Elevated factor XIa as a modulator of plasma fibrin clot properties in coronary artery disease.

INTRODUCTION: Patients with coronary artery disease (CAD) display a prothrombotic fibrin clot phenotype, involving low permeability and resistance to lysis. The determinants of this phenotype remain elusive. Circulating tissue factor (TF) and activated factor XI (FXIa) are linked to arterial thromboembolism. We investigated whether detectable active TF and FXIa influence fibrin clot properties in CAD. METHODS: In 118 CAD patients (median age 65 years, 78% men), we assessed Ks, an indicator of clot permeability, and clot lysis time (CLT) in plasma-based assays, along with the presence of active TF and FXIa. We also analysed proteins involved in clotting and thrombolysis, including fibrinogen, plasminogen activator inhibitor-1 (PAI-1) and thrombin activatable thrombolysis inhibitor (TAFI). During a median 106 month (interquartile range 95-119) follow-up, myocardial infarction (MI), stroke, systemic thromboembolism (SE) and cardiovascular (CV) death were recorded. RESULTS: Circulating TF and FXIa, detected in 20.3% and 39.8% of patients, respectively, were associated with low Ks and prolonged CLT. Solely FXIa remained an independent predictor of low Ks and high CLT on multivariable analysis. Additionally, fibrinogen and PAI-1 were associated with low Ks, while PAI-1 and TAFI-with prolonged CLT. During follow-up low Ks and prolonged CLT increased the risk of MI and the latter also a composite endpoint of MI, stroke/SE or CV death. CONCLUSIONS: To our knowledge, this study is the first to show that circulating FXIa is associated with prothrombotic fibrin clot properties in CAD, suggesting additional mechanisms through which FXIa inhibitors could act as novel antithrombotic agents in CAD.

Anti-FVIII antibodies in Black and White hemophilia A subjects: do F8 haplotypes play a role?

The most common complication in hemophilia A (HA) treatment, affecting 25% to 30% of patients with severe HA, is the development of alloimmune inhibitors that foreclose the ability of infused factor VIII (FVIII) to participate in coagulation. Inhibitors confer significant pathology on affected individuals and present major complexities in their management. Inhibitors are more common in African American patients, and it has been hypothesized that this is a consequence of haplotype (H)-treatment product mismatch. F8 haplotypes H1 to H5 are defined by nonsynonymous single-nucleotide polymorphisms encoding sequence variations at FVIII residues 1241, 2238, and 484. Haplotypes H2 to H5 are more prevalent in individuals with Black African ancestry, whereas 80% to 90% of the White population has the H1 haplotype. This study used an established multiplex fluorescence immunoassay to determine anti-FVIII antibody titers in plasma from 394 individuals with HA (188 Black, 206 White), measuring their binding to recombinant full-length H1 and H2 and B-domain-deleted (BDD) H1/H2, H3/H5, and H4 FVIII proteins. Inhibitor titers were determined using a chromogenic assay and linear B-cell epitopes characterized using peptide microarrays. FVIII-reactive antibodies were readily detected in most individuals with HA, with higher titers in those with a current inhibitor, as expected. Neither total nor inhibitory antibody titers correlated with F8 haplotype mismatches, and peptides with D1241E and M2238V polymorphisms did not comprise linear B-cell epitopes. Interestingly, compared with the full-length FVIII products, the BDD-FVIII proteins were markedly more reactive with plasma antibodies. The stronger immunoreactivity of BDD-FVIII suggests that B-domain removal might expose novel B-cell epitopes, perhaps through conformational rearrangements of FVIII domains.

Activated factor XI is associated with increased factor VIIa - Antithrombin complexes in stable coronary artery disease: Impact on cardiovascular outcomes.

