TFPI. vWF showed positive correlations CRP, IL6, and endogenous GAG's. CRP showed positive correlations with IL6. Endogenous GAG's showed positive correlations with TFPI while TFPI showed negative correlation with VEGF. Conclusion: PE patients exhibit a wide variation in endogenous thrombin generation parameters. Overall, peak thrombin and ETP were decreased, whereas the lag time was increased. The increase in thrombo-inflammatory markers is suggestive of upregulation of thrombogenesis, and inflammatory processes in these patients. Thus, the profiling of thrombo-inflammatory biomarkers along with thrombin generation profile may provide additional information on the pathogenesis and severity of PE. However, biomarkers of hemostatic activation, vascular dysfunction and inflammation were increased. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Persisting Endothelial Cell Activation and Hypercoagulability after COVID-19 Recovery—The Prospective Observational ROADMAP-Post COVID-19 Study

Background. Hypercoagulable state and endothelial cell activation are common alterations in patients with COVID-19. Nevertheless, the hypothesis of persistent hypercoagulability and endothelial cell activation following recovery from COVID-19 remains an unresolved issue. Objectives. To investigate the persistence of endothelial cell activation and hypercoagulability after recovery from COVID-19. Patients/Methods. COVID-19 survivors (n = 208) and 30 healthy individuals were enrolled in this study. The following biomarkers were measured: procoagulant phospholipid-dependent clotting time (PPL-ct), D-Dimer, fibrin monomers (FM), free Tissue factor pathway inhibitor (free-TFP)I, heparinase, and soluble thrombomodulin (sTM). Antibodies against SARS-CoV-2 (IgG and IgA) were also measured. Results. The median interval between symptom onset and screening for SARS-CoV-2 antibodies was 62 days (IQR = 22 days). Survivors showed significantly higher levels of D-Dimers, FM, TFPI, and heparanase as compared to that of the control group. Survivors had significantly shorter PPL-ct. Elevated D-dimer was associated with older age. Elevated FM was associated with female gender. Elevated heparanase was independently associated with male gender. Decreased Procoag-PPL clotting time was associated with female gender. One out of four of COVID-19 survivors showed increase at least one biomarker of endothelial cell activation or hypercoagulability. Conclusions. Two months after onset of COVID-19, a significant activation of endothelial cells and in vivo thrombin generation persists in at least one out of four survivors of COVID-19. The clinical relevance of these biomarkers in the diagnosis and follow-up of patients with long COVID-19 merits to be evaluated in a prospective clinical study.

Comprehensive Multi-Parameter Characterisation of Circulating Extracellular Vesicles from Rivaroxaban-Treated VTE Patients Reveals Reduced Inflammation and Ameliorated Endothelial Dysfunction

