Thrombin Generation Parameters Research Articles

Relationship between plasma tissue Factor Pathway Inhibitor (TFPI) levels, thrombin generation and clinical risk of bleeding in patients with severe haemophilia A or B.

Bleeding severity in severe haemophilic patients, with low thrombin generation (TG) capacity, can vary widely between patients, possibly reflecting differences in tissue factor pathway inhibitor (TFPI) level. To compare free TFPI (fTFPI) levels in patients with severe haemophilia A (sHA) and severe haemophilia B (sHB) and to investigate in these patients as a whole the relationships between bleeding and TG potential, between TG potential and fTFPI level and between fTFPI level and bleeding tendency. Data on bleeding episodes retrospectively recorded during follow-up visits over 5-10 years were collected and used to calculate the annualised joint bleeding rate (AJBR). fTFPI levels and basal TG parameters were determined in platelet-poor plasma (PPP) and platelet-rich plasma (PRP) using calibrated automated tomography (CAT). Mean fTFPI levels did not differ significantly between sHA (n=34) and sHB (n=19) patients. Mean values of endogenous thrombin potential (ETP) and thrombin peak (peak) in PPP and PRP were two-fold higher when fTFPI levels<9.4 versus>14.3ng/mL. In patients treated on demand, ETP and peak in PRP were doubled when AJBR was , AJBR being halved in patients with a low fTFPI level (9.4ng/mL). In patients on factor prophylaxis, no association was found between TG parameters and either fTFPI level or AJBR. In patients treated on demand, bleeding tendency was influenced by fTFPI levels, which in turn affected basal TG potential. In patients on prophylaxis, bleeding tendency is probably determined primarily by the intensity of this treatment.

Investigation of thrombin concentration at the time of clot formation in simultaneous thrombin and fibrin generation assays

Thrombin generation (TG) and fibrin clot formation represent the central process of blood coagulation. Up to 95% of thrombin is considered to be generated after the clot is formed. However, this was not investigated in depth. In this study, we conducted a quantitative analysis of the Thrombin at Clot Time (TCT) parameter in 5758 simultaneously recorded TG and clot formation assays using frozen plasma samples from commercial sources under various conditions of activation. These samples were supplemented with clotting factor concentrates, procoagulant lipid vesicles and a fluorogenic substrate and triggered with tissue factor (TF). We found that TCT is often close to a 10% of thrombin peak height (TPH) yet it can be larger or smaller depending on whether the sample has low or high TPH value. In general, the samples with high TPH are associated with elevated TCT. TCT appeared more sensitive to some procoagulant phenotypes than other commonly used parameters such as clotting time, TPH or Thrombin Production Rate (TPR). In a minority of cases, TCT were not predicted from TG parameters. For example, elevated TCT (above 15% of TPH) was associated with either very low or very high TPR values. We conclude that clotting and TG assays may provide complementary information about the plasma sample, and that the TCT parameter may serve as an additional marker for the procoagulant potential in plasma sample.

Longitudinal assessment of coagulation potential before, during, and following an in vitro fertilization cycle

IntroductionThe association between estrogen and hypercoagulability is well-established but little is known about coagulation dynamics during IVF. Our goal was to measure coagulation potential prior to, during, and following an IVF cycle and to investigate differences by conception outcome. Materials and methodsPatients undergoing IVF with fresh embryo transfer at a single academic center using oral contraceptive pills for cycle batching underwent evaluation of thrombin generation using the calibrated automated thrombogram at multiple points during the IVF cycle. Multiple thrombin generation parameters were compared across timepoints and by IVF cycle outcome using ANOVA repeated measures analysis. ResultsOf the 17 patients included, 11 conceived. There was a significant increase in peak and total thrombin generation in the entire cohort between the pre-treatment natural follicular phase and following a short course of oral contraceptive pills used for cycle batching. Further increase in these parameters was seen at the time of oocyte retrieval. In the pre-treatment natural follicular phase, patients who conceived had lower peak thrombin generation. There were changes throughout the cycle for factors II, V, VIII, X, XI, XII, antithrombin, and tissue factor pathway inhibitor. Only Factor XI was distinguishable by conception status; values were lower at all visits in patients who conceived. ConclusionIncreases in coagulation potential are seen in patients undergoing IVF following a short course of oral contraceptive pills for cycle batching and continue during controlled ovarian hyperstimulation. Those who conceived were seen to have lower peak thrombin generation in the pre-treatment natural follicular phase.