BACKGROUND: Coronary artery disease (CAD) is associated with a prothrombotic tendency including increased factor (F) VIIa-antithrombin (FVIIa-AT) complexes, a measure of tissue factor (TF) exposure, and activated FXI (FXIa). We investigated whether increased FVIIa-AT complexes are associated with FXIa and active TF and if major adverse clinical outcomes are predicted by the complexes in CAD. METHODS: In 120 CAD patients, we assessed FVIIa-AT complex concentrations and the presence of circulating FXIa and active TF. Levels of 8-iso-prostaglandin F2α (8-iso-PGF2α), interleukin-6, high-sensitivity C reactive protein, prothrombin fragment 1 + 2, and free Tissue Factor Pathway Inhibitor were determined. Myocardial infarction (MI), ischemic stroke, systemic thromboembolism (SE), and cardiovascular (CV) death were recorded separately and as a composite endpoint, during follow-up. RESULTS: FVIIa-AT complexes were positively associated with current smoking and multivessel CAD. Elevated FVIIa-AT complexes characterized patients with circulating FXIa and/or active TF in association with increased plasma isoprostanes but not with thrombin generation or inflammatory markers. During a median follow-up of 106 months (interquartile range 95-119), high baseline levels of FVIIa-AT complexes predicted ischemic stroke/SE (HR 4.61 [95% CI 1.48-18.42]) and a composite endpoint of MI, stroke/SE, and CV death (HR 7.47 [95% CI 2.81-19.87]). CONCLUSIONS: This study is the first to show that high FVIIa-AT complexes characterize advanced CAD patients with detectable FXIa and active TF, which is, in part, driven by oxidative stress. High FVIIa-AT complexes were associated with the risk of ischemic stroke/SE during long-term follow-up, highlighting the need for effective antithrombotic agents in CAD.

Active factor XI is associated with the risk of cardiovascular events in stable coronary artery disease patients.

BACKGROUND AND AIMS: Tissue factor (TF) and activated factor XI (FXIa) have been associated with acute coronary syndrome, ischemic stroke and venous thromboembolism. Their predictive value in stable coronary artery disease (CAD) is unclear. We investigated whether active TF and FXIa were associated with clinical outcomes in CAD patients in long-term observation. METHODS: In 124 stable patients with multivessel CAD, we assessed the presence of circulating, active TF and FXIa by measuring a response of thrombin generation to respective inhibitory antibodies. We recorded the composite endpoint of myocardial infarction (MI), stroke, systemic thromboembolism and cardiovascular death during follow-up (median 106 months, interquartile range 95-119). RESULTS: Circulating FXIa and active TF were detected in 40% and 20.8% of the 120 patients (aged 65.0 [57.0-70.3] years, men, 78.3%), who completed follow-up. The composite endpoint occurred more frequently in patients with detectable active TF and FXIa present at baseline (hazard ratio [HR] 4.02, 95% confidence interval [CI] 2.26-7.17, p < 0.001 and HR 6.21, 95% CI 3.40-11.40, p < 0.001, respectively). On multivariate analysis FXIa, but not active TF, was an independent predictor of the composite endpoint, as well as MI, stroke/systemic thromboembolism, and cardiovascular death, when analyzed separately. CONCLUSIONS: To our knowledge, this study is the first to show that circulating FXIa predicts arterial thromboembolic events in advanced CAD, supporting a growing interest in FXIa inhibitors as novel antithrombotic agents.

Active FXI Can Independently Predict Ischemic Stroke in Anticoagulated Atrial Fibrillation Patients: A Cohort Study.