Venous Thromboembolism (VTE) remains a significant cause of morbidity and mortality worldwide. Rivaroxaban, a direct oral factor Xa inhibitor, mediates anti-inflammatory and cardiovascular-protective effects besides its well-established anticoagulant properties, however, these remain poorly characterized. Extracellular vesicles (EVs) are important circulating messengers regulating a myriad of biological and pathological processes and may be highly relevant to the pathophysiology of VTE as they reflect alterations in platelet and endothelial biology. However, the effects of Rivaroxaban on circulating pro-inflammatory EVs in VTE patients remain unknown. We hypothesized that rivaroxaban's anti-inflammatory properties are reflected upon differential molecular profiles of circulating EVs.Single-episode VTE patients anticoagulated with 20 mg Rivaroxaban or warfarin at a target INR of 2.0-3.0, respectively, who had commenced therapy no sooner than 3 months previously were recruited following informed written consent at the Mater Misericordiae University Hospital, Dublin, Ireland. Patient data including age, sex, BMI, prevalent risk factors and comorbidities were collected. Patients on warfarin therapy had a time in therapeutic range of at least 55% and an INR in target range at time of blood sampling. Exclusion criteria included known pro-inflammatory conditions, active malignancy, recurrent VTE, antiphospholipid syndrome, bleeding or platelet function disorders, use of anti-platelet drugs, and thrombocytopenia.To address the hypothesis, we firstly used a combination of Nanoparticle Tracking Analysis (NTA) and flow cytometry to comprehensively characterise differences in the concentration and size of small (0-200 nm) and large (200-1000 nm) circulating EVs, respectively. Statistical analysis revealed a trend towards reduced levels of circulating small and large EVs in Rivaroxaban-treated VTE patients compared with matched warfarin controls. Moreover, small and large EVs measured in the patients plasma correlated strongly and highly significantly (r=0.804, p<0.0001), indicating a concomitant decrease in both populations. As circulating EVs are considered pro-coagulant and pro-inflammatory, these results may point towards an ameliorated baseline pro-inflammatory state of VTE patients anticoagulated with Rivaroxaban. To further uncover Rivaroxaban-mediated alterations, we next compared proteomic profiles of circulating EVs. We robustly quantified over 300 vesicular proteins. Statistical analysis of the protein expression level using a student's t-test with a false discovery rate of 5% and a minimal fold change of 0.1 identified differential protein expression of a tightly regulated cluster of proteins involved in negative feedback regulation of inflammatory and coagulation pathways in Rivaroxaban-treated patients, which may in part contribute to the superior outcomes of Rivaroxaban-treated patients seen in recent clinical trials. Furthermore, we recently established that Rivaroxaban potentially ameliorates endothelial dysfunction in a cohort of non-valvular atrial fibrillation patients. Therefore, we aimed to also assess circulating markers of endothelial activation (Intercellular Adhesion Molecule 1 [ICAM-1] and Tissue Factor Pathway Inhibitor [TFPI]). Intriguingly, Rivaroxaban-treated patients exhibited an increase in plasma TFPI levels with a simultaneous decrease in soluble ICAM-1, potentially pointing towards ameliorated endothelial dysfunction in Rivaroxaban-treated VTE patients relative to warfarin.Collectively, we established that EV proteomic signatures are powerful biological sensors of Rivaroxaban's anti-inflammatory potential. Moreover, Rivaroxaban therapy may ameliorate endothelial dysfunction relative to warfarin. These findings are of translational relevance towards characterizing the anti-inflammatory and cardiovascular-protective mechanisms associated with Rivaroxaban therapy. DisclosuresKevane: Leo Pharma: Research Funding. Murphy: Bayer Pharma: Research Funding. Ni Ainle: Daiichi-Sankyo: Research Funding; Actelion: Research Funding; Leo Pharma: Research Funding; Bayer Pharma: Research Funding. Maguire: Bayer Pharma: Research Funding; Actelion: Research Funding.

Different Profiles of Cytokines, Chemokines and Coagulation Mediators Associated with Severity in Brazilian Patients Infected with Dengue Virus.

The incidence of dengue in Latin America has increased dramatically during the last decade. Understanding the pathogenic mechanisms in dengue is crucial for the identification of biomarkers for the triage of patients. We aimed to characterize the profile of cytokines (IFN-γ, TNF-α, IL-1β, IL-6, IL-18 and IL-10), chemokines (CXCL8/IL-8, CCL2/MCP-1 and CXCL10/IP-10) and coagulation mediators (Fibrinogen, D-dimer, Tissue factor-TF, Tissue factor pathway inhibitor-TFPI and Thrombomodulin) during the dengue-4 epidemic in Brazil. Laboratory-confirmed dengue cases had higher levels of TNF-α (p < 0.001), IL-6 (p = 0.005), IL-10 (p < 0.001), IL-18 (p = 0.001), CXCL8/IL-8 (p < 0.001), CCL2/MCP-1 (p < 0.001), CXCL10/IP-10 (p = 0.001), fibrinogen (p = 0.037), D-dimer (p = 0.01) and TFPI (p = 0.042) and lower levels of TF (p = 0.042) compared to healthy controls. A principal component analysis (PCA) distinguished between two profiles of mediators of inflammation and coagulation: protective (TNF-α, IL-1β and CXCL8/IL-8) and pathological (IL-6, TF and TFPI). Lastly, multivariate logistic regression analysis identified high aspartate aminotransferase-to-platelet ratio index (APRI) as independent risk factors associated with severity (adjusted OR: 1.33; 95% CI 1.03–1.71; p = 0.027), the area under the receiver operating characteristics curve (AUC) was 0.775 (95% CI 0.681–0.869) and an optimal cutoff value was 1.4 (sensitivity: 76%; specificity: 79%), so it could be a useful marker for the triage of patients attending primary care centers.