Ponatinib Induces a Procoagulant Phenotype in Human Coronary Endothelial Cells via Inducing Apoptosis.

BCR-ABL tyrosine kinase inhibitors (TKIs) are effective drugs in the treatment of patients with chronic myeloid leukemia. However, based on clinical studies, ponatinib was associated with the development of thrombotic complications. Since endothelial cells (ECs) regulate blood coagulation, their abnormal phenotype may play a role in the development of thrombotic events. We here aimed to investigate the effect of ponatinib on the procoagulant activity of cultured endothelial cells in vitro. Human coronary artery endothelial cells (HCAECs) were incubated with 50, 150, and 1000 nM of ponatinib. Subsequently, phosphatidylserine (PS) exposure and endothelial microvesicles (EMVs) were measured by flow cytometry. In addition, EC- and EMV-dependent thrombin generation was analyzed. To investigate pro-apoptotic effects of ponatinib, the level of Bax and Bcl-xL proteins were studied using Western blot and F3, THBD, and VCAM1 mRNAs were quantified by qPCR. Therapeutic concentrations of ponatinib significantly increased PS expression on ECs and the amount of EMVs which significantly shortened the time parameters of thrombin generation. In addition, these changes were associated with an increased ratio of Bax and Bcl-xL proteins in the presence of the decreased THBD mRNA level. Overall, ponatinib enhances the procoagulant activity of ECs via inducing apoptosis, which may contribute to thrombotic events.

Exploring the effects of Factor Xa inhibitors on thrombin generation in people with haemophilia

Optimal management of cardiovascular disease (CVD) in people with haemophilia (PWH) is a growing issue, given the continuing improvement in life expectancy among PWH. The evolving treatment paradigms targeting higher trough levels and the advent of non-factor replacement therapies (NFRT) means much of the ‘protection’ PWH were thought to have against CVD may be lost. There is a paucity of evidence regarding the safety of using anticoagulants in PWH. We designed a study assessing the thrombin generation (TG) of PWH of different severities and treatments, compared to non-haemophilia patients receiving a Factor Xa (FXa) inhibitor (apixaban or rivaroxaban), healthy controls, and assessing TG parameters of adding FXa inhibitor to the plasma of PWH receiving emicizumab prophylaxis. In total, 40 patients were included. TG was initiated with 5pM tissue factor (TF) using the calibrated automated thrombinoscope. Compared to those with mild haemophilia, patients receiving a FXa inhibitor had higher endogenous thrombin potential (ETP) (1278.42 vs 1831.36) and velocity index (40.71 vs 112.56), but both had a similar peak height (154.0 vs 262.63) and time to peak (both 5.83). People with severe haemophilia receiving emicizumab had significantly improved TG parameters compared to those not receiving emicizumab – ETP 1678.11 vs 809.96 and peak height 233.8 vs 92.05; however, when FXa inhibitor was added their TG parameters deteriorated to the severe haemophilia range (ETP 1179.60 and peak height 103.05). TG may provide additional useful information regarding the use of anticoagulants in PWH.

Endogenous thrombin potential and time-dependent thrombin generation parameters are independent risk factors for mortality in the general population