BACKGROUND: Atrial fibrillation (AF) is associated with a prothrombotic state. Presence of active tissue factor (TF), activated factor IX (FIXa) and FXIa in circulating blood contributes to thrombosis. We investigated a prognostic value of these factors in AF patients. METHODS: In this cohort study, 284 AF patients (aged 63.3 ± 8.8 years) treated with oral anticoagulants were enrolled. Plasma levels of active coagulation factors were evaluated using thrombin generation assay. Concentrations of fibrinogen, D-dimer, interleukin-6 (IL-6), and endothelial damage markers, including von Willebrand factor (VWF) and soluble (s)E-selectin, were also measured. Ischemic stroke and cardiovascular death, analyzed separately or as a composite endpoint, were recorded during a mean follow-up of 47 months. RESULTS: Cerebrovascular events were observed in 20 patients (1.8%/year) who had at baseline higher fibrinogen, D-dimer, and VWF levels. Active TF and FXIa at enrollment were detectable in 12 (60%) and 15 (75%) patients who experienced ischemic stroke during follow-up. The composite endpoint observed in 23 patients (2.1%/year) was associated with increased concentrations of the above laboratory variables, along with 26% higher IL-6 levels. sE-selectin did not differ between the studied groups. On multivariable regression analysis, advanced age, anticoagulation discontinuation, and detectable FXIa, but not active TF, independently predicted the composite endpoint. No associations of FIXa with the study endpoints were observed. CONCLUSION: FXIa present in circulating blood is associated with increased risk of ischemic stroke and cardiovascular death in anticoagulated AF patients during long-term follow-up. FXIa inhibition could be useful in cardiovascular prevention in AF beyond the current oral anticoagulation.

Exploring the utility of a novel point-of-care whole blood thrombin generation assay following trauma: A pilot study.

INTRODUCTION: Plasma thrombin generation kinetics as measured by the calibrated automated thrombogram (CAT) assay is a predictor of symptomatic venous thromboembolism after trauma. We hypothesized that data from a new prototype assay for measurement of thrombin generation kinetics in fresh whole blood (near patient testing of thrombin generation), will correlate with the standard CAT assay in the same patients, making it a potential tool in the future care of trauma patients. METHODS: Patients were enrolled from June 2018 to February 2020. Within 12 hours of injury, blood samples were collected simultaneously for both assays. Variables compared and correlated between assays were lag time, peak height, time to peak, and endogenous thrombin potential. Data are presented as median with interquartile range (IQR). Spearman and Pearson correlations were estimated and tested between both assays; a P value of <0.05 was considered to be significant. RESULTS: A total of 64 trauma patients had samples analyzed: injury severity score = 17 (IQR), 10-26], hospital length of stay = 7.5 (IQR), 2-18) days, age = 52 (IQR, 35-63) years, 71.9% male, and 42.2% of patients received a transfusion within 24 hours of injury. Thrombin generation parameters between plasma and whole blood were compared and found that all parameters of the two assays correlate in trauma patients. CONCLUSION: In this pilot study, we have found that a novel point-of-care whole blood thrombin generation assay yields results with modest but statistically significant correlations to those of a standard plasma thrombin generation assay. This finding supports studying this device in a larger, adequately powered study.

Whole Blood Thrombin Generation in Severely Injured Patients Requiring Massive Transfusion.

BACKGROUND: Despite the prevalence of hypocoagulability after injury, the majority of trauma patients paradoxically present with elevated thrombin generation (TG). Although several studies have examined plasma TG post injury, this has not been assessed in whole blood. We hypothesize that whole blood TG is lower in hypocoagulopathy, and TG effectively predicts massive transfusion (MT). STUDY DESIGN: Blood was collected from trauma activation patients at an urban Level I trauma center. Whole blood TG was performed with a prototype point-of-care device. Whole blood TG values in healthy volunteers were compared with trauma patients, and TG values were examined in trauma patients with shock and MT requirement. RESULTS: Overall, 118 patients were included. Compared with healthy volunteers, trauma patients overall presented with more robust TG; however, those arriving in shock (n = 23) had a depressed TG, with significantly lower peak thrombin (88.3 vs 133.0 nM; p = 0.01) and slower maximum rate of TG (27.4 vs 48.3 nM/min; p = 0.04). Patients who required MT (n = 26) had significantly decreased TG, with a longer lag time (median 4.8 vs 3.9 minutes, p = 0.04), decreased peak thrombin (median 71.4 vs 124.2 nM; p = 0.0003), and lower maximum rate of TG (median 15.8 vs 39.4 nM/min; p = 0.01). Area under the receiver operating characteristics (AUROC) analysis revealed lag time (AUROC 0.6), peak thrombin (AUROC 0.7), and maximum rate of TG (AUROC 0.7) predict early MT. CONCLUSIONS: These data challenge the prevailing bias that all trauma patients present with elevated TG and highlight that deficient thrombin contributes to the hypocoagulopathic phenotype of trauma-induced coagulopathy. In addition, whole blood TG predicts MT, suggesting point-of-care whole blood TG can be a useful tool for diagnostic and therapeutic strategies in trauma.