The contribution of TFPIα to the hemostatic response to injury in mice

BackgroundTissue factor pathway inhibitor (TFPI) is an essential regulator of coagulation, limiting thrombin generation and preventing thrombosis. In humans and mice, TFPIα is the sole isoform present in platelets. ObjectiveHere, we asked whether TFPIα, because of its release from platelets at sites of injury, has a unique role in limiting the hemostatic response. MethodsTFPIα‐mutant (TfpiΔα/Δα) mice were generated by introducing a stop codon in the C‐terminus. Platelet accumulation, platelet activation, and fibrin accumulation were measured following penetrating injuries in the jugular vein and cremaster muscle arterioles, and imaged by fluorescence and scanning electron microscopy. Time to bleeding cessation was recorded in the jugular vein studies. ResultsTfpiΔα/Δα mice were viable and fertile. Plasma TFPI levels were normal in the TfpiΔα/Δα mice, no TFPI protein or activity was present in their platelets and thrombin‐antithrombin complex levels were indistinguishable from Tfpi+/+ littermates. There was a small, but statistically significant reduction in the time to bleeding cessation following jugular vein puncture injury in the TfpiΔα/Δα mice, but no measurable changes in platelet or fibrin accumulation or in hemostatic plug architecture following injury of the micro‐ or macrovasculature. ConclusionLoss of TFPIα expression does not produce a global prothrombotic state in mice. Platelet TFPIα is expected to be released or displayed in a focal manner at the site of injury, potentially accumulating to high concentrations in the narrow gaps between platelets. If so, the data from the vascular injury models studied here indicate this is not essential for a normal hemostatic response in mice.

Venous thrombosis with oral postmenopausal hormone therapy: Roles of activated protein C resistance and tissue factor pathway inhibitor

BackgroundOral postmenopausal hormone therapy (HT) increases the risk of venous thrombosis (VT). We postulated that activated protein C (APC) resistance induced by HT is one of the mechanisms causing VT, and also assessed the role of one of the main determinants of APC resistance (i.e., tissue factor pathway inhibitor [TFPI]). MethodsWe performed a nested case‐control study embedded within two Women's Health Initiative hormone trials. Women were randomized to hormone therapy or placebo. Biomarkers were measured at baseline and after 1 year in 217 cases and 817 controls. ResultsIncreased APC resistance and decreased TFPI at baseline were associated with VT (odds ratio 1.20–2.06). However, women with such prothrombotic profile at baseline did not have further increased risk of VT when randomized to HT compared with placebo. Although there was no change in APC resistance or TFPI in placebo group after 1 year, HT group showed prothrombotic changes in the biomarkers (i.e., an increase in APC resistance) (mean [standard deviation] 0.39 [0.54]) and decrease in TFPI (−0.21 [0.50]: free TFPI, −0.24 [0.22]: TFPI activity −0.22 [0.20]: total TFPI). However, HT induced prothrombotic change in biomarkers did not increase risk of VT. ConclusionWomen with prothrombotic levels of APC resistance and TFPI at baseline were not at increased risk of VT when randomized to HT compared with placebo. This suggests that testing for these biomarkers before starting HT is not required. HT led to prothrombotic change in these biomarkers after one year, but this did not relate to increased risk of VT.

F5‐Atlanta: A novel mutation in F5 associated with enhanced East Texas splicing and FV‐short production

BackgroundElucidating the molecular pathogenesis underlying East Texas bleeding disorder (ET) led to the discovery of alternatively spliced F5 transcripts harboring large deletions within exon 13. These alternatively spliced transcripts produce a shortened form of coagulation factor V (FV) in which a large portion of its B‐domain is deleted. These FV isoforms bind tissue factor pathway inhibitor alpha (TFPIα) with high affinity, prolonging its circulatory half‐life and enhancing its anticoagulant effects. While two missense pathogenic variants highlighted this alternative splicing event, similar internally deleted FV proteins are found in healthy controls. ObjectiveWe identified a novel heterozygous 832 base pair deletion within F5 exon 13, termed F5‐Atlanta (F5‐ATL), in a patient with severe bleeding. Our objective is to investigate the effect of this deletion on F5 and FV expression. Methods & ResultsAssessment of patient plasma revealed markedly elevated levels of total and free TFPI and a FV isoform similar in size to the FV‐short described in ET. Sequencing analyses of cDNA revealed the presence of a transcript alternatively spliced using the ET splice sites, thereby removing the F5‐ATL deletion. This alternative splicing pattern was recapitulated by heterologous expression in mammalian cells. ConclusionsThese findings support a mechanistic model consisting of cis‐acting regulatory sequences encoded within F5 exon 13 that control alternative splicing at the ET splice sites and thereby regulate circulating FV‐short and TFPIα levels.