BackgroundThrombin generation (TG) is used as a global test of coagulation and is an indicator of thrombosis and bleeding risk. Until now, data on the association of TG and mortality are inconclusive. ObjectivesWe investigated the association between TG and mortality in the prospective Moli-sani cohort (n = 21 920). MethodsTG was measured using calibrated automated thrombinography using PPP-Reagent Low. Lag time (LT), endogenous thrombin potential (ETP), peak height, time-to-peak (TTP), and velocity index were quantified. The association of TG and mortality was studied by Cox regression and adjusted for sex, age, body mass index, smoking, contraceptives, and medical history (cardiovascular diseases, hypertension, hypercholesterolemia, diabetes, and cancer). ResultsLT and TTP were 4.1 ± 1.0 minutes and 6.6 ± 1.5 minutes, on average. The peak height was 364 ± 88 nM, velocity index was 163 ± 63 nM/min, and ETP was 1721 ± 411 nM·min. ETP was negatively associated with all-cause mortality (hazard ratio [HR], 0.86; 95% CI, 0.81-0.92; P < .001). Subjects in the lowest quintile of the ETP (ETPQ1) had a 1.3-fold higher mortality rate. Additionally, a high TTP/LT ratio was negatively associated with mortality (HR, 0.71; 95% CI, 0.57-0.89; P = .003). Individuals in quintile 1 of the TTP/LT ratio had a 1.4-fold higher mortality rate compared with the remainder of the cohort. Subjects that were both in ETPQ1 and TTP/LTQ1 had a 1.8-fold higher mortality rate, regardless of whether they reported history of cardiovascular disease at baseline (HR, 1.61 [CI: 1.07-2.42]) or not (HR, 1.89 [CI: 1.51-2.36]). ConclusionLow ETP and TTP/LT ratios are independent risk factors for all-cause mortality in the general population.

Pharmacokinetic-Pharmacodynamic Modelling in Hemophilia A: Relating Thrombin and Plasmin Generation to Factor VIII Activity After Administration of a VWF/FVIII Concentrate.

Hemophilia A patients are treated with factor (F) VIII prophylactically to prevent bleeding. In general, dosage and frequency are based on pharmacokinetic measurements. Ideally, an alternative dose adjustment can be based on the hemostatic potential, measured with a thrombin generation assay (TGA), like the Nijmegen hemostasis assay. The objective of this study was toinvestigate the predicted performance of a previously developed pharmacokinetic-pharmacodynamic model for FVIII replacement therapy, relating FVIII dose and FVIII activity levels with thrombin and plasmin generation parameters. Pharmacokinetic and pharmacodynamic measurements were obtained from 29 severe hemophilia A patients treated with pdVWF/FVIII concentrate (Haemate P®). The predictive performance of the previously developed pharmacokinetic-pharmacodynamic model was evaluated using nonlinear mixed-effects modeling (NONMEM). When predictions of FVIII activity or TGA parameters were inadequate [median prediction error (MPE) > 20%], a new model was developed. The original pharmacokinetic model underestimated clearance and was refined based on a two-compartment model. The pharmacodynamic model displays no bias in the observed normalized thrombin peak height and normalized thrombin potential (MPE of 6.83% and 7.46%). After re-estimating pharmacodynamic parameters, EC50 and Emax values were relatively comparable between the original model and this group. Prediction of normalized plasmin peak height was inaccurate (MPE 58.9%). Our predictive performance displayed adequate thrombin pharmacodynamic predictions of the original model, but a new pharmacokinetic model was required. The pharmacodynamic model is not factor specific and applicable to multiple factor concentrates. A prospective study is needed to validate the impact of the FVIII dosing pharmacodynamic model on bleeding reduction in patients.

Association between venous thromboembolism-associated genetic variants, coagulation factor levels, and thrombin generation potential.

Recently three large meta-analyses of genome-wide association studies for venous thromboembolism (VTE) identified over 130 genetic variants. However, mechanisms by which newly identified and therefore underexplored VTE-associated genetic variants influence VTE remain unclear. To elucidate the mechanism, we investigated the association between 61 newly identified VTE-associated genetic variants and the levels of coagulation factor (F) VIII, FIX, FXI, and fibrinogen as well as thrombin generation parameters (lag time, peak, endogenous thrombin potential, time-to-peak, and velocity), which are well-known biological traits associated with VTE. This study was conducted on 5341 participants of the Netherlands Epidemiology of Obesity study. The associations between VTE-associated genetic variants and coagulation factor levels and thrombin generation parameters were examined using linear regression analyses, adjusted for age, sex, body mass index, oral contraceptive use, hormone replacement therapy, and menopausal status. Of 61 genetic variants, 33 were associated with one or more of the coagulation factor levels and thrombin generation parameters. Following multiple testing corrections, five genetic variants remained significant, of which MAP1A rs55707100 exhibited the most robust association with thrombin generation parameters and FXI levels (β=-5.33%, 95% confidence interval: -8.44, -2.22). Our findings shed light on the underlying mechanisms by which these genetic variants influence the risk of VTE.

