The risk of a first and a recurrent venous thrombosis associated with an elevated D-dimer level and an elevated thrombin potential: results of the THE-VTE study

Thrombin Generation Is Associated with Venous Thromboembolism Recurrence, but Not with Major Bleeding and Death in the Elderly: A Prospective Multicenter Cohort Study

It is currently unknown whether thrombin generation is associated with venous thromboembolism (VTE) recurrence, major bleeding, or mortality in the elderly. Therefore, our aim was to prospectively study the association between thrombin generation and VTE recurrence, major bleeding, and mortality in elderly patients with acute VTE. Consecutive patients aged ≥65 years with acute VTE were followed for 2 years, starting from 1 year after the index VTE. Primary outcomes were VTE recurrence, major bleeding, and mortality. Thrombin generation was assessed in 551 patients 1 year after the index VTE. At this time, 59% of the patients were still anticoagulated. Thrombin generation was discriminatory for VTE recurrence, but not for major bleeding and mortality in non-anticoagulated patients. Moreover, peak ratio (adjusted subhazard ratio 4.09, 95% CI, 1.12-14.92) and normalized peak ratio (adjusted subhazard ratio 2.18, 95% CI, 1.28-3.73) in the presence/absence of thrombomodulin were associated with VTE recurrence, but not with major bleeding and mortality after adjustment for potential confounding factors. In elderly patients, thrombin generation was associated with VTE recurrence, but not with major bleeding and/or mortality. Therefore, our study suggests the potential usefulness of thrombin generation measurement after anticoagulation completion for VTE to help identify among elderly patients those at higher risk of VTE recurrence.

Elevated plasma complement factor H related 5 protein is associated with venous thromboembolism

Venous thromboembolism (VTE) is a common, multi-causal disease with potentially serious short- and long-term complications. In clinical practice, there is a need for improved plasma biomarker-based tools for VTE diagnosis and risk prediction. Here we show, using proteomics profiling to screen plasma from patients with suspected acute VTE, and several case-control studies for VTE, how Complement Factor H Related 5 protein (CFHR5), a regulator of the alternative pathway of complement activation, is a VTE-associated plasma biomarker. In plasma, higher CFHR5 levels are associated with increased thrombin generation potential and recombinant CFHR5 enhanced platelet activation in vitro. GWAS analysis of ~52,000 participants identifies six loci associated with CFHR5 plasma levels, but Mendelian randomization do not demonstrate causality between CFHR5 and VTE. Our results indicate an important role for the regulation of the alternative pathway of complement activation in VTE and that CFHR5 represents a potential diagnostic and/or risk predictive plasma biomarker.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Translational insights into mechanisms underlying residual venous obstruction and the role of factor XI, P-selectin and GPVI in recurrent venous thromboembolism

BACKGROUND

Residual venous obstruction (RVO) after deep vein thrombosis (DVT) is considered a risk factor of recurrent venous thromboembolism (VTE), arterial events and post-thrombotic syndrome (PTS). We hypothesized thrombo-inflammatory markers might be associated with RVO and clinical outcomes.

MATERIALS AND METHODS

In a DVT cohort with routine RVO-assessment and 5-year follow-up, patients were invited for blood withdrawal after stopping anticoagulants. Thrombin generation potential, coagulation enzyme:inhibitor complexes, soluble platelet markers and clinical markers were measured in platelet-poor plasma. Associations were represented as odds ratio (OR) or hazard ratio (HR) per standard deviation.

RESULTS

Patients with RVO (102/306, 33 %) had higher rates of PTS (24 vs. 12 %, p = 0.008), but similar rates of recurrence (16 vs. 15 %, p = 0.91) and arterial events (7 vs. 4 %, p = 0.26). RVO was associated with thrombin peak height (OR 1.40 [1.04-1.88]), endogenous thrombin potential (ETP, OR 1.35 [1.02-1.79]), and CRP (OR 1.74 [1.10-2.75]). Recurrent VTE was associated with ETP (HR 1.36 [1.03-1.81]), FXIa:C₁-inhibitor (HR 1.34 [1.04-1.72]), thrombin:antithrombin (HR 1.36 [1.16-1.59]), soluble P-selectin (HR 2.30 [1.69-3.11]), soluble glycoprotein VI (sGPVI, HR 1.30 [1.01-1.69]), D-dimer (HR 1.56 [1.31-1.86]), and factor VIII (HR 1.44 [1.15-1.82]). Arterial events were associated with sGPVI (HR 1.80 [1.25-2.59]). PTS was not associated with any marker.

CONCLUSIONS

Our findings indicate RVO was associated with thrombo-inflammation, but this did not predict clinical outcomes in this setting. Importantly, we found recurrent VTE was associated with ongoing coagulation and platelet activation in patients well beyond the acute phase of DVT. Furthermore, sGPVI indicated an increased risk of arterial events, highlighting the role of platelets in arterial thrombosis following DVT.

Association Between the Severity of Obstructive Sleep Apnea and the Risk Stratification of Acute Pulmonary Embolism

Obstructive sleep apnea (OSA) has been associated with the initiation and progression of cardiovascular disease. This study aimed to explore the relationship between the severity of OSA and the risk stratification of acute pulmonary embolism (PE). In this single-center cohort study, patients diagnosed with PE were evaluated for OSA via polygraphy monitoring. The simplified PE severity index (sPESI) and the number of patients requiring systemic thrombolysis were used to determine the severity of the disease. Echocardiography was performed on all participants. All patients were divided into 2 groups (OSA group and non-OSA group), and the patients in OSA group were then divided into 3 groups based on the severity of OSA. Patients with severe OSA had a significantly higher number of patients with sPESI ≥ 1 (P = .005). A higher proportion of patients with severe OSA require systemic thrombolysis (P = .010). Patients with apnea-hypopnea index (AHI) > 30/h had a much higher fibrinogen (P = .004) and D-dimer (P = .040) level than those in the non-OSA group. The levels of creatinine were significantly higher in patients with OSA (P = .040). Echocardiography showed a significant difference in left ventricular ejection fraction (LVEF) between patients in non-OSA and severe OSA groups (P = .035). And brain natriuretic peptide (BNP) also exhibited a progressive worsening related to the deepest desaturation and oxygen desaturation index. OSA, especially with AHI > 30/h, is correlated with the severity and prognosis of acute PE. This might be attributed to the prothrombotic effect, renal impairment, and cardiac dysfunction in patients with severe OSA.

Haemostatic alterations and management of haemostasis in patients with cirrhosis

Patients with cirrhosis frequently acquire complex changes in their haemostatic system including a decreased platelet count and decreased levels of various haemostatic proteins. Although historically patients with cirrhosis were thought to have a haemostasis-related bleeding tendency, it is now widely accepted that the haemostatic system of patients with cirrhosis remains in balance as a result of simultaneous changes in pro- and anti-haemostatic systems. The concept of rebalanced haemostasis has led to changes in clinical management, although firm evidence from well-designed clinical studies is largely lacking. For example, many invasive procedures in patients with cirrhosis and a prolonged prothrombin time are now performed without prophylaxis with fresh frozen plasma. Conversely, clinicians have become more aware of the need for anti-thrombotic therapy, even in those patients with abnormal routine coagulation tests. This paper will outline recent advances in pathogenesis, prevention and treatment of both bleeding and thrombotic complications in patients with cirrhosis. Among other topics, we will discuss the haemostatic status of acutely ill patients with cirrhosis, the various causes of bleeding in patients with cirrhosis, and how best to prevent or treat bleeding. In addition, we will discuss the hypercoagulable features of patients with cirrhosis, new insights into the pathogenesis of portal vein thrombosis, and how best to prevent or treat thromboses.

Plasma levels of platelet-derived microvesicles are associated with risk of future venous thromboembolism

BACKGROUND

Microvesicles (MVs) are small double-membrane encapsulated particles shed from cells. Case-control studies have reported elevated plasma levels of platelet-derived MVs (PDMVs) in patients with venous thromboembolism (VTE). However, it is not known whether high PDMV levels is a risk factor or a consequence of the acute VTE event.

OBJECTIVES

To investigate the association between PDMVs in plasma and risk of future incident VTE.

METHODS

We performed a population-based nested case-control study with 314 VTE cases and 705 age- and sex-matched controls (from The Tromsø Study) to investigate the association between the proportion of PDMVs (PDMVs%) in plasma and risk of future incident VTE. MVs isolated from plasma sampled at baseline (i.e., before VTE) were stained for platelet markers and analyzed by flow cytometry. PDMVs% were defined as the number of PDMVs divided by the total number of MVs. Odds ratios (ORs) with 95% confidence intervals (CI) for VTE risk were estimated across quartiles of PDMVs%.