Delayed Thrombin Generation Is Associated with Minor Bleedings in Venous Thromboembolism Patients on Rivaroxaban: Usefulness of Calibrated Automated Thrombography.

Bleeding is the most feared and difficult to predict adverse event of anticoagulation. We sought to investigate whether calibrated automated thrombography (CAT) parameters are associated with minor bleeding (MB) in anticoagulated patients following venous thromboembolism (VTE). Enrolled were 132 patients on rivaroxaban, 145 on vitamin K antagonists (VKA) and 31 controls who stopped anticoagulation. Prior to the next dose of the anticoagulant, we measured CAT parameters, along with rivaroxaban concentration and INR. During a median follow-up of 10 months, we recorded minor and major bleedings. On rivaroxaban, 27 (20.5%) patients with MB had longer time to start thrombin generation, lower peak thrombin generation and lower endogenous thrombin potential compared with subjects without MB (all p < 0.001). All CAT parameters, except for peak thrombin generation (p = 0.049), were similar in VKA patients with (n = 25, 17.2%) vs. without MBs. By logistic regression, time to start thrombin generation (p = 0.007) and unprovoked VTE (p = 0.041) independently predicted MBs on rivaroxaban. Major bleedings were more frequent in patients with MBs (17.3% vs. 1.8%, p < 0.001). Abnormal CAT parameters characterize VTE patients prone to MBs on rivaroxaban, but not on VKA. Time to start thrombin generation measured about 24 h since the last rivaroxaban dose might help predict MBs.

Dense and dangerous: The tissue plasminogen activator-resistant fibrinolysis shutdown phenotype is due to abnormal fibrin polymerization.

BACKGROUND: Both hyperfibrinolysis and fibrinolysis shutdown can occur after severe trauma. The subgroup of trauma patients with fibrinolysis shutdown resistant to tissue plasminogen activator (t-PA)-mediated fibrinolysis have increased mortality. Fibrin polymerization and structure may influence fibrinolysis subgroups in trauma, but fibrin architecture has not been characterized in acutely injured subjects. We hypothesized that fibrin polymerization measured in situ will correlate with fibrinolysis subgroups. METHODS: Blood samples were collected from trauma patients and noninjured controls. We selected samples across a range of fibrinolysis phenotypes (shutdown, physiologic, hyperfibrinolysis) and t-PA sensitivities (sensitive, physiologic, resistant) determined by thrombelastography. Plasma clots were created in situ with fluorescent fibrinogen and imaged using confocal microscopy for analysis of clot architecture in three dimensions. For each clot, we quantified the fiber resolvability, a metric of fiber distinctness or clarity, by mapping the variance of fluorescence intensity relative to background fluorescence. We also determined clot porosity by measuring the size and distribution of the gaps between fibrin fibers in three-dimensional space. We compared these measures across fibrinolysis subgroups. RESULTS: Fiber resolvability was significantly lower in all trauma subgroups compared with controls (n = 35 and 5, respectively; p < 0.05). We observed markedly different patterns of fibrin architecture among trauma patients stratified by fibrinolysis subgroup. Subjects with t-PA-resistant fibrinolysis shutdown exhibited abnormal, densely packed fibrin clots nearly devoid of pores. Individuals with t-PA-hypersensitive fibrinolysis shutdown had highly irregular clots with pores as large as 2500 µm to 20,000 µm, versus 78 µm to 1250 µm in noninjured controls. CONCLUSION: Fiber resolvability was significantly lower in trauma patients than controls, and subgroups of fibrinolysis differ in the porosity of the fibrin clot structure. The dense fibrin network in the t-PA-resistant group may prevent access to plasmin, suggesting a mechanism for thrombotic morbidity after injury.