A thrombin-driven neural net diagnoses the antiphospholipid syndrome without the need for interruption of anticoagulation

AbstractThrombosis is an important manifestation of the antiphospholipid syndrome (APS). The thrombin generation (TG) test is a global hemostasis assay, and increased TG is associated with thrombosis. APS is currently diagnosed based on clinical and laboratory criteria, the latter defined as anti-cardiolipin, anti–β2-glycoprotein I antibodies, or lupus anticoagulant (LA). APS testing is often performed after a thrombotic episode and subsequent administration of anticoagulation, which might hamper the interpretation of clotting assays used for LA testing. We set out to develop an artificial neural network (NN) that can diagnose APS in patients who underwent vitamin K antagonist (VKA) treatment, based on TG test results. Five NNs were trained to diagnose APS in 48 VKA-treated patients with APS and 64 VKA-treated controls, using TG and thrombin dynamics parameters as inputs. The 2 best-performing NNs were selected (accuracy, 96%; sensitivity, 96%-98%; and specificity, 95%-97%) and further validated in an independent cohort of VKA-anticoagulated patients with APS (n = 33) and controls (n = 62). Independent clinical validation favored 1 of the 2 selected NNs, with a sensitivity of 88% and a specificity of 94% for the diagnosis of APS. In conclusion, the combined use of TG and NN methodology allowed for us to develop an NN that diagnoses APS with an accuracy of 92% in individuals with VKA anticoagulation (n = 95). After further clinical validation, the NN could serve as a screening and diagnostic tool for patients with thrombosis, especially because there is no need to interrupt anticoagulant therapy.

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

BackgroundTamoxifen is an effective treatment for primary breast cancer but increases the risk for venous thromboembolism. Tamoxifen decreases anticoagulant proteins, including antithrombin (AT), protein C (PC) and tissue factor (TF) pathway inhibitor, and enhances thrombin generation (TG). However, the relation between plasma concentrations of both tamoxifen and its active metabolite endoxifen and coagulation remains unknown. MethodsTamoxifen and endoxifen were measured in 141 patients from the prospective open-label intervention TOTAM-study after 3 months (m) and 6 m of tamoxifen treatment. Levels of AT and PC, the procoagulant TF, and TG parameters were determined at both timepoints if samples were available (n = 53–135 per analysis). Levels of coagulation proteins and TG parameters were correlated and compared between: 1) quartiles of tamoxifen and endoxifen levels, and 2) 3 m and 6 m of treatment. ResultsAt 3 m, levels of AT, PC, TF and TG parameters were not associated with tamoxifen nor endoxifen levels. At 6 m, median TF levels were lower in patients in the 3rd (56.6 [33] pg/mL), and 4th (50.1 [19] pg/mL) endoxifen quartiles compared to the 1st (lowest) quartile (76 [69] pg/mL) (P=0.027 and P=0.018, respectively), but no differences in anticoagulant proteins or TG parameters were observed. An increase in circulating TF levels (3 m: 46.0 [15] versus 6 m: 54.4 [39] pg/mL, P < 0.001) and TG parameters was observed at the 6 m treatment timepoint, while AT and PC levels remained stable. ConclusionsOur results indicate that higher tamoxifen and endoxifen levels are not correlated with an increased procoagulant state, suggesting tamoxifen dose escalation does not further promote hypercoagulability.

A Short Thrombin Generation Time-to-Peak/Lag Time Ratio Is an Independent Risk Factor for Mortality in the General Population