RESULTS

Subjects with PDMVs% in the highest quartile had an OR for VTE of 1.78 (95% CI: 1.21-2.64) and 1.99 (95% CI: 1.24-3.26) for provoked VTE, compared to those in the lowest quartile. The association was moderately affected by multivariable adjustment for age, sex, body mass index, C-reactive protein, platelet count, and cancer. The OR for VTE was higher when the time between blood sampling and event was shorter.

CONCLUSIONS

Our results show that high proportions of PDMVs are associated with future risk of incident VTE and imply a role of platelet activation in the pathogenesis of VTE.

The influence of corn trypsin inhibitor on the contribution of coagulation determinants to the Technoclone Thrombin Generation Assay (TGA) and the Calibrated Automated Thrombogram (CAT)

In thrombin generation (TG) assays, regarded as global coagulation tests, contact activation is considered a major problem which can be eliminated by adding Corn Trypsin Inhibitor (CTI). In previous studies, however, venous thrombosis risk prediction using TG assays did not improve after CTI addition. However, it is unknown whether CTI addition could help to detect subtle but relevant nuances in determinants of TG, making the assay more suitable to detect disturbances in the coagulation system. This study’s objective was to assess whether the addition of CTI is associated with a broader contribution of individual coagulation factors to the total amount of thrombin formed in Calibrated Automated Thrombogram (CAT) and Technoclone Thrombin Generation Assay (TGA). Thrombin generation was measured in 326 healthy individuals from THE VTE study at very low tissue factor concentrations, with and without addition of CTI prior to blood sampling. The influence of several coagulation factors on total amount of thrombin formed, i.e. area under the curve (AUC) or endogenous thrombin potential (ETP), was analysed using multiple linear regression with standardisation of all values resulting in Z-scores with 95% confidence intervals (95%CI). Association between coagulation factors and TG changed minimally after addition of CTI. Largest changes after CTI addition were found for following factors: for CAT: free protein S (from 0.00 (95%CI -0.12 to 0.12) to -0.29 (95%CI -0.43 to -0.15)) and protein S (from -0.05 (95%CI -0.18 to 0.08) to -0.21 (95%CI -0.37 to -0.05)); for TGA: antithrombin (from -0.11 (-0.23 to 0.02) to -0.19 (-0.30 to -0.07)), factor VIII (from 0.15 (0.03 to 0.27) to 0.24 (0.13 to 0.36)) and fibrinogen (from 0.12 (-0.01 to 0.26) to 0.19 (0.06 to 0.32)). In conclusion, there is no clear trend towards a broader contribution of coagulation factors in samples handled with CTI compared with those handled without CTI.

DNase 1 Protects From Increased Thrombin Generation and Venous Thrombosis During Aging: Cross-Sectional Study in Mice and Humans

Background Human aging is associated with increased risk of thrombosis, but the mechanisms are poorly defined. We hypothesized that aging induces peroxide-dependent release of neutrophil extracellular traps that contribute to thrombin generation and thrombosis. Methods and Results We studied C57BL6J mice and littermates of glutathione peroxidase-1 transgenic and wild-type mice at young (4 month) and old (20 month) ages and a healthy cohort of young (18-39 years) or middle-aged/older (50-72 years) humans. In plasma, we measured thrombin generation potential and components of neutrophil extracellular traps (cell-free DNA and citrullinated histone). Aged wild-type mice displayed a significant increase in thrombin generation that was decreased in aged glutathione peroxidase-1 transgenic mice. Both aged wild-type and aged glutathione peroxidase-1 transgenic mice demonstrated similar elevation of plasma cell-free DNA compared with young mice. In contrast, plasma levels of citrullinated histone were not altered with age or genotype. Release of neutrophil extracellular traps from neutrophils in vitro was also similar between young and aged wild-type or glutathione peroxidase-1 transgenic mice. Treatment of plasma or mice with DNase 1 decreased age-associated increases in thrombin generation, and DNase 1 treatment blocked the development of experimental venous thrombi in aged C57BL6J mice. Similarly, thrombin generation potential and plasma cell-free DNA, but not citrullinated histone, were higher in middle-aged/older humans, and treatment of plasma with DNase 1 reversed the increase in thrombin generation. Conclusions We conclude that DNase 1 limits thrombin generation and protects from venous thrombosis during aging, likely by hydrolyzing cell-free DNA.

Clinical use of thrombin generation assays

Determining patient's coagulation profile, i.e. detecting a bleeding tendency or the opposite, a thrombotic risk, is crucial for clinicians in many situations. Routine coagulation assays and even more specialized tests may not allow a relevant characterization of the hemostatic balance. In contrast, thrombin generation assay (TGA) is a global assay allowing the dynamic continuous and simultaneous recording of the combined effects of both thrombin generation and thrombin inactivation. TGA thus reflects the result of procoagulant and anticoagulant activities in blood and plasma. Because of this unique feature, TGA has been widely used in a wide array of settings from both research, clinical and pharmaceutical perspectives. This includes diagnosis, prognosis, prophylaxis, and treatment of inherited and acquired bleeding and thrombotic disorders. In addition, TGA has been shown to provide relevant information for the diagnosis of coagulopathies induced by infectious diseases, comprising also disturbance of the coagulation system in COVID-19, or for the assessment of early recurrence in breast cancer. This review article aims to document most clinical applications of TGA.

Plasma procoagulant phospholipid clotting time and venous thromboembolism risk

BACKGROUND

Negatively charged procoagulant phospholipids, phosphatidylserine (PS) in particular, are vital to coagulation and expressed on the surface membrane of extracellular vesicles. No previous study has investigated the association between plasma procoagulant phospholipid clotting time (PPLCT) and future risk of venous thromboembolism (VTE).

OBJECTIVES

To investigate the association between plasma PPLCT and the risk of incident VTE in a nested case-control study.

METHODS

We conducted a nested case-control study in 296 VTE patients and 674 age- and sex-matched controls derived from a general population cohort (The Tromsø Study 1994-2007). PPLCT was measured in platelet-free plasma using a modified factor Xa-dependent clotting assay. Logistic regression was used to estimate odds ratio (OR) with 95% confidence intervals (CI) for VTE with PPLCT modelled as a continuous variable across quartiles and in dichotomized analyses.

RESULTS

There was a weak inverse association between plasma PPLCT and risk of VTE per 1 standard deviation increase of PPLCT (OR 0.93, 95% CI 0.80-1.07) and when comparing those with PPLCT in the highest quartile (OR 0.89, 95% CI 0.60-1.30) with those in the lowest quartile. Subjects with PPLCT >95th percentile had substantially lowered OR for VTE (OR 0.35, 95% CI 0.13-0.81). The inverse association was stronger when the analyses were restricted to samples taken shortly before the event. The risk estimates by categories of plasma PPLCT were similar for deep vein thrombosis and pulmonary embolism.

CONCLUSION

Our findings suggest that high plasma PPLCT is associated with reduced risk of VTE.

Resistance to activated protein C and impaired TFPI activity in women with previous hormone-induced venous thromboembolism

INTRODUCTION

Hormonal contraception is a well-known risk factor for venous thromboembolism (VTE). APC resistance and impaired functions of protein S and TFPI are thought to play an important role in the pathogenesis of hormone-related VTE. It is unknown, whether women, who develop VTE during hormonal contraception possess a vulnerability in these pathways, making them susceptible to thrombosis.

MATERIALS AND METHODS

Plasma samples were obtained from 57 premenopausal women in average 15.3 years after hormone-associated VTE and from 31 healthy controls. Thrombin generation at high tissue factor (TF) in the absence and in the presence of activated protein C (APC) and at low TF without and with inhibiting anti-protein S- and anti-TFPI-antibodies was measured via calibrated automated thrombography.

RESULTS

Women with previous hormone-related thrombosis had higher thrombin generation at low TF, higher APC resistance, protein S- and TFPI ratios, differences: 219.9 nM IIa.min (95%CI:90.4 to 349.3); 1.88 (95%CI:0.71 to 3.05); 0.13 (95%CI:0.01 to 0.26) and 0.19 (95%CI:0.08 to 0.30), respectively. Thrombin generation at high TF without APC did not differ between the groups. Smoking decreased thrombin generation at low TF by -222.6 nM IIa.min (95%CI: -381.1 to -64.1), the APC sensitivity ratio by -2.20 (95%CI: -3.63 to -0.77) and the TFPI ratio by -0.16 (95%CI: -0.29 to -0.03), but did not influence thrombin generation at high TF.

DISCUSSION

We demonstrated impairment of the protein S/TFPI system and increased APC resistance in women with previous hormone-induced VTE. Smoking decreased thrombin generation at assay conditions, dependent on the function of the TFPI system.

The modification of the thrombin generation assay for the clinical assessment of hypercoagulability in patients receiving heparin therapy

BACKGROUND

Heparin diminishes thrombin generation (TG) because it decreases the survival time of thrombin in plasma. Under heparin therapy, the TG curve therefore does not reflect the true hemostatic status of the patient.