Factor V Atlanta: A Novel Mutation in the F5 Gene Reveals Potential New Cis-Acting Elements Involved in Regulating FV-Short and TFPI Levels

Coagulation factor V (FV) is procofactor essential to normal hemostasis. Recently, a point mutation in exon 13 of the F5 gene (FV-East Texas; FV-ET), which encodes the B-domain, has been shown to result in an inherited moderate bleeding diathesis termed East Texas Bleeding Disorder. The mutation (F5 c. A2350G, according to the latest annotated reference sequence for the F5 transcript, NM_000130.4, originally reported as A2440G) greatly enhances alternative splicing at an otherwise weak splice site, which leads to the production of a new FV isoform, FV-short. FV-short, via an exposed acidic region, binds with high affinity to tissue factor pathway inhibitor alpha (TFPIα) and is thought to stabilize the inhibitor in blood thereby increasing its concentration via changes in clearance mechanisms. High levels of TFPIα as well as other regulatory mechanisms contribute to inhibition of thrombin generation leading to a clinical bleeding phenotype. Another family with a different point mutation (FV-Amsterdam, F5 c.C2588G) downstream from FV-ET was recently identified and found to have similar clinical and laboratory characteristics. A 43 year-old male with a history of recurrent intramuscular hematomas underwent laboratory investigation to identify the etiology of his bleeding tendency. Laboratory testing revealed a prolonged PT and aPTT that failed to correct after 50:50 mixing with normal human plasma (NHP) and normal activity levels of factors II, V, VII, VIII, IX, X, XI, XII, and XIII. A lupus anticoagulant was not detected. A thrombin generation assay revealed a prolonged lag time versus control plasma (20 min vs. 6 min). These findings were similar to FV-ET, and further studies revealed that the concentration of total TFPI and TFPIα were elevated in the patient. Surprisingly however, the levels of TFPI were much higher compared to those measured in FV-ET. Relative to NHP, total TFPI and TFPIα were increased 11-and 22-fold, respectively for the patient compared to 4- and 5-fold for FV-ET (Table 1). Remarkably, a point mutation in exon 13 was not identified. Rather, analysis performed on genomic DNA identified a heterozygous 832 base pair (bp) deletion within exon 13 (c.2413-3244del). This deletion is predicted to result in the omission of 277 amino acids preceding a frameshift and translation of 12 non-native amino acids followed by a stop codon.While this alteration should result in a functionally null allele, causing the patient to have 50% FV levels, the clinical and biochemical findings do not align with this genomic data. Western blotting of the patient's plasma using anti-FV heavy or light chain antibodies revealed the presence of full length (FL)-FV (330 kDa) protein as well as a strong band at 250 kDa representing FV-short. Using recombinant FV-short as a control, quantitative western blotting revealed the patient has very high levels of FV-short (50 nM) compared to FV-ET plasma (5-7 nM; Table 1). To reconcile these data with the genetic information, we performed RT-PCR analysis of blood cell RNA. Several different FV transcripts were identified including a putative FL-FV transcript, a transcript containing the 832 bp frameshift deletion, and a FV-short transcript identical to that from FV-ET. The latter finding was unexpected as the 832 bp deletion is located 3' to the FV-ET donor splice site. We hypothesize that encoded within this novel 832 bp deletion is a sequence that functions as a cis-acting element which regulates FV-short production under normal physiologic conditions. FV-short is constituently expressed to a minor degree in unaffected individuals (~0.2-0.4 nM). Removal of this 832 bp sequence through genetic deletion is predicted to facilitate upregulation of FV-short biosynthesis via enhanced splicing at the FV-ET donor/acceptor splice sites. The identification of the FV-Atlanta deletion and the FV-ET and FV-Amsterdam point mutations highlight a complicated mechanism by which FV-short levels are modulated by alternative splicing. Since FV-short has a major influence on TFPIα levels, these collective findings are clinically relevant and may represent an additional level of regulation existing in the initiation and propagation of coagulation. [Display omitted] DisclosuresZimowski:National Hemophilia Foundation/Shire: Other: Clinical Fellowship Award Recipient. Denning:Expression Therapeutics: Employment. Jhita:Expression Therapeutics: Employment. Rivera:Expression Therapeutics: Employment. Escobar:Bayer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Shire: Honoraria, Membership on an entity's Board of Directors or advisory committees; CSL Behring: Honoraria, Membership on an entity's Board of Directors or advisory committees; Genentech: Honoraria, Membership on an entity's Board of Directors or advisory committees; NovoNordisk: Honoraria, Membership on an entity's Board of Directors or advisory committees. Kempton:Genentech: Membership on an entity's Board of Directors or advisory committees. Camire:Bayer: Consultancy, Research Funding; Pfizer: Consultancy, Patents & Royalties, Research Funding; Novo Nordisk: Research Funding; Spark Therapeutics: Membership on an entity's Board of Directors or advisory committees.