Background Thrombin generation (TG) is used to detect small changes in coagulation indicating a bleeding or prothrombotic phenotype. Until now, large prospective studies are missing to study the association of TG parameters with the occurrence of future cardiovascular events and mortality. In this study, we investigated the prospective value of TG measured in baseline plasma samples of a large cohort (n=20,991) with overall mortality (1,098; 5.3%) with a median follow-up of 8.2 years. Methods Thrombin generation was measured by calibrated automated thrombinography (CAT) using PPP Reagent low. The lag time (LT), endogenous thrombin potential (ETP), peak height, time-to-peak (TTP) and velocity index (VI) were quantified. Subjects on anticoagulant therapy were excluded from analysis, because this affects the measurement of TG. Cox regression was used to analyze differences in survival in subjects according to their variations in the TG parameters. The reported results are obtained from a crude model considering only single TG parameters standardized for their standard deviation, and from a final multivariable model further adjusted for sex, age, BMI, smoking, contraceptive use, antiplatelet medication and medical history (hypertension, hypercholesterolemia, diabetes, history of cardiovascular diseases or cancer). Results The TG lag time at 1 pM tissue factor was 4.1 min ± 1.0 on average, and the peak height was 363 nM ± 89. The time-to-peak was 6.6 min ± 1.6 on average, the velocity index was 163 nM/min ± 63 and the endogenous thrombin potential was 1717 nM·min ± 415. The SD-standardized lag time was significantly associated with mortality risk in the crude model (HR LT=1.09; CI:1.03-1.16; p=0.002) and after adjustment for all covariates, including medical history (HR LT=1.09; CI: 1.03-1.15; p=0.002). In contrast, a short time-to-peak was significantly associated with reduced mortality risk (HR TTP=0.92; CI: 0.86-0.98; p=0.012). As the opposite associations of LT and TTP with mortality could have a synergistic effect on the mortality risk, we combined the variables into the novel TTP/LT-ratio. The mean TTP/LT ratio was 1.61 ± 0.14. The hazard ratio for mortality decreased by 40% for each standard deviation increment of the TTP/LT-ratio in the crude model (HR ratio=0.606; CI:0.562-0.654; p&amp;lt;0.001), and by 18% in the fully adjusted model (HR ratio=0.824; CI: 0.766-0.887; p&amp;lt;0.001). The TTP/LT-ratio variable was divided in quintiles for further analysis: Quintile 1 included subjects up to a TTP/LT-ratio of 1.50, quintile 2 ranged from 1.50 to 1.58, quintile 3 ranged from 1.58 to 1.62, quintile 4 ranged from 1.62 to 1.70, and quintile 5 consisted of subjects with a TTP/LT-ratio above 1.70. Subjects in TTP/LT-ratio quintile 1 had an increased mortality risk (HR ratio_Q1vsQ5 =2.96; CI: 2.42-3.63; p&amp;lt;0.001), even after full adjusting (HR ratio_Q1vsQ5 =1.46; CI: 1.18-1.79; p&amp;lt;0.001; Figures 1 and 2). Moreover, subjects in TTP/LT-ratio quintile 2, have a similar statistically significant, although less pronounced increase risk for mortality in the crude model (HR ratio_Q1vsQ5 =2.17; CI: 1.18-2.68; p&amp;lt;0.001) and the fully adjusted model (HR ratio_T2vsT5 =1.29; CI: 1.04-1.60; p=0.019; Figure 1). Conclusion A prolonged TG lag time and a shortened time-to-peak in the general population and within the normal ranges are risk factors for mortality. The combination of a long LT and a short TTP results in a low TTP/LT-ratio, which was identified as an independent risk factor for increased mortality risk in the general population.

Diversity of Plasmatic Thrombin Pools Regulate Thrombin Generation and Blood Clotting: Interference By a Novel Nanobody