AIM

We investigated how far the in vitro addition of a heparin antagonist can restore the underlying TG capacity.

MATERIALS & METHODS

Five different heparin antagonists were tested: polybrene, protamine sulfate, heparinase type 1, heparinase HEP-TEM, and (Z-GGR)₂ -rhodamine (P2Rho).

RESULTS AND CONCLUSION

Polybrene, P2Rho, and heparinase HEP-TEM effectively neutralized heparin at prophylactic and therapeutical doses of both low molecular weight and unfractionated heparin. The advantages and limits of each molecule and the most favorable combinations of TG-trigger and antagonist are discussed.

Second consensus document on diagnosis and management of acute deep vein thrombosis: updated document elaborated by the ESC Working Group on aorta and peripheral vascular diseases and the ESC Working Group on pulmonary circulation and right ventricular function

This consensus document is proposed to clinicians to provide the whole spectrum of deep vein thrombosis management as an update to the 2017 consensus document. New data guiding clinicians in indicating extended anticoagulation, management of patients with cancer, and prevention and management of post-thrombotic syndrome are presented. More data on benefit and safety of non-vitamin K antagonists oral anticoagulants are highlighted, along with the arrival of new antidotes for severe bleeding management.

Diagnostic accuracy of D-Dimer testing for recurrent venous thromboembolism: A systematic review with meta-analysis.: VTE recurrence and D-dimer

OBJECTIVE

Venous thromboembolism (VTE) recurrence is a major concern after a first symptomatic episode, potentially impacting survival and healthcare needs in community, hospital and rehabilitation settings. We evaluated the association of D-Dimer positivity after oral anticoagulant therapy (OAT) discontinuation with VTE recurrence.

METHODS

PubMed, Web of Science, Scopus and EMBASE databases were systematically searched. Differences were expressed as Odds Ratio (OR) with 95% confidence intervals (95%CI). Pooled sensitivity, specificity, positive (PLR) and negative likelihood ratio (NLR), and summary ROC (sROC) curve were calculated.

RESULTS

Twenty-six articles on 10,725 VTE patients showed that the absolute risk of recurrence was 16.1% (95%CI: 13.2%-19.5%) among 4,049 patients with a positive D-Dimer and 7.4% (95%CI: 6.0%-9.0%) in 6,676 controls (OR: 2.1, 95%CI: 1.7-2.8, P<0.001), with an attributable risk of 54.0%. sROC curve of the association between positive D-Dimer and recurrence showed a diagnostic AUC of 63.8 (95%CI: 60.3-67.4), with a pooled sensitivity of 54.3% (95%CI: 51.3%-57.3%), specificity of 64.2% (95%CI: 63.2-65.1), PLR of 1.53 (95%CI: 1.37-1.72), and NLR of 0.71 (95%CI: 0.60-0.84). Subgroup and meta-regression analyses suggested that a positive D-Dimer may have a higher discriminatory ability for patients with provoked events, confirmed by better pooled diagnostic indexes for recurrence and a diagnostic AUC of 70.6 (95%CI: 63.8-77.4). Regression models showed that the rate of OAT resumption after the evidence of D-Dimer positivity was inversely associated with VTE recurrence (Z-score: -3.91, P<0.001).

CONCLUSIONS

D-Dimer positivity after OAT may identify VTE patients at higher risk of recurrence, with a better diagnostic accuracy for provoked events.

D-dimer, thrombin generation, and risk of a first venous thrombosis in the elderly

BACKGROUND

A high D-dimer level and parameters of the thrombin generation (TG) potential are associated with the risk of a first venous thrombosis (VT) in young and middle-aged populations.

OBJECTIVES

To investigate whether D-dimer and TG potential (lag-time, time-to-peak [ttPeak], peak thrombin, endogenous thrombin potential [ETP], and velocity index), are associated with the risk of a first VT in those aged 70 years and older.

METHODS

We included 215 patients with a first VT and 358 controls, all aged >70 years, from the Age and Thrombosis, Acquired and Genetic Risk Factors in the Elderly (AT-AGE) study. To assess the risk of VT, odds ratios with 95% confidence intervals (CIs) were estimated using logistic regression analysis.

RESULTS

D-dimer and all TG parameters except lag time were associated with an increased risk of VT in a dose-response manner. Comparing the fourth with the first quartile (for ttPeak comparing the first with the fourth quartile), risk estimates were: 7.8 (95% CI, 4.0-15.0) for peak, 2.0 (95% CI, 1.2-3.3) for ttPeak, 9.1 (95% CI, 4.4-18.9) for ETP, and 11.5 (95% CI, 5.7-23.3) for velocity index. Comparing the highest quartile of D-dimer with the lowest, the risk was 7.7-fold increased (95% CI, 4.0-14.8). Furthermore, all factors also increased the risk of VT after dichotomizing at more extreme cutoff values. The risk of VT was further increased in the presence of multiple prothrombotic TG parameters and elevated D-dimer level or in combination with prothrombotic mutations.

CONCLUSIONS

D-dimer and TG parameters (except lag time) are associated with the risk of first VT in elderly population.

Pro-coagulant imbalance in patients with community acquired pneumonia assessed on admission and one month after hospital discharge

OBJECTIVES

Patients hospitalized because of community-acquired-pneumonia (CAP) are at risk of cardiovascular diseases. Although plasma procoagulant imbalance play a role, mechanisms are not completely understood. We aimed to investigate whether there is a measurable state of procoagulant imbalance following inflammation determined by CAP.

METHODS

We analyzed blood from 51 CAP patients at admission and 51 healthy subjects (HS) for (i) pro and anticoagulants, (ii) thrombin generation (TG) with or without thrombomodulin (TM), which is the physiologic activator of the protein C anticoagulant pathway and(iii) by assessing the ratio between von Willebrand-factor (VWF) and its protease ADAMTS13. Thirty patients were re-analyzed one month after discharge when CAP was resolved.

RESULTS

Median levels of TG parameters, including the endogenous thrombin potential (ETP), the ETP-TM-ratio (with/without TM), peak-thrombin and velocity index were higher in patients at baseline than HS. In particular, the median (IQR) ETP-TM-ratio in patients vs. HS was 0.88 (0.83-0.91) vs. 0.63 (0.48-0.71), p<0.001. Factor (F)VIII, a potent procoagulant involved in TG was higher in patients at baseline than HS [195 U/dL (100-388) vs. 127(108-145)], p<0.001]. The ratio of VWF/ADAMTS13 was higher at baseline than HS. Cumulatively, the findings indicate a state of pro-coagulant imbalance, which (although reduced), remained high [i.e., ETP-TM-ratio, 0.80 (0.74-0.84); FVIII, 152 U/dL (122-190)] one month after discharge when the infection was resolved.

CONCLUSIONS

Patients with CAP possess a state of pro-coagulant imbalance, which remains substantially high, even when the infection is resolved. The findings suggest CAP patients as candidates for antithrombotic prophylaxis even after the resolution of infection. Clinical trials are warranted to assess the benefit/risk ratio of prophylaxis extension.

[Thrombin generation assay in autoimmune disease]

Thrombin generation assay (TGA) is a useful tool to evaluate the initiation, propagation and inhibition of coagulation. TGA is a global test that is used to assess hemorrhagic risk in hemophilia patients, but it can also be used to study hypercoagulable states. The interest of TGA is to screen for cardiovascular risk, which is regularly associated with autoimmune disease (AID) such as antiphospholipid syndrome. Indeed, TGA has been used to evaluate hypercoagulability in patients with antiphospholipid syndrome treated with rivaroxaban versus warfarin. In other AIDs without thrombotic events, TGA measurement is elevated, mainly in rheumatoid arthritis (RA), systemic lupus erythematosus and Behçet's disease. These findings in RA are correlated with the inflammatory activity of the disease. In systemic lupus erythematosus and Behçet's disease, TGA appears to reflect disease activity. In conclusion, TGA remains relatively under used in the clinical evaluation of AID, but it could play a greater role in the evaluation of certain potentially thrombogenic treatments in AID. Finally, TGA helps measuring AID activity, due to the clearlink between coagulation and inflammation, despite some limitations of interpretation mainly due to a lack of standardization.