Biomarkers of Thrombo-Inflammatory Responses in Pulmonary Embolism Patients With Pre-Existing Versus New-Onset Atrial Fibrillation.

Pulmonary embolism (PE) patients have an increased prevalence and incidence of atrial fibrillation (AF). Because comorbid AF increases risk of morbidity and mortality, we sought to investigate the role of thrombo-inflammatory biomarkers in risk stratifying patients who experience an acute PE episode. Study participants were enrolled from a Pulmonary Embolism Response Team (PERT) registry between March 2016 and March 2019 at Loyola University Medical Center and Gottlieb Memorial Hospital. This cohort was divided into 3 groups: PE patients with a prior diagnosis of AF (n = 8), PE patients with a subsequent diagnosis of AF (n = 11), and PE patients who do not develop AF (n = 71). D-dimer, CRP, PAI-1, TAFIa, FXIIIa, A2A, MP, and TFPI were profiled using the ELISA method. All biomarkers were significantly different between controls and PE patients (P < 0.05). Furthermore, TFPI was significantly elevated in PE patients who subsequently developed AF compared to PE patients who did not develop AF (157.7 ± 19.0 ng/mL vs. 129.0 ± 9.3 ng/mL, P = 0.0386). This study suggests that thrombo-inflammatory biomarkers may be helpful in indicating an acute PE episode. Also, elevated TFPI levels may be associated with an increased risk of developing AF after a PE.

Differences in the Coagulation Profile in Women with Mild and Severe Preeclampsia

Introduction:Different coagulations abnormalities have been referred in women with early oncet preeclampsia (EOP), but there are only few studies comparing those changes regarding to the severity of the disease. Aim:In this study we aimed to investigate the differences between the coagulation profile in women with mild and severe preeclampsia. Methods:This is an observational retrospective case-control study. Plasma samples were collected from 84 women divided into three groups, the healthy pregnant (HP) group (n=35), the mild preeclampsia (MP) group (n=34) and the severe preeclampsia (SP) group (n=15). The study population general characteristics are shown in Table 1. We studied the following biomarkers of hypercoagulability and endothelial cell activation: Tissue factor activity (TFa), Procoagulant phospholipid activity (PPL), Protein S, D-Dimers, Antithrombin, thrombomodulin, TFPI levels. All women were assessed with classic coagulation tests (aPTT and PT) fibrinogen levels and hemogram. Statistical analysis was performed using the PASW Statistics 17.0.2 (SPSS Inc.) for Windows. Results:Women with preeclampsia - mild or severe- showed significant increase of TFPI, TFa and TMa levels as compared to healthy pregnant women. No significant difference of TFPI, TFa was observed between MP and SP groups. In contrast, TMa levels were significantly increased in SP as compared to MP group. The ratio TFa/TFPI was also lower in SP as compared to MP-group. Women in MP or SP group had similarly shorter PPL clotting time as compared to HP group. D-dimer levels were increased in women with preeclampsia as compared to the HP group. D-Dimer levels were significantly higher in SP as compared to MP group. The levels of free PS activity in HP as well as MP and SP groups were lower than normal range in non-pregnant women and the value in MP was significantly lower than that of the HP or SP. Fibrinogen levels were not significantly different in the three studied groups of pregnant women. Prothrombin time was found to be increased in cases as compared to that in the controls. The mean value of prothrombin time in mild preeclampsia was 13.24±0.80 seconds and in severe preeclampsia it was seconds 14.77±0.96 and in pregnant controls 12.23±0.59 seconds (p&amp;lt;0.05 and p&amp;lt;0.001 respectively). The mean prothrombin time was found to increase with increasing severity of disease (p&amp;lt;0.001). The mean activated partial thromboplastin time were increased in mild preeclampsia and was 32.64±1.83 seconds and in severe preeclampsia it was 35.59±1.53 seconds and in pregnant controls 29.53±1.62 seconds (p&amp;lt;0.001). The activated partial thromboplastin time was found to increase with increasing severity of disease (p&amp;lt;0.001). The antithrombin III decreased in severe SP and MP or compared to pregnant controls (76.33±4.32 and 88.06±9.68 versus 95.40±0.36 respectively; p&amp;lt;0.001). This decrease is more pronounced in SP compared to MP (p&amp;lt;0.001). Conclusions:Preeclampsia is associated with endothelial cell activation as documented by the increase of TFa, soluble TM levels and TFPI levels in plasma. Release of soluble thrombomoduline and TFPI rather than TFa by endothelial cells appear to be related with degree of preeclampsia severity. Women with preeclampsia showed marked decrease of PPL clotting time indicating enhanced platelet activation that was independent of the severity of preeclampsia. In contrast, women with severe preeclampsia showed signs of enhanced hypercoagulability documented by the increase of D-dimer levels consumption of natural coagulation inhibitors and particularly of AT. This phenomenon tended to be reflected on the prolongation of PT and aPTT in women with severe preeclampsia. Disclosures No relevant conflicts of interest to declare.