Background: Thrombin has a multitude of roles in the initiation and propagation of (anti)coagulation, in platelet activation and fibrin clot formation. The assessment of thrombin generation (TG) and thrombin-dynamics, combined with multi-omics data, has provided in-depth understanding of the plasma factors contributing to the (in)activation of thrombin in triggered plasma and whole-blood. By default, the generated thrombin is considered to act as a single pool. Here, we present evidence for at least two major proteolytically active thrombin pools with non-overlapping functions in blood clotting. Methods: A novel Syn-Nb-AF106 anti-fibrin nanobody (Nb106) was characterized, targeting a species-conserved thrombin-binding site exposed by fibrinopeptide A cleavage from fibrinogen (Sun et al, this meeting). Thrombin generation was assessed by calibrated automated thrombography using various triggers with control (multi-donor) and (reconstituted) coagulation factor-deficient plasmas, platelet-rich plasma or whole blood. Fibrin clot formation was evaluated by scanning electron microscopy (SEM). Clot retraction was macroscopically assessed. Results: In tissue factor-triggered thrombin generation,we discovered that Nb106 dose-dependently reduced the thrombin peak level and endogenous thrombin potential (ETP) to 54-62%, without affecting kinetic thrombin generation parameters. We observed a similar reduction in platelet-free plasma, platelet-rich plasma and whole blood. Biochemically, Nb106 displaced thrombin from a binding site on cleaved fibrinogen (Sun et al., abstract). Nb106 inhibited tissue factor-induced thrombin generation, using plasma deficient in factor IX, XI or XII, but not using plasmas deficient in fibrinogen or antithrombin. Reconstitution experiments showed that the inhibition depended on the fibrinogen concentration. A-specific control nanobodies were without effect. Together, the fibrin(ogen)-dependent and thrombin-inhibiting effect indicated that Nb106 operates by releasing proteolytically-active thrombin from fibrin to allow inactivation by antithrombin. Time-dependent, late spiking experiments revealed that Nb106 reduced the generation of thrombin only when added at 0-15 minutes after trigger, but no longer after 30 minutes, suggesting that the inhibitory capacity was due to a shortened thrombin binding to fibrin rather than to a continued protection towards antithrombin. In plasmas from a cohort of 64 healthy subjects, application of Nb106 showed a consistent reducing effect on the parameters peak and ETP, with a moderate positive correlation with the fibrinogen level. Nb106 suppressed the thrombin generation amplitude, but not the kinetics in the presence of a panel of direct oral anticoagulants (DOAC). Strikingly, brightfield microscopy and SEM indicated that Nb106, but not control nanobodies, in triggered plasma, platelet-rich plasma and whole-blood, fully abrogated the formation of elongating fibrin fibers. In agreement with this, it strongly suppressed whole-blood clot retraction. Conclusion: Collectivity, these data point to the existence of two major pools of proteolytically active thrombin, both of which contributing to thrombin generation, that are formed upon plasma and blood coagulation. One pool of soluble thrombin steers the proteolytic coagulation cascade, while another pool is bound to growing fibrin fibers. The latter pool still cleaves the conventional AMC thrombin substrate, is temporarily protected against antithrombin, and is required for fibrin fiber extension and blood clotting and clot retraction. The Nb106, replacing thrombin from its binding site on fibrin, selectively annuls the second pool, thereby blocking the clotting process. The replacement ensures thrombin inactivation by antithrombin. Perspective: The novel anti-fibrin nanobody Syn-Nb-AF106 or a derivative has the potential to act as an alternative anticoagulant in thrombotic diseases with pathological fibrin formation.

The effect of factor XIa on thrombin and plasmin generation, clot formation, lysis and density in coagulation factors deficiencies

IntroductionGrowing evidence supports the importance of factor (F) XI activation for thrombosis and hemostasis as well as inflammation and complement systems. In this study, we evaluated the effect of activated FXI (FXIa) on the detection of factor deficiencies by global hemostasis assays of thrombin generation (TG), plasmin generation (PG), and clot formation and lysis (CFL). Materials and methodsAn absorbance and fluorescence microplate assay was used to simultaneously observe TG, PG, and CFL in FV-, FVII-, FVIII-, and FIX-deficient plasmas supplemented with purified factors. Coagulation was initiated with tissue factor with or without FXIa in the presence of tissue plasminogen activator. Thrombin and plasmin peak heights (TPH and PPH), maximal clot density (MCD), times to clotting (CT), thrombin and plasmin peaks (TPT and PPT) and clot lysis (LyT) and a new parameter, clot lifetime (LiT), were evaluated. ResultsTG/CFL were elevated by the FXIa at low FV (below 0.1 IU/mL), and at FVIII and FIX above 0.01 IU/mL. FXIa affected PG only at low FV and FVII. At high factor concentrations, FXIa reduced MCD. Thrombin and plasmin substrates had effect on CT, LyT, LiT and MCD parameters. ConclusionsFXIa reveals new relationships between TG, PG and CFL parameters in factor deficiencies suggesting potential benefits for discrimination of bleeding phenotypes.