Whole blood thrombin generation is distinct from plasma thrombin generation in healthy volunteers and after severe injury.

BACKGROUND: Plasma thrombin generation has been used to characterize trauma-induced coagulopathy, but description of whole blood thrombin generation is lacking. This study aimed to evaluate plasma and whole blood thrombin generation in healthy volunteers and trauma patients. We hypothesized that (1) plasma and whole blood thrombin generation are distinct, (2) whole blood thrombin generation is more pronounced in trauma patients than in healthy volunteers, and (3) thrombin generation correlates with clinical coagulation assays. METHODS: Blood was collected from healthy volunteers and trauma patients at a single, level-1 trauma center. Whole blood thrombin generation was assessed with a prototype point-of-care whole blood thrombin generation device, and plasma thrombin generation was measured with a calibrated automated thrombogram analogue. Plasma and whole blood thrombin generation were compared and correlated with international normalized ratio and thrombelastography. RESULTS: Overall, 10 healthy volunteers (average age 30, 50% men) were included and 58 trauma patients (average age 34, 76% men, 55% blunt mechanism, and with a median new injury severity score of 17) were included. Plasma and whole blood thrombin generation differed with more robust thrombin generation in plasma. Trauma patients had a significantly increased whole blood thrombin generation compared with healthy volunteers]. Plasma thrombin generation correlated with international normalized ratio, whereas whole blood thrombin generation did not correlate with thrombelastography. CONCLUSION: Plasma and whole blood thrombin generation are distinct, highlighting the need to perform standardized assays to better understand their correlation and to assess how whole blood thrombin generation confers differential outcomes in trauma.

Endogenous Procoagulant Activity in Trauma Patients and Its Relationship to Trauma Severity.

Background It has been observed that trauma patients have elevated plasma procoagulant activity that could be assigned to an elevated concentration of tissue factor (TF). However, in many instances there is a discrepancy between the levels of TF and the procoagulant activity observed. We hypothesized that factor XIa (FXIa) could be responsible for this additional activity and that the presence and levels of both proteins could correlate with trauma severity. Methods Citrate plasma from 98 trauma patients (47 blunt, 17 penetrating, and 34 thermal) were evaluated in clotting assays for the presence of FXIa and TF activity using respective inhibitory antibodies. Results When the three trauma patient groups were divided into two cohorts (Injury Severity Score [ISS] > 25 and ISS ≤ 25), higher frequencies and concentrations of both TF and FXIa were observed for all the more severe injury subgroups. Conclusions The majority of trauma patients have active FXIa in their plasma, with a significant fraction having active TF as well. Additionally, both TF and FXIa frequency and concentration directly relate to trauma severity. These data suggest the use of these two proteins as potential markers for the stratification of trauma patients.

Predictors of neutrophil extracellular traps markers in type 2 diabetes mellitus: associations with a prothrombotic state and hypofibrinolysis.

BACKGROUND: Type 2 diabetes mellitus (T2DM) is associated with a hypercoagulable state and increased neutrophil extracellular traps formation (NETosis). We investigated predictors of NETosis and cell death markers in circulating blood and their association with a prothrombotic state in T2DM. METHODS: In a cross-sectional study involving 113 T2DM patients aged 63.7 ± 8.2 years, we investigated citrullinated histone H3 (H3Cit), cell-free deoxyribonucleic acid (cfDNA), myeloperoxidase, neutrophil elastase, and inflammation markers, along with thrombin generation (TG), plasma clot lysis time (CLT), clot permeability (Ks) and fibrinolysis inhibitors. RESULTS: On multivariate logistic regression analysis adjusted for age and gender, predictors of high H3Cit (≥ 7.36 ng/mL, upper quartile) were: glycated hemoglobin (HbA1c) ≥ 7.0% and interleukin-6. Interleukin-6 was also found to be a predictor of high cfDNA (≥ 2.84 µg/mL, upper quartile) along with glucose. Citrullinated histone H3 and cfDNA correlated positively with CLT and inversely with Ks, while TG associated solely with cfDNA. These associations were not seen with myeloperoxidase and neutrophil elastase. Patients with previous myocardial infarction (n = 21, 18.6%) had higher H3Cit (+108%, p < 0.001) and cfDNA (+45%, p = 0.022). On multivariable analysis adjusted for potential confounders, H3Cit and cfDNA, along with plasminogen activator inhibitor-1 and concomitant cardiovascular disease, were predictors of CLT. Citrullinated histone H3 alone was a predictor of Ks and only cfDNA was a predictor of peak thrombin generated. CONCLUSIONS: In T2DM, NETosis detectable in circulating blood is associated with inflammatory state and a prothrombotic state, especially hypofibrinolysis.