Psoriatic disease is associated with systemic inflammation, endothelial activation, and altered haemostatic function

Psoriasis is a chronic, immune-mediated inflammatory skin disease, affecting approximately 2% of the general population, which can be accompanied by psoriatic arthritis (PsA). The condition has been associated with an increased cardiovascular burden. Hypercoagulability is a potential underlying mechanism that may contribute to the increased risk of major cardiovascular events in psoriatic individuals. Whole blood samples were collected from 20 PsA patients and 20 healthy individuals. The concentrations of inflammatory molecules (C-reactive protein, serum amyloid A, soluble intercellular adhesion molecule-1, soluble vascular cell adhesion molecule-1, and soluble P-selectin) were determined by enzyme-linked immunosorbent assays. In addition, clotting efficiency was evaluated by thromboelastography. The fibrin network architecture was also assessed by scanning electron microscopy. Elevated levels of circulating inflammatory molecules were significantly associated with the presence of psoriatic disease. Furthermore, an increased tendency towards thrombus formation was significantly predictive of disease presence. Scanning electron microscopy revealed that fibrin clots were denser in psoriatic individuals, compared to healthy controls, with an increased fibrin fibre diameter associated with psoriatic disease. Our results add to the accumulating evidence of the systemic nature of psoriasis and the subsequent risk of cardiovascular comorbidities, potentially due to an acquired hypercoagulability. We suggest that haemostatic function should be monitored carefully in psoriatic patients that present with severe disease, due to the pre-eminent risk of developing thrombotic complications.

Thrombin: A Pivotal Player in Hemostasis and Beyond

The serine protease thrombin, a naturally derived enzyme, plays a key role in hemostasis by converting fibrinogen to fibrin and activating coagulation factor XIII whereby the fibrin clot is stabilized. Furthermore, thrombin activates platelets through protease-activated receptors on the platelet surface. Conversely, thrombin also exerts anticoagulant effects, enhancing the protein C activity while complexed with thrombomodulin. During recent years, it has become evident that thrombin has significant effects beyond hemostasis, as it contributes also to modulation of the endothelium, promotes inflammation and angiogenesis, and plays a role in tumor progression. Yet, due to the very short half-life and almost immediate inhibition in fluid phase by antithrombin, thrombin itself remains elusive, and only indirect measurement of thrombin generation is possible. This review provides a description of structure and mechanisms of action of thrombin both in physiological and pathological processes. Furthermore, it summarizes laboratory tests that measure in vivo or ex vivo thrombin generation, and presents knowledge on the value of these biomarkers in bleeding disorders, cardiopulmonary bypass surgery, and thromboembolic risk assessment in different patient populations. Finally, this review outlines further perspectives on using thrombin generation biomarkers for research purposes and in clinical practice.

Homocysteine is potential serological marker for predicting the risk of deep venous thrombosis of the lower extremities in patients received operation of lower limb fracture

Objective

The aim of the study is to investigate the correlations among serum homocysteine (Hcy), D-dimer, and the risk of developing deep venous thrombosis (DVT) of the lower extremities in patients who underwent operation for lower limb fracture.

Methods

Seventy-five cases who underwent operation for lower limb fracture were included and further divided into DVT group (n = 26) and control group (n = 49) based on post-DVT diagnostic criteria. The serum Hcy and D-dimer were examined 48 h after operation. The serum Hcy and D-dimer levels were compared between the two groups. The correlation between serum Hcy and D-dimer was investigated by the Pearson correlation test. The receiver-operating characteristic (ROC) curve was applied to evaluate the diagnostic performance of serum Hcy and D-dimer as serological markers for DVT.

Results

The serum Hcy concentrations were 11.96 ± 3.98 μmol/L and 7.92 ± 3.27 μmol/L for DVT and control groups, respectively, with statistical difference (t = 4.72, P < 0.01). The serum D-dimer in the DVT group was significantly higher than that of the control group (8.99 ± 4.50 vs 1.70 ± 2.11) μg/mL with statistical difference (t = 9.56, P < 0.01). Line regression analysis indicated that serum Hcy was positively correlated with serum D-dimer concentration and can be demonstrated by the equation of Y = 0.6651*X + 1.036 for the DVT group. Using serum Hcy as the biomarker for predicting DVT, the prediction sensitivity and specificity were 76.92 and 71.44%, respectively, with the AUC of 0.7804 under the cut-point of 9.54 μmol/L. For serum D-dimer, the prediction sensitivity and specificity were 96.15 and 73.47%, respectively, with the area under the ROC (AUC) of 0.9455 under the cut-point of 1.66 μg/mL.

Conclusion

Serum Hcy was significantly elevated in DTV patients, and hence, it can be applied as a serological marker for DVT prediction in patients who underwent operation for lower limb fracture. However, the DVT prediction performance of serum Hcy was inferior to D-dimer especially for diagnostic sensitivity.

Shedding Light on Hemostasis in Patients With Inflammatory Bowel Diseases

Patients with inflammatory bowel diseases (IBD) have an increased risk of thrombosis, possibly due to changes in blood cells and molecules involved in hemostasis. They have increased platelet counts and reactivity as well as increased platelet-derived large extracellular vesicles. Coagulation is continuously activated in patients with IBD, based on measured markers of thrombin generation, and the anticoagulant functions of endothelial cells are damaged. Furthermore, fibrinogen is increased and fibrin clots are denser. However, pathogenesis of thrombosis in patients with IBD appears to differ from that of patients without IBD. Patients with IBD also take drugs that might contribute to risk of thrombosis, complicating the picture. We review the features of homeostasis that are altered in patients with IBD and possible mechanisms of this relationship.

VWF/ADAMTS13 Imbalance, But Not Global Coagulation or Fibrinolysis, Is Associated With Outcome and Bleeding in Acute Liver Failure

BACKGROUND AND AIMS

Recent studies of acute liver failure (ALF) in man and animals have suggested that rebalanced hemostasis occurs, with distinct hypercoagulable features clinically evidenced by a low risk of bleeding. Rodent models have shown a link between intrahepatic microthrombus formation and progression of ALF. We sought to confirm these earlier findings in a large series of patients with well-characterized ALF from the Acute Liver Failure Study Group.

APPROACH AND RESULTS

Citrated plasma samples taken on admission from 676 patients with ALF or acute liver injury (international normalized ratio ≥2.0 without hepatic encephalopathy) were used to determine levels of von Willebrand factor (VWF), a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13) activity, thrombomodulin-modified thrombin generation, and clot lysis time (CLT) and compared with the levels in 40 healthy controls. Patients had 3-fold increased VWF levels, 4-fold decreased ADAMTS13 activity, similar thrombin generating capacity, and 2.4-fold increased CLT, compared with controls. Increasing disease severity was associated with progressively more elevated VWF levels as well as hypofibrinolysis. Patients who died or underwent liver transplantation within 21 days of admission had higher VWF levels, lower ADAMTS13 activity, but similar thrombin generation and a similar proportion of patients with severe hypofibrinolysis, when compared with transplant-free survivors. Likewise, patients with bleeding complications had higher VWF levels and lower ADAMTS13 activity compared to those without bleeding. Thrombin generation and CLT did not differ significantly between bleeding and nonbleeding patients.

CONCLUSIONS

Rebalanced hemostatic status was confirmed in a large cohort of patients with acute liver injury/ALF, demonstrating that VWF/ADAMTS13 imbalance is associated with poor outcome and bleeding. The association between VWF/ADAMTS13 imbalance and bleeding suggests that bleeding in ALF relates more to systemic inflammation than a primary coagulopathy.

Agreement of aptamer proteomics with standard methods for measuring venous thrombosis biomarkers

BACKGROUND

Venous thromboembolism (VTE) is a complex disease with an incidence rate of about 1 in 1000 per year. Despite the availability of validated biomarkers for VTE, unprovoked events account for 50% of first events. Therefore, emerging high-throughput proteomics are promising methods for the expansion of VTE biomarkers. One such promising high-throughput platform is SomaScan, which uses a large library of synthetic oligonucleotide ligands known as aptamers to measure thousands of proteins.

OBJECTIVE

The aim of this study was to evaluate the viability of the aptamer-based SomaScan platform for VTE studies by examining its agreement with standard laboratory methods.

METHODS

We examined the agreement between eight established VTE biomarkers measured by SomaScan and standard laboratory immunoassay and viscosity-based instruments in 54 individuals (27 cases and 27 controls) from the Thrombophilia, Hypercoagulability and Environmental Risks in Venous Thromboembolism study. We performed the agreement analysis by using a regression model and predicting the estimates and the 95% prediction interval (PI) of the laboratory instrument values using SomaScan values.

RESULTS

SomaScan measurements exhibited overall poor agreement, particularly for D-dimer (average fit, 492.7 ng/mL; 95% PI, 110.0-1998.2) and fibrinogen (average fit, 3.3 g/L; 95% PI, 2.0-4.7).

CONCLUSION

Our results indicate that SomaScan measurement had poor agreement with the standard laboratory measurements. These results may explain why some genome-wide association studies with VTE proteins measured by SomaScan did not confirm previously identified loci. Therefore, SomaScan should be considered with caution in VTE studies.