Profile of Thrombin Generation Assay and Thromboelastometry in Women with Moderate and Severe Preeclampsia. the Roadmap-Preeclampsia Study

Introduction: Preeclampsia is a frequent vascular complication of pregnancy and figures among the major causes of maternal and neonatal morbidity and mortality. Early diagnosis and prompt, targeted treatment remain a unmet need. Hypercoagulability and endothelial cell activation are among the principal pathogenetic mechanisms in patients with preeclempsia. Development of diagnostic algorithms including clinically relevant biomarkers of hypercoagulability is expect to improve the management of preeclampsia. Among the numerous coagulation test, Global Coagulation Assays (GCA) such as thrombogram and thromboelastometry, could be of potential value for the evaluation of blood hypercoagulability. They provide information, on thrombin generation process, clot formation kinetics, clot firmness and even fibrinolysis potential. Aim: In this study we investigated the clinical accuracy of whole blood thromboelastometry (ROTEM®), and thrombin generation assay (calibrated automated thrombography: CAT® assay) to identify women with preeclampsia and we tried to compare their sensitivity. Methods: An observational retrospective case-control study was conducted. Plasma samples were collected from 84 women divided into three groups, the healthy pregnant (HP) group (n=35), the mild preeclampsia (MP) group (n=34) and the severe preeclampsia (SP) group (n=15). Thromboelastometry in whole blood was performed on ROTEM delta instrument (Tem Innovations GmbH, Werfen, Munich, Germany) with INTEM reagent. Thrombin generation triggered by PPP reagent low® (1 pM TF and 4µM phospholipid) was measured in platelet poor plasma. Thrombogram was also assessed in the presence or absence of thrombomodulin and the corresponding ration was calculated. Blood was collected at the diagnosis of preeclampsia (groups MP and SP) or at the equivalent months of pregnancy in the control group (HP). Statistical analysis was performed using the PASW Statistics 17.0.2 (SPSS Inc.) for Windows. Results: Thromboelastometry analysis showed that the clotting time (CT) was significantly longer in SP group as compared to MP and HP group. Both preeclampsia groups had longer clot formation time (CFT as compared to HP-group. MP-group had longer CFT as compared to SP-group. The α angle was significantly lower in SP-group as compared to the HP and MP groups. The maximum clot firmness was significantly higher in MP groups as compared to either HP or SP-group. The mean lysis (ML) was lower in both preeclampsia groups as compared to the HP group (Table 1). Thrombogram analysis showed that the lag-time of thrombin generation was significantly longer in both MP and SP groups as compared to HP group. Moreover, SP group showed significantly longer lag -time as compared to MP-group. Peak and the endogenous thrombin potential (ETP) were significantly higher in MP group as compared to either HP or SP groups. The mean rate index of the propagation phase of thrombin generation was not significantly different among the three groups whereas the thrombomodulin ratio for the ETP was significantly shorter in the SP-group (Table 2). Both tests showed a significant prolongation of the initiation phase of blood coagulation (reflected on CT and lag-time) in SP. The levels of clotting factors and fibrinogen were normal in all patients and none was on anticoagulant treatment. Thus, this prolongation reflects changes at the levels of TFPI and Thrmbomodulin reflecting an endothelial cell activation. ROTEM showed a decrease of the α-angle and MCF in SP group which is related with a lower platelet count in these patients. ROTEM showed enhanced fibrinolysis in both MP and SP groups Women with MP showed higher Peak and ETP than SP, MP showed higher ratio of ETP (TM+/TM-) than SP. Conclusion: The two GCA proved complementary information on the status of blood coagulation in pregnant women with preeclampsia. ROTEM provides information on clot formation kinetics and clot firmness as well as on fibrinolysis activation, which allow to differentiate SP from HP. However, the capacity of the assay for identification of patients with MP is limited. Thrombin generation assay showed a distinct profile between the three groups, which allowed differentiating the MP from HP as well as from SP. Disclosures No relevant conflicts of interest to declare.