Altered fibrin clot properties in advanced lung cancer: strong impact of cigarette smoking.

BACKGROUND: Dense fibrin networks resistant to lysis have been reported in patients at high risk of thromboembolism. Little is known about fibrin clot properties in cancer. We investigated fibrin clot properties and their determinants in patients with inoperable lung cancer. METHODS: We enrolled 150 patients with advanced lung cancer prior to therapy and 90 control subjects matched by age, sex, cardiovascular disease, and diabetes. Plasma clot permeability (Ks), turbidimetric analysis of clot formation, clot lysis time (CLT), microparticle-associated tissue factor (MP-TF) activity, thrombin generation, and serum cotinine levels were determined. RESULTS: Lung cancer patients, compared with controls, formed at a faster rate (- 8.1% lag phase) denser plasma fibrin networks (- 27.2% Ks) that displayed impaired lysis (+ 26.5% CLT), along with 19.5% higher MP-TF activity and 100% higher peak thrombin generated, also after adjustment for potential confounders. Cotinine levels were associated with fibrin maximum absorbance (r = 0.20, p = 0.016) and Ks (r = - 0.50, p < 0.0001) in cancer patients. On multivariate regression analysis, an increase in cotinine levels was a predictor of low Ks (the lower quartile, < 5.8 × 10-9 cm2; odds ratio = 1.21 per 10 ng/ml, 95% confidence interval 1.02-1.46), but not CLT. CONCLUSION: Advanced lung cancer is associated with the prothrombotic plasma clot phenotype largely driven by smoking.

Issues complicating precision dosing for factor VIII prophylaxis.

We previously showed that personalizing prophylaxis on the basis of an individual's pharmacokinetic (PK) response to factor VIII (FVIII) infusion reduces joint and other bleeding events in patients with hemophilia A. We theorized that the FVIII assay used, FVIII product selected, and interpatient differences impact PK assessment and the ability to precisely dose prophylaxis. A comprehensive search of the literature for articles published from January 2004 to September 2017 was performed to identify the variables associated with these three domains. Collectively, product- and patient-related assay discrepancies, variability among plasma-derived and unmodified and modified recombinant FVIII products, and interpatient differences in the response to FVIII infusions are obstacles to precision prophylactic dosing. Stringent laboratory quality assurance programs and proficiency testing to improve the accuracy of FVIII measurement, the widespread use of PK assessment to fine-tune FVIII dosing, and new research to identify patient characteristics and other contributors to bleeding risk and complication development are essential to optimizing outcomes for patients with hemophilia A receiving FVIII prophylaxis.

Continuous thrombin generation in whole blood: New applications for assessing activators and inhibitors of coagulation.