Combination of D-dimer and simplified pulmonary embolism severity index to improve prediction of hospital death in patients with acute pulmonary embolism

Objective

To investigate whether the combination of D-dimer and simplified pulmonary embolism severity index (sPESI) could improve prediction of in-hospital death from pulmonary embolism (PE).

Methods

Patients with PE (n = 272) were divided into a surviving group (n = 249) and an in-hospital death group (n = 23).

Results

Compared with surviving patients, patients who died in hospital had significantly higher rates of hypotension and tachycardia, reduced SaO₂ levels, elevated D-dimer and troponin T levels, higher sPESI scores, and were more likely to be classified as high risk. Elevated D-dimer levels and high sPESI scores were significantly associated with in-hospital death. Using thresholds for D-dimer and sPESI of 3.175 ng/mL and 1.5, respectively, the specificity for prediction of in-hospital death was 0.357 and 0.414, respectively, and the area under the receiver operating characteristic curve (AUC) was 0.665 and 0.668, respectively. When D-dimer and sPESI were considered together, the specificity for prediction of in-hospital death increased to 0.838 and the AUC increased to 0.74.

Conclusions

D-dimer and sPESI were associated with in-hospital death from PE. Considering D-dimer levels together with sPESI can significantly improve the specificity of predicting in-hospital death for patients with PE.

Nephrotic syndrome disease activity is proportional to its associated hypercoagulopathy

INTRODUCTION

Nephrotic syndrome (NS) is associated with an acquired hypercoagulopathy that drives its strong predilection for life-threatening thrombosis. We previously demonstrated that hypercoagulopathy is proportional to NS disease severity in animal models. Therefore, hypercoagulopathy and disease severity may inform thrombosis risk and better guide therapeutic decision making. The objective of this study was thus to establish the relationship between disease severity and hypercoagulopathy in human NS.

MATERIALS AND METHODS

Thrombin generation assays (TGA) were performed on biorepository plasma samples from a prospective longitudinal NS cohort study. TGA was also determined on a separate cohort of incident NS patients. Multivariable regression was used to build NS-hypercoagulopathy relationship models.

RESULTS

Endogenous thrombin potential (ETP) was the TGA parameter most strongly correlated with NS severity and was proportional to conventional measures of NS disease activity including proteinuria, hypercholesterolemia, and hypoalbuminemia. The overall disease activity model was well correlated with ETP (R² = 0.38). The relationship with disease activity was confirmed in the second cohort. These models further revealed that ETP is related to disease activity in a manner dependent on remission status.

CONCLUSION

Consistent with our previously reported animal model observations, we found that the combination of proteinuria, hypercholesterolemia, and hypoalbuminemia correlated with ETP-defined hypercoagulopathy. Hypercoagulopathy improved significantly with partial or complete NS remission. These data are expected to inform studies designed to stratify thrombotic risk for patients with NS.

Prediction models for recurrence and bleeding in patients with venous thromboembolism: A systematic review and critical appraisal

INTRODUCTION

Prediction models for recurrence and bleeding are infrequently used when deciding on anticoagulant treatment duration after venous thromboembolism (VTE) due to concerns about performance and validity. Our aim was to critically appraise these models by systematically summarizing data from derivation and validation studies.

MATERIALS AND METHODS

MEDLINE and CENTRAL were searched until November 15th, 2019. Studies on prediction models for recurrence or bleeding after at least 3 months of anticoagulation in adult patients with VTE were included. The PROBAST, ROBINS-I and RoB2 tools were used to assess risk of bias and applicability.

RESULTS

Selection yielded 18 studies evaluating 8 models for recurrence (7 on development; 9 on validation; 1 update). Generally, models for recurrent VTE appeared to perform poorly to moderately in external validation studies (C-statistics 0.39-0.66, one 0.83). However, impact studies show that HERDOO2 and Vienna prediction model may identify patients with unprovoked VTE at low recurrence risk. Sixteen studies evaluating 14 models for anticoagulation-related bleeding were identified (7 on development; 9 on validation). Although some models seemed promising in development studies, their predictive performance was poor to moderate in external validation (C-statistics 0.52-0.71). All but 3 studies were considered at high risk of bias, mainly due to limitations in the statistical analysis.

CONCLUSIONS

Prognostic models for recurrence and anticoagulation-related bleeding risk often have important methodological limitations and insufficient predictive accuracy. These findings do not support their use in clinical practice to weigh risks of recurrence and bleeding when deciding on continuing anticoagulation after initial treatment of VTE.

Individualised Risk Assessments for Recurrent Venous Thromboembolism: New Frontiers in the Era of Direct Oral Anticoagulants

Venous thromboembolism (VTE) is a leading cause of morbidity and mortality and is associated with high recurrence rates. The introduction of direct oral anticoagulants (DOACs) in the 2010s has changed the landscape of VTE management. DOACs have become the preferred anticoagulant therapy for their ease of use, predictable pharmacokinetics, and improved safety profile. Increasingly, guidelines have recommended long term anticoagulation for some indications such as following first unprovoked major VTE, although an objective individualised risk assessment for VTE recurrence remains elusive. The balance of preventing VTE recurrence needs to be weighed against the not insignificant bleeding risk, which is cumulative with prolonged use. Hence, there is a need for an individualised, targeted approach for assessing the risk of VTE recurrence, especially in those patients in whom the balance between benefit and risk of long-term anticoagulation is not clear. Clinical factors alone do not provide the level of discrimination required on an individual level. Laboratory data from global coagulation assays and biomarkers may provide enhanced risk assessment ability and are an active area of research. A review of the prediction models and biomarkers for assessing VTE recurrence risk is provided, with an emphasis on contemporary developments in the era of DOACs and global coagulation assays.

Association Between D-Dimer Level and In-Hospital Death of Pulmonary Embolism Patients

To investigate whether D-dimer level could predict pulmonary embolism (PE) severity and in-hospital death, a total of 272 patients with PE were divided into a survival group (n = 249) and a death group (n = 23). Comparisons of patient characteristics between the 2 groups were performed using Mann-Whitney U test. Significant variables in univariate analysis were entered into multivariate logistic regression analysis. Receiver operating characteristic (ROC) curve analysis was performed to determine the predictive value of D-dimer level alone or together with the simplified Pulmonary Embolism Severity Index (sPESI) for in-hospital death. Results showed that patients in the death group were significantly more likely to have hypotension (P = 0.008), tachycardia (P = 0.000), elevated D-dimer level (P = 0.003), and a higher sPESI (P = 0.002) than those in the survival group. Multivariable logistic regression analysis showed that D-dimer level was an independent predictor of in-hospital death (OR = 1.07; 95% CI, 1.003-1.143; P = 0.041). ROC curve analysis showed that when D-dimer level was 3.175 ng/ml, predicted death sensitivity and specificity were 0.913 and 0.357, respectively; and when combined with sPESI, specificity (0.838) and area under the curve (0.740) were increased. Thus, D-dimer level is associated with in-hospital death due to PE; and the combination with sPESI can improve the prediction level.

Biological variation data and analytical specification goal estimates of the thrombin generation assay with and without thrombomodulin in healthy individuals

BACKGROUND

Evaluation of an individual's thrombin-generating capacity enables a global assessment of the coagulation cascade and is therefore thought to better reflect the clotting function of blood. However, the lack of standardization still hampers the use in routine clinical practice.

METHODS

Nineteen healthy subjects were sampled once a week for 5 consecutive weeks. Thrombin generation assay (TGA) was performed in duplicate by calibrated automated thrombogram (CAT) on platelet poor plasma with and without thrombomodulin. After exclusion of outliers, a nested analysis of variance (ANOVA) was performed to evaluate the biological variability (BV) results. Analytical variation (CV_A ), within-individual variation (CV_I ), between-individual variation (CV_G ), index of individuality (II), and reference change value (RCV) were calculated.

RESULTS

All parameters taken together, the CV_A, CV_I , and CV_G without TM, ranged from 2.8% to 6.5%, from 4.1% to 13.3% and from 10.4% to 28.4%, respectively. For TG with TM, CV_I and CV_G were higher and ranged from 5.0% to 18.1% and from 14.9% to 35.3%, respectively. For endogenous thrombin potential (ETP), a CV_I of 4.1% and CV_G of 10.4% were obtained without addition of thrombomodulin (TM). With addition of TM, both CV_I and CV_G were higher: 14.0% and 34.8%, respectively. The II was low and the RCV ranged from 17.2% to 50.4%.

CONCLUSION

CAT parameters are highly individualized and population-based reference values could be called into question. The assessment of BV and RCV for thrombin generation assays could optimize interpretation of serial patient results and guide setting of analytical specification goals.