Biomarkers of Hypercoagulability and Endothelial Cell Activation in Patients with Severe COVID-19 Admitted at the Intensive Care Unit. the Roadmap-COVID-19 Prospective Observational Study

Introduction: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease 2019 (COVID-19) characterized by acute pneumonia which may progress to respiratory failure and life-threatening complications, including acute respiratory distress syndrome (ARDS) and multisystem organ failure with fatal outcome. COVID-19 should be regarded as a systemic disease involving multiple systems. COVID-19 is associated with excessive inflammation, platelet activation, endothelial dysfunction, blood coagulation activation and fibrin formation. The development of a screening algorithm for the evaluation of endothelial and blood coagulation activation is an urgent need for the optimisation of the management of the patients with severe COVID-19. To this aim biomarkers of endothelial cell activation and hypercoagulability have central placeAim: The prospective observational monocentric cohort study ROADMAP-COVID-19 study aimed to evaluate the biomarkers of hypercoagulability and endothelial cell activation which they could be used in the development of a screening algorithm in patients with COVID-19Methods: The ROADMAP-COVID-19 study enrolled 90 consecutive patients hospitalized at Tenon University Hospital (AP-HP, Paris) between March 18th and April 30th, 2020 with confirmed SARS-CoV-2 infection admitted to the ICU with clinically deteriorated severe COVID-19 (ICU- group). Patients were assessed upon the first day to the ICU admission. The control group consisted 30 healthy individuals (C-group). All patients and controls were evaluated for, clotting times (PT and aPTT), fibrinogen, D-Dimers, antithrombin (AT), protein C (PC) and protein S (Ps) activity, clotting factors V (FV), VIII (FVIII) and XII (FXII), high molecular weight kininogen (HK), von Willebrand factor (FvW), thrombin generation assay (TG) using TF 20 pM-PPP-Reagent® (Thrombogram-Thrombinoscope from Stago), fibrin monomers (FM), free TFPI and TF activity, thrombomodulin activity (TM), TF expressing microparticles (the ratio TF/TFPI was also calculated) and Heparanase. The IL-6 levels were also measured. All patients hospitalized in conventional medical department or in ICU routinely received thromboprophylaxis with body weight adapted enoxaparin. The ratio of the mean values of each studied biomarker in the ICU and the C-group was calculated. Biomarkers were classified in four clusters (Decrease, Stable, Slight Increase, Moderate Increase and High Increase).Results :The ICU-group consisted of 102 patients; 87% of these patients were admitted to the ICU directly from the emergency department. Males were 76 out of 102 patients. Age ranged from 30 to 93 years in the W-group. The changes of the biomarkers in patients with COVID-19 admitted at the ICU as compared to healthy individuals with are shown in Table 1. The ICU patients with COVID-19 were characterized by marked increase of IL-6 followed by increase of heparanase and D-dimers. The PPL-ct showed the most important decrease. Patients showed a significant decrease in FXII levels which was associated with a moderate increase of kininogen levels. The levels of the natural coagulation inhibitors as well as the clotting times (PT and aPTT) did not significantly modify in patients as compared to the controls. The rate of the propagation phase of thrombin generation (MRI) and the Peak of thrombin were significantly decrease and the lag-time was prolonged reflecting the antithrombotic effect of treatment with LMWH. Heparanse, free TFPI, and TM showed moderate or high increase. The decreased Ratio of TF/TFPI indicated that the free TFPI release dominated over the release of soluble TF activity.Conclusion: Patients with severe COVID-19 requiring ICU admission showed inhaled inflammatory reaction, hyperocoagulability and endothelial cell activation whereas platelet activation appeared to be secondary. Among the studied biomarkers the PPL-ct D-dimers and heparanase followed by TFPI, FvW, FM and TM levels appear to be mandatory for hypercoagulability of cellular origin. Interestingly patients with severe COVID-19 showed consumption of FXII indicating intrinsic clotting pathway activation and high levels of HK which also indicates endothelial cell activation. The clinical relevance of these biomarkers for early detection of hypercoagulability of cellular origin in patients with COVID-19 is being evaluated in prospective study.DisclosuresNo relevant conflicts of interest to declare.

Utilizing Plasma Composition Data to Help Determine Procoagulant Dynamics in Patients with Thermal Injury: A Computational Assessment.