Hemostatic tests have been utilized to clarify the blood coagulation potential. The novel thrombin generation (TG) assay of this study provides explicit information and is the most physiologically-relevant hemostatic test ex vivo. We describe how this assay allows for TG under a number of relevant circumstances. First, whole blood (WB) from healthy individuals was analyzed ±â€¯5 pM tissue factor (TF) and ± contact pathway inhibition. Without an exogenous initiator TG was decreased and delayed, but addition of 5 pM TF shortened the lag phase and increased peak thrombin. Additional experiments included fresh WB from a trauma patient analyzed for endogenous activity and TG from healthy donors subjected to TG antagonists which prolonged the lag phase whereas TG agonists consistently shortened the lag phase in a dose dependent manner. Lastly, platelet-poor plasma was reconstituted with packed red blood cells and TG was monitored in the presence and absence of both TF as an activator and PCPS as a phospholipid surface. Our data illustrate the potential that this continuous TG assay has in the evaluation of disorders relevant to blood coagulation and in the monitoring of treatments administered in response to these disorders.

Altered fibrin clot properties in advanced lung cancer: impact of chemotherapy.

BACKGROUND: Faster formation of dense and poorly lyzable fibrin networks have been reported in patients at risk of thromboembolism, including cancer patients. We sought to investigate whether chemotherapy affects plasma fibrin clot properties and their determinants in lung cancer patients. METHODS: In this observational study we enrolled 83 consecutive patients with advanced inoperable lung cancer. Plasma fibrin clot permeability (Ks), turbidimetric analysis of clot formation, clot lysis time (CLT), microparticle-associated tissue factor (MP-TF) activity, and thrombin generation parameters were investigated at enrolment and 3-4 months after standard chemotherapy. RESULTS: Lung cancer patients after 4 (range, 4-5) cycles of chemotherapy had 35.6% higher D-dimer, 22.1% lower MP-TF activity, and unaltered fibrinogen compared with baseline. Chemotherapy resulted also in 7.5% increased Ks, 8.6% prolonged lag phase, and 5.4% shortened CLT, while thrombin generation was unchanged. Chemotherapy-related differences in clot structure were confirmed by scanning electron microscopy images. Fibrin clot properties after chemotherapy did not differ among histological types of lung cancer, cancer stages or chemotherapy regimens. Interestingly, never smoking (n=13, 16%) was associated with looser post-treatment fibrin structure as reflected by 12.3% higher Ks. Multiple linear regression showed that more advanced cancer stage, higher peak thrombin generation, and higher white blood cell count determined post-treatment change in Ks, while active smoking was associated with change in CLT. CONCLUSIONS: Three-month chemotherapy in lung cancer patients improves clot properties despite unaffected thrombin generation, suggesting that anticancer treatment might quickly produce antithrombotic actions.

Analysis of factor XIa, factor IXa and tissue factor activity in burn patients.

INTRODUCTION: An elevated procoagulant activity observed in trauma patients is, in part, related to tissue factor (TF) located on blood cells and microparticles. However, analysis of trauma patient plasma indicates that there are other contributor(s) to the procoagulant activity. We hypothesize that factor (F)XIa and FIXa are responsible for an additional procoagulant activity in burn patients. METHODS: Multiple time-point plasma samples from 56 burn patients (total number of samples was 471; up to 20 time-points/patient collected in 3 weeks following admission) were evaluated in a thrombin generation assay using inhibitory antibodies to TF, FIXa and FXIa. RESULTS: Due to the limited volume of some samples, not all were analyzed for all three proteins. At admission, 10 of 53 patients (19%) had active TF, 53 of 55 (96%) had FXIa and 48 of 55 (87%) had FIXa in their plasma. 34 patients of 56 enrolled (61%) showed TF activity at one or more time-points. All patients had FXIa and 96% had FIXa at one or more time-points. Overall, TF was observed in 99 of 455 samples analyzed (22%), FXIa in 424 of 471 (90%) and FIXa in 244 of 471 (52%). The concentration of TF was relatively low and varied between 0 and 2.1pM, whereas that of FXIa was higher, exceeding 100pM in some samples. The majority of samples with FIXa had it at sub-nanomolar concentrations. No TF, FXIa and FIXa activity was detected in plasma from healthy individuals. CONCLUSIONS: For the first time reported, the majority of plasma samples from burn patients have active FXIa and FIXa, with a significant fraction of them having active TF. The concentration of all three proteins varies in a wide range.