Diagnostic Accuracy in Acute Venous Thromboembolism: Comparing D-Dimer, Thrombin Generation, Overall Hemostatic Potential, and Fibrin Monomers

Introduction  For acute venous thromboembolism (VTE), a biomarker with higher specificity than D-dimer would be of great clinical use. Thrombin generation and overall hemostatic potential (OHP) reflect the hemostatic balance by globally assessing multiple coagulation factors and inhibitors. These tests discriminate between healthy controls and patients with a prothrombotic tendency but have yet to be established as clinical biomarkers of VTE.

Objective  This study compares endogenous thrombin potential (ETP) and OHP to D-dimer and fibrin monomers (FM) in outpatients with suspected VTE.

Methods  A cross-sectional diagnostic study where 954 patients with suspected pulmonary embolism or deep venous thrombosis were recruited consecutively from the medical emergency department at Karolinska University Hospital. D-dimer, FM, OHP, and ETP were analyzed in a subpopulation of 60 patients with VTE and 98 matched controls without VTE. VTE was verified either by ultrasonography or computed tomography and clinical data were collected from medical records.

Results  Compared with healthy controls, both VTE and non-VTE patients displayed prothrombotic profiles in OHP and ETP. D-dimer, FM, ETP area under the curve (AUC), and ETP T _lag were significantly different between patients with VTE and non-VTE. The largest receiver-operating characteristic AUCs for discrimination between VTE and non-VTE, were found in D-dimer with 0.94, FM 0.77, and ETP AUC 0.65. No useful cutoff could be identified for the ETP or the OHP assay.

Conclusion  Compared with D-dimer, neither ETP nor OHP were clinically viable biomarkers of acute venous thrombosis. The data indicated that a large portion of the emergency patients with suspected VTE were in a prothrombotic state.

Nephrotic syndrome-associated hypercoagulopathy is alleviated by both pioglitazone and glucocorticoid which target two different nuclear receptors

BACKGROUND

Thrombosis is a potentially life-threatening nephrotic syndrome (NS) complication. We have previously demonstrated that hypercoagulopathy is proportional to NS severity in rat models and that pioglitazone (Pio) reduces proteinuria both independently and in combination with methylprednisolone (MP), a glucocorticoid (GC). However, the effect of these treatments on NS-associated hypercoagulopathy remains unknown. We thus sought to determine the ability of Pio and GC to alleviate NS-associated hypercoagulopathy.

METHODS

Puromycin aminonucleoside-induced rat NS was treated with sham, Low- or High-dose MP, Pio, or combination (Pio + Low-MP) and plasma was collected at day 11. Plasma samples were collected from children with steroid-sensitive NS (SSNS) and steroid-resistant NS (SRNS) upon presentation and after 7 weeks of GC therapy. Plasma endogenous thrombin potential (ETP), antithrombin (AT) activity, and albumin (Alb) were measured using thrombin generation, amidolytic, and colorimetric assays, respectively.

RESULTS

In a rat model of NS, both High-MP and Pio improved proteinuria and corrected hypoalbuminemia, ETP and AT activity (p < .05). Proteinuria (p = .005) and hypoalbuminemia (p < .001) were correlated with ETP. In childhood NS, while ETP was not different at presentation, GC therapy improved proteinuria, hypoalbuminemia, and ETP in children with SSNS (p < .001) but not SRNS (p = .330).

CONCLUSIONS

Both Pio and GC diminish proteinuria and significantly alleviate hypercoagulopathy. Both Pio and MP improved hypercoagulopathy in rats, and successful GC therapy (SSNS) also improved hypercoagulopathy in childhood NS. These data suggest that even a partial reduction in proteinuria may reduce NS-associated thrombotic risk.

Usefulness of Thrombin Generation

Thrombin generation (TG) is a global coagulation procedure meant to continuously monitor thrombin formation and decay upon exposure of platelet-poor plasma to exogenous triggers such as tissue factor, phospholipids, and calcium chloride. The procedure can also be performed in platelet-rich plasma by omitting exogenous phospholipids. TG is thought to mimic more than other coagulation procedures the process that occurs in vivo. Over the years, TG has been used to investigate coagulation mechanisms, which were not completely understood, or to investigate hyper- or hypocoagulability in clinical conditions known to be at increased risk of thrombosis or hemorrhage, respectively. More recently, TG has been employed as a laboratory tool to assess the risk of recurrent venous thromboembolism or to assess the risk of arterial thromboembolism in specific clinical settings or in the general population. The article reviews the value and limitations of TG.

Investigation of patients with unclassified bleeding disorder and abnormal thrombin generation for physiological coagulation inhibitors reveals multiple abnormalities and a subset of patients with increased tissue factor pathway inhibitor activity

INTRODUCTION

We have routinely used thrombin generation to investigate patients with unclassified bleeding disorder (UBD).

AIMS

To investigate haemostatic abnormalities in patients with UBD that had abnormal thrombin generation on at least one occasion.

METHODS

Investigation of 13 known UBD patients with thrombin generation and detailed haemostatic testing was undertaken including TFPI assays but also thrombomodulin and fibrinogen-γ.

RESULTS

12 females and 1 male were included. No patient had a platelet function disorder or coagulation factor deficiency that explained the bleeding phenotype, though 2 patients had factor deficiencies; a factor X of 0.41 IU/mL and a factor XI of 0.51 IU/mL. ThromboGenomics revealed variants for these factors but no other abnormalities. Patients were included who previously had either prolonged lag time or decreased endogenous thrombin potential (ETP) via high dose tissue factor (5 pmol/L) or low dose tissue factor (1.5 pmol/L) with corn trypsin inhibitor (CTI). Tissue factor pathway inhibitor (TFPI) activity was significantly increased (P < .001; increased in 8 patients) compared with controls and abnormalities in soluble thrombomodulin (2 patients), fibrinogen-γ (1 patient) and tPA (4 patients for each) were seen. Total and free TFPI levels were not increased. Mixing studies of patient plasma with 50:50 normal plasma for thrombin generation via low dose tissue factor failed to correct the ETP consistent with ongoing inhibition. Addition of an anti-TFPI antibody partially corrected thrombin generation to normal levels. TFPI sequencing was unremarkable.

CONCLUSION

TFPI activity may be increased in a subset of UBD patients. Further research studies are warranted in UBD patients for coagulation inhibitor abnormalities.

D-Dimer Predicts Disease Severity but Not Long-Term Prognosis in Acute Pulmonary Embolism

D-dimer might be correlated with prognosis in pulmonary embolism (PE). The predictive value of plasma D-dimer for disease severity and survival was investigated in the lowest and highest D-dimer quartile among 200 patients with PE. Patients with high D-dimers were significantly more often hypotensive (P = .001), tachycardic (P = .016), or hypoxemic (P = .001). Pulmonary arterial obstruction index (PAOI) values were significantly higher in the high D-dimer quartile (P < .001). Elevated troponin I (TNI) levels (P < .001), simplified PE severity indices ≥1 (P < .001), right-to-left ventricular (RV/LV) diameter ratios ≥1 (P < .001), and thrombolysis (P = .001) were more frequent in the high D-dimer quartile. D-dimer was associated with RV/LV ratios ≥1 (P = .021), elevated PAOI (P < .001) or TNI levels (P < .001), hypotension (P < .001), tachycardia (P = .003), and hypoxemia (P < .001), but not with long-term all-cause mortality. D-dimer predicts disease severity but not long-term prognosis in acute PE, possibly due to a more aggressive treatment strategy in severely affected patients.

Mode of Delivery Does Not Influence Postpartum Hypercoagulability Measured by Thrombin Generation or Thromboelastometry

Introduction  Venous thromboembolism (VTE) is a significant cause of maternal mortality with the greatest risk postpartum. Mode of delivery influences VTE risk, with emergency caesarean section (CS) associated with the highest risk (CS). Thromboprophylaxis is recommended for selected women to reduce the risk of VTE.

We aimed to investigate the impact of mode of delivery and thromboprophylaxis on hypercoagulability as measured by thromboelastometry (TEM) and thrombin generation (TG) in women at high VTE risk.

Materials and Methods  Blood was collected from 99 pregnant women with VTE risk factors at up to five time points from pre- (T1) and post (T2)-delivery to 6 weeks postpartum (T5). Multiple linear regression was utilised to compare TG and TEM between those with vaginal delivery (VD) and CS at each time point. Paired sample t -test with post hoc Bonferroni correction was utilised to compare laboratory markers over time.

Results  Women in both groups had a median of three postpartum VTE risk factors, with higher body mass index and parity post-VD. In both the groups, TG and TEM parameters suggested hypercoagulability at T2 compared with T1, with resolution at T5. There were minimal differences between groups, apart from T2 with shorter clot formation time and higher maximum clot firmness in the VD group.

Conclusion  TG and TEM illustrate hypercoagulability associated with pregnancy and delivery. The pattern of postpartum hypercoagulability seen in women with VTE risk factors was similar irrespective of mode of delivery. Further research is required to establish the effect of labour on TG/TEM in the absence of low molecular weight heparin use.