The development of methods that generate individualized assessments of the procoagulant potential of burn patients could improve their treatment. Beyond its role as an essential intermediate in the formation of thrombin, factor (F)Xa has systemic effects as an agonist to inflammatory processes. In this study, we use a computational model to study the FXa dynamics underlying tissue factor-initiated thrombin generation in a small cohort of burn patients. Plasma samples were collected upon admission (Hour 0) from nine subjects (five non-survivors) with major burn injuries and then at 48 hours. Coagulation factor concentrations (II, V, VII, VIII, IX, X, TFPI, antithrombin (AT), protein C (PC)) were measured and used in a computational model to generate time course profiles for thrombin (IIa), FXa, extrinsic tenase, intrinsic tenase and prothrombinase complexes upon a 5 pM tissue factor stimulus in the presence of 1 nM thrombomodulin. Parameters were extracted from the thrombin and FXa profiles (including max rate (MaxRIIa and MaxRFXa) and peak level (MaxLIIa and MaxLFXa)). Procoagulant potential was also evaluated by determining the concentration of the complexes at select times. Parameter values were compared between survivors and non-survivors in the burn cohort and between the burn cohort and a simulation based on the mean physiological (100%) concentration for all factor levels. Burn patients differed at Hour 0 (p < 0.05) from 100% mean physiological levels for all coagulation factor levels except FV and FVII. The concentration of FX, FII, TFPI, AT and PC was lower; FIX and FVIII were increased. The composition differences resulted in all nine burn patients at Hour 0 displaying a procoagulant phenotype relative to 100% mean physiological simulation (MaxLIIa (306 ± 90 nM vs. 52 nM), MaxRIIa (2.9 ± 1.1 nM/s vs. 0.3 nM/s), respectively p < 0.001); MaxRFXa and MaxLFXa were also an order of magnitude greater than 100% mean physiological simulation (p < 0.001). When grouped by survival status and compared at the time of admission, non-survivors had lower PC levels (56 ± 18% vs. 82 ± 9%, p < 0.05), and faster MaxRFXa (29 ± 6 pM/s vs. 18 ± 6 pM/s, p < 0.05) than those that survived; similar trends were observed for all other procoagulant parameters. At 48 hours when comparing non-survivors to survivors, TFPI levels were higher (108 ± 18% vs. 59 ± 18%, p < 0.05), and MaxRIIa (1.5 ± 1.4 nM/s vs. 3.6 ± 0.7 nM/s, p < 0.05) and MaxRFXa (13 ± 12 pM/s vs. 35 ± 4 pM/s, p < 0.05) were lower; similar trends were observed with all other procoagulant parameters. Overall, between admission and 48 hours, procoagulant potential, as represented by MaxR and MaxL parameters for thrombin and FXa, in non-survivors decreased while in survivors they increased (p < 0.05). In patients that survived, there was a positive correlation between FX levels and MaxLFXa (r = 0.96) and reversed in mortality (r= -0.91). Thrombin and FXa generation are increased in burn patients at admission compared to mean physiological simulations. Over the first 48 hours, burn survivors became more procoagulant while non-survivors became less procoagulant. Differences between survivors and non-survivors appear to be present in the underlying dynamics that contribute to FXa dynamics. Understanding how the individual specific balance of procoagulant and anticoagulant proteins contributes to thrombin and FXa generation could ultimately guide therapy and potentially reduce burn injury-related morbidity and mortality.

Factors Associated with Low Admission Platelet Count in Adults with Acute Aortic Dissection.

Purpose: Platelets are crucial components of the coagulation processes, and low admission platelet count (PLC) is associated with adverse clinical outcomes in patients with Stanford type A acute aortic dissection (AAD).Methods: A total of 130 consecutive patients undergoing Stanford type A AAD surgery in Beijing Anzhen Hospital were enrolled between January 2013 and July 2014. Preoperative clinical and laboratory data from patients were collected. Multiple regression analyses were used to determine the independent factors of low admission platelets.Results: Adjusted multiple regression analysis showed that age (β: −1.069, 95% confidence interval [CI]: −2.109, −0.029), sex (β: −29.973, 95% CI: −56.512, −3.433), tissue factor pathway inhibitor (TFPI; β: 0.197, 95% CI: 0.039, 0.354), fibrinogen degradation product (FDP) (β: −0.476, 95% CI: −0.879, −0.074), and attack time (β: 11.125, 95% CI: 7.963, 14.287) were significantly associated with admission PLC. Admission PLC increased with attack time up to the 3 days (β: 16.2, 95% CI: 12.1, 20.2).Conclusions: We found that increasing age, male patients, patients with lower serum levels of TFPI and higher serum levels of FDP, and patients with a shorter attack time were significantly associated with lower PLC at admission. Moreover, the turning point of attack time is 3 days after the onset of dissection.