Different strategies for pharmacological thromboprophylaxis for lower-limb immobilisation after injury: systematic review and economic evaluation

BACKGROUND

Thromboprophylaxis can reduce the risk of venous thromboembolism (VTE) during lower-limb immobilisation, but it is unclear whether or not this translates into meaningful health benefit, justifies the risk of bleeding or is cost-effective. Risk assessment models (RAMs) could select higher-risk individuals for thromboprophylaxis.

OBJECTIVES

To determine the clinical effectiveness and cost-effectiveness of different strategies for providing thromboprophylaxis to people with lower-limb immobilisation caused by injury and to identify priorities for future research.

DATA SOURCES

Ten electronic databases and research registers (MEDLINE, EMBASE, Cochrane Database of Systematic Reviews, Database of Abstracts of Review of Effects, the Cochrane Central Register of Controlled Trials, Health Technology Assessment database, NHS Economic Evaluation Database, Science Citation Index Expanded, ClinicalTrials.gov and the International Clinical Trials Registry Platform) were searched from inception to May 2017, and this was supplemented by hand-searching reference lists and contacting experts in the field.

REVIEW METHODS

Systematic reviews were undertaken to determine the effectiveness of pharmacological thromboprophylaxis in lower-limb immobilisation and to identify any study of risk factors or RAMs for VTE in lower-limb immobilisation. Study quality was assessed using appropriate tools. A network meta-analysis was undertaken for each outcome in the effectiveness review and the results of risk-prediction studies were presented descriptively. A modified Delphi survey was undertaken to identify risk predictors supported by expert consensus. Decision-analytic modelling was used to estimate the incremental cost per quality-adjusted life-year (QALY) gained of different thromboprophylaxis strategies from the perspectives of the NHS and Personal Social Services.

RESULTS

Data from 6857 participants across 13 trials were included in the meta-analysis. Thromboprophylaxis with low-molecular-weight heparin reduced the risk of any VTE [odds ratio (OR) 0.52, 95% credible interval (CrI) 0.37 to 0.71], clinically detected deep-vein thrombosis (DVT) (OR 0.40, 95% CrI 0.12 to 0.99) and pulmonary embolism (PE) (OR 0.17, 95% CrI 0.01 to 0.88). Thromboprophylaxis with fondaparinux (Arixtra®, Aspen Pharma Trading Ltd, Dublin, Ireland) reduced the risk of any VTE (OR 0.13, 95% CrI 0.05 to 0.30) and clinically detected DVT (OR 0.10, 95% CrI 0.01 to 0.94), but the effect on PE was inconclusive (OR 0.47, 95% CrI 0.01 to 9.54). Estimates of the risk of major bleeding with thromboprophylaxis were inconclusive owing to the small numbers of events. Fifteen studies of risk factors were identified, but only age (ORs 1.05 to 3.48), and injury type were consistently associated with VTE. Six studies of RAMs were identified, but only two reported prognostic accuracy data for VTE, based on small numbers of patients. Expert consensus was achieved for 13 risk predictors in lower-limb immobilisation due to injury. Modelling showed that thromboprophylaxis for all is effective (0.015 QALY gain, 95% CrI 0.004 to 0.029 QALYs) with a cost-effectiveness of £13,524 per QALY, compared with thromboprophylaxis for none. If risk-based strategies are included, it is potentially more cost-effective to limit thromboprophylaxis to patients with a Leiden thrombosis risk in plaster (cast) [L-TRiP(cast)] score of ≥ 9 (£20,000 per QALY threshold) or ≥ 8 (£30,000 per QALY threshold). An optimal threshold on the L-TRiP(cast) receiver operating characteristic curve would have sensitivity of 84-89% and specificity of 46-55%.

LIMITATIONS

Estimates of RAM prognostic accuracy are based on weak evidence. People at risk of bleeding were excluded from trials and, by implication, from modelling.

CONCLUSIONS

Thromboprophylaxis for lower-limb immobilisation due to injury is clinically effective and cost-effective compared with no thromboprophylaxis. Risk-based thromboprophylaxis is potentially optimal but the prognostic accuracy of existing RAMs is uncertain.

FUTURE WORK

Research is required to determine whether or not an appropriate RAM can accurately select higher-risk patients for thromboprophylaxis.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42017058688.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Rivaroxaban Effects Illustrate the Underestimated Importance of Activated Platelets in Thrombin Generation Assessed by Calibrated Automated Thrombography

Background: The direct oral anticoagulant rivaroxaban inhibiting specifically activated factor X (FXa) causes delayed thrombin generation (TG) as measured by calibrated automated thrombography (CAT). The implications of these changes for assessing bleeding or residual prothrombotic risks of patients are unclear in the absence of a better understanding of the underlying mechanism. Methods: We compared platelet rich plasma (PRP) without or with prior collagen-induced platelet aggregation (agPRP) in the CAT assay to better characterize TG in the presence of rivaroxaban. Results: In the presence of rivaroxaban, TG curves in agPRP showed a distinct profile with a rapidly ascending phase followed with a protracted phase. Inhibition of tissue factor pathway inhibitor amplified the first phase of the curve which was also modulated by procoagulant phospholipids. Inhibition of FXIIa-dependent FXI activation revealed that aggregated platelets influenced the first phase by a combination of extrinsic and intrinsic coagulation pathway initiations. Thrombin-dependent amplification of TG (even prior collagen activation) was responsible for the second phase of the TG curve. Conclusions: AgPRP fully includes platelet ability to support TG and reveal distinct TG phases in the presence of direct FXa inhibitors highlighting its potential use in an anticoagulated setting.

LIM-only protein FHL2 attenuates vascular tissue factor activity, inhibits thrombus formation in mice and FHL2 genetic variation associates with human venous thrombosis

Bleeding disorders and thrombotic complications are major causes of morbidity and mortality with many cases being unexplained. Thrombus formation involves aberrant expression and activation of tissue factor (TF) in vascular endothelial and smooth muscle cells. Here, we sought to identify factors that modulate TF gene expression and activity in these vascular cells. The LIM-only protein FHL2 is a scaffolding protein that modulates signal transduction pathways with crucial functions in endothelial and smooth muscle cells. However, the role of FHL2 in TF regulation and thrombosis remains unexplored. Using a murine model of venous thrombosis in mesenteric vessels, we demonstrated that FHL2 deficiency results in exacerbated thrombus formation. Gain- and loss-of-function experiments revealed that FHL2 represses TF expression in endothelial and smooth muscle cells through inhibition of the transcription factors nuclear factor κB and activating protein-1. Furthermore, we observed that FHL2 interacts with the cytoplasmic tail of TF. In line with our in vivo observations, FHL2 decreases TF activity in endothelial and smooth muscle cells whereas FHL2 knockdown or deficiency results in enhanced TF activity. Finally, the FHL2 single nucleotide polymorphism rs4851770 was associated with the risk of venous thrombosis in a large population of venous thrombosis cases and control subjects from 12 studies (INVENT consortium). Altogether, our results highlight functional involvement of FHL2 in TF-mediated coagulation and identify FHL2 as a novel gene associated with venous thrombosis in humans.

[Contemporary approaches to determine the duration of anticoagulant therapy for venous thromboembolism]

The review is devoted to the issue of optimal duration of anticoagulant therapy for venous thromboembolic complications (VTEC) using oral anticoagulants (OAC). These drugs are characterized by higher safety in comparison with vitamin K antagonists and make it possible to increase the duration of treatment for not only spontaneous thrombosis (with high risk of recurrence), but also thrombosis provoked by minor persistent and transient risk factors of VTEC. Efficacy and safety of prolonged treatment of VTEC using OAC was analyzed. Different classifications of primary thrombotic episode depending on risk of subsequent recurrence are presented. Moreover, scales for individual assessment of risk of recurrent thrombosis after anticoagulant therapy cancellation and risk of bleeding in case of continued treatment are given. Outcomes of long-term administration of rivaroxaban for VTEC are analyzed. It was concluded that OAC are safe for prolonged management of primary thrombotic episode. However, overall duration of treatment should be determined considering individual balance of benefits and risks.

Rosuvastatin use reduces thrombin generation potential in patients with venous thromboembolism: a randomized controlled trial

Essentials The role of statins in hemostasis and venous thromboembolism (VTE) prophylaxis is not clear. This trial assessed whether rosuvastatin use affects thrombin generation in patients with VTE. Endogenous thrombin potential and peak were decreased by 10% and 5% with rosuvastatin therapy. These results provide basis for trials on the efficacy of statins in reducing recurrent VTE risk. SUMMARY: Background Statin therapy could form an alternative prophylactic treatment for venous thromboembolism (VTE) if statins are proven to downregulate hemostasis and prevent recurrent VTE, without increasing bleeding risk. Objectives The STAtins Reduce Thrombophilia (START) trial investigated whether statin affects coagulation in patients with prior VTE. Patients/methods After anticoagulation withdrawal, patients were randomized to rosuvastatin 20 mg day-1 for 4 weeks or no intervention. Plasma samples taken at baseline and at the end of the study were analyzed employing thrombin generation assay. Results and conclusions The study comprised 126 rosuvastatin users and 119 non-users. Mean age was 58 years, 61% were men, 49% had unprovoked VTE and 75% had cardiovascular (CV) risk factors. Endogenous thrombin potential (ETP) increased from baseline to end of study in non-statin users (mean 97.22 nm*min; 95% CI, 40.92-153.53) and decreased in rosuvastatin users (mean -24.94 nm*min; 95% CI, -71.81 to 21.93). The mean difference in ETP change between treatments was -120.24 nm*min (95% CI, -192.97 to -47.51), yielding a 10.4% ETP reduction by rosuvastatin. The thrombin peak increased in both non-statin (mean 20.69 nm; 95% CI, 9.80-31.58) and rosuvastatin users (mean 8.41 nm; 95% CI -0.86 to 17.69). The mean difference in peak change between treatments was -11.88 nm (95% CI, -26.11 to 2.35), yielding a 5% peak reduction by rosuvastatin. Other thrombin generation parameters did not change substantially. The reduction in ETP and peak by rosuvastatin was more pronounced in the subgroups of participants with CV risk factors and with unprovoked VTE. We conclude that rosuvastatin reduces thrombin generation potential in patients who had VTE.

Targeted sequencing to identify novel genetic risk factors for deep vein thrombosis: a study of 734 genes

Essentials Deep vein thrombosis (DVT) has a large unknown genetic component. We sequenced coding areas of 734 hemostasis-related genes in 899 DVT patients and 599 controls. Variants in F5, FGA-FGG, CYP4V2-KLKB1-F11, and ABO were associated with DVT risk. Associations in KLKB1 and F5 suggest a more complex genetic architecture than previously thought. SUMMARY: Background Although several genetic risk factors for deep vein thrombosis (DVT) are known, almost all related to hemostasis, a large genetic component remains unexplained. Objectives To identify novel genetic determinants by using targeted DNA sequencing. Patients/Methods We included 899 DVT patients and 599 controls from three case-control studies (DVT-Milan, Multiple Environmental and Genetic Assessment of risk factors for venous thrombosis [MEGA], and the Thrombophilia, Hypercoagulability and Environmental Risks in Venous Thromboembolism [THE-VTE] study) for sequencing of the coding regions of 734 genes involved in hemostasis or related pathways. We performed single-variant association tests for common variants (minor allele frequency [MAF] ≥ 1%) and gene-based tests for rare variants (MAF ≤ 1%), accounting for multiple testing by use of the false discovery rate (FDR). Results Sixty-two of 3617 common variants were associated with DVT risk (FDR < 0.10). Most of these mapped to F5,ABO,FGA-FGG, and CYP4V2-KLKB1-F11. The lead variant at F5 was rs6672595 (odds ratio [OR] 1.58, 95% confidence interval [CI] 1.29-1.92), in moderate linkage with the known variant rs4524. Reciprocal conditional analyses suggested that intronic variation might drive this association. We also observed a secondary association at the F11 region: missense KLKB1 variant rs3733402 remained associated conditional on known variants rs2039614 and rs2289252 (OR 1.36, 95% CI 1.10-1.69). Two novel variant associations were observed, in CBS and MASP1, but these were not replicated in the meta-analysis data from the International Network against Thrombosis (INVENT) consortium. There was no support for a burden of rare variants contributing to DVT risk (FDR > 0.2). Conclusions We confirmed associations between DVT and common variants in F5,ABO,FGA-FGG, and CYP4V2-KLKB1-F11, and observed secondary signals in F5 and CYP4V2-KLKB1-F11 that warrant replication and fine-mapping in larger studies.

Discovery of novel plasma biomarkers for future incident venous thromboembolism by untargeted synchronous precursor selection mass spectrometry proteomics

Essentials Discovery of predictive biomarkers of venous thromboembolism (VTE) may aid risk stratification. A case-control study where plasma was sampled before the occurrence of VTE was established. We generated untargeted plasma proteomic profiles of 200 individuals by use of mass spectrometry. Assessment of the biomarker potential of 501 proteins yielded 46 biomarker candidates.

ABSTRACT

Background Prophylactic anticoagulant treatment may substantially reduce the incidence of venous thromboembolism (VTE) but entails considerable risk of severe bleeding. Identification of individuals at high risk of VTE through the use of predictive biomarkers is desirable in order to achieve a favorable benefit-to-harm ratio. Objective We aimed to identify predictive protein biomarker candidates of VTE. Methods We performed a case-control study of 200 individuals that participated in the Tromsø Study, a population-based cohort, where blood samples were collected before the VTE events occurred. Untargeted tandem mass tag-synchronous precursor selection-mass spectrometry (TMT-SPS-MS3)-based proteomic profiling was used to study the plasma proteomes of each individual. Results Of the 501 proteins detected in a sufficient number of samples to allow multivariate analysis, 46 proteins were associated with VTE case-control status with P-values below the 0.05 significance threshold. The strongest predictive biomarker candidates, assessed by statistical significance, were transthyretin, vitamin K-dependent protein Z and protein/nucleic acid deglycase DJ-1. Conclusions Our untargeted approach of plasma proteome profiling revealed novel predictive biomarker candidates of VTE and confirmed previously reported candidates, thereby providing conceptual support for the validity of the study. A larger nested case-control study will be conducted to validate our findings.

Clinical bleeding and thrombin generation in admissions to critical care with prolonged prothrombin time: an exploratory study

BACKGROUND

Prolongation of prothrombin time (PT) is often recorded in critical illness, but has limited ability to predict risk of bleeding. This exploratory study was aimed at assessing a role for thrombin generation (TG) to predict bleeding.

STUDY DESIGN AND METHODS

TG was measured by calibrated automated thrombography in admissions to intensive care with prolonged PT. Bleeding events were recorded up to Day 5 after enrollment and correlated with results of PT ratio (PTR) and variables of TG.

RESULTS

A total of 306 patients were recruited. A total of 101 bleeding events developed in 46 patients during the period of observation. Many patients with prolonged PT had endogenous thrombin potential (ETP), which was within the normal range (120/251 patients, 47.8%) or even elevated (8%). Although some patients had a reduction in ETP or peak thrombin, these were present over a wide range of PTR. There was no suggestion by receiver operating characteristic analysis that variables of conventional TG were sensitive at predicting bleeding. No bleeding events were documented in patients defined as ETP high, despite elevated PTR.

CONCLUSION

Future studies need to explore a role for alternatives tests of coagulation in critical illness. Development of TG assays is required to positively identify more patients at increased bleeding risk or to exclude a larger number at low risk and how this relates to subgroups, such as patients with liver disease, and the need for prophylactic plasma transfusion.

Genome-Wide Association Study Identifies a Novel Genetic Risk Factor for Recurrent Venous Thrombosis

Background:

Genetic risk factors for a first venous thrombosis (VT) seem to have little effect on recurrence risk. Therefore, we aimed specifically to identify novel genetic determinants of recurrent VT. To date, genome-wide association studies are lacking.

Methods and Results:

We performed a genome-wide association scan in 1279 patients from the MEGA (Multiple Environmental and Genetic Assessment of risk factors for venous thrombosis) follow-up study; 832 patients who remained recurrence free during a median follow-up time of 6.1 years and 447 recurrent VT patients with a median time-to-recurrence of 2.6 years. We analyzed genotype probabilities of ≈8.6 million variants, imputed to the Genome of the Netherlands project reference panel, with a minor allele frequency ≥1% for an association with recurrent VT. One region exceeded genome-wide significance ( P ≤5×10 − 8 ), mapping to the well-known factor V Leiden locus. Conditional association analyses on factor V Leiden did not yield any secondary association signals. We also identified 52 suggestive association signals ( P <1×10 −5 ) at 17 additional loci. None of these loci were previously implicated in VT risk. Replication analyses for 17 lead variants were performed in 350 patients with recurrent VT and 1866 patients with a single VT event from the MEGA follow-up study, THE-VTE (Thrombophilia, Hypercoagulability and Environmental Risks in Venous Thromboembolism) study, and LETS (Leiden Thrombophilia Study). We observed an association with recurrence for an intergenic variant at 18q22.1 with an odds ratio of 1.7 (95% confidence interval, 1.2–2.6) per copy of the minor allele.

Conclusions:

We confirmed the association of factor V Leiden and identified a novel risk locus at 18q22.1 in the first large genetic study on recurrent VT.