Global tests in patients with Ph-negative myeloproliferative neoplasms

Introduction: A frequent clinical manifestation of Ph-negative myeloproliferative neoplasms (MPN) is the development of thrombosis. To identify the state of hypercoagulation it is relevant and promising to introduce global tests for evaluating the hemostasis — the thrombin generation test (TGT) and thromboelastography (TEG). Aim: to evaluate the parameters of thrombin generation and thromboelastography in patients with Ph-negative MPN. Material and methods. In total, 62 patients with MNP were included in the study: 27 with polycythemia vera (PV), 14 with essential thrombocythemia (ET) and 21 with primary myelofibrosis (PMF). The control group included 55 practically healthy individuals, comparable in gender and age (19 people in the study of TEG, 36 people in the study of TGT). The TEG was performed using a “TEG 5000” thromboelastograph. TGT was measured with Calibrated Automated Thrombinography. Results: Ly30 and Ly60 in TEG in patients were significantly lower (0.35 (0.20–0.48), 0.00 (0.00–0.40) and 0.00 (0.00 — 0.43) and 3.15 (2.45–3.60), 1.25 (0.10–3.58) and 0.60 (0.00–3.05) respectively), than in the control (1.60 (1.05–2.75) and 6.20 (4.15–8.30), respectively), which indicates the ineffectiveness of fibrinolysis. The values of MA and G in patients with ET and PV significantly exceeded the control (69.15 (67.98–70.78) mm and 65.20 (59.65–63.83) mm versus 62.00 (57.75–6.75) mm and 11.20 (10.60–12.15) din/cm2 and 9.40 (7.40–11.60) din/cm2 versus 8.20 (6.85–8.75) din/cm2, respectively. The most pronounced change in sensitivity to TM was observed in patients with ET (27.94 (17.35–43.58) % and 13.29 (-3.48–23.60) %, respectively; p &lt; 0.05). A significant decrease in ETP was observed in patients with PV and PMF. Conclusion. The study of hemostasis in patients with MPN using TEG and TGT revealed the presence of multidirectional changes associated with the disease. The TEG showed that an increase in the time required for the onset of fibrin formation is combined with increased clot strength and inhibited fibrinolysis, which are risk factors for the development of thromboembolic complications. The study of TGT determined a decrease in the quantitative characteristics of thrombin generation and at the same time the failure of the anticoagulant system of protein C, leading to the development of hypercoagulation.

Bleeding phenotype and hemostatic evaluation by thrombin generation in children with Noonan syndrome: A prospective study.

This study aimed to evaluate the bleeding phenotype and to conduct a comprehensive hemostatic evaluation in individuals with Noonan syndrome (NS), a dominantly inherited disorder caused by pathogenic variants in genes associated with the Ras/MAPK signaling pathway. Children with a genetically confirmed diagnosis of NS underwent clinical evaluation, routine laboratory tests, platelet function testing, and thrombin generation (TG) assessment. The study included 24 children. The most frequently reported bleeding symptoms were easy bruising and epistaxis, while bleeding complications were observed in 15% of surgical procedures. Various hemostatic abnormalities were identified, including platelet dysfunction, von Willebrand disease, and clotting factor deficiencies. Abnormal platelet function was observed in 50% of the patients, and significantly lower TG parameters were found compared to controls. However, no significant correlation was observed between bleeding symptoms and TG results. The study suggests that the bleeding diathesis in NS is multifactorial, involving both platelet dysfunction and deficiencies of plasma coagulation factors. The potential role of TG assay as an ancillary tool for predicting bleeding tendencies in individuals with NS undergoing surgery warrants further investigation.

Hemostasis Biomarkers and Long-Term Risk of Recurrent Cardiovascular Events and Bleeding Complications in Young Patients with an Ischemic Stroke

Background: Patients with ischemic stroke at a young age (18-50 years) have a persistent increased risk of recurrent ischemic cardiovascular events, despite antithrombotic treatment. Additionally, antithrombotic agents result in a higher risk of bleeding complications. Balancing hemostasis to prevent thrombotic events and minimizing the risk of hemorrhagic events is challenging. Previous research observed a hypercoagulable state and a significant degree of inflammation years after an acute ischemic stroke in young adults. It is known that an increased clotting tendency is a risk factor for a first ischemic stroke, especially in young adults. However, the risk profile of a recurrent event in these individuals can be different. To this end, our study aims to investigate the role of plasma pro- and anticoagulation biomarkers, platelet activation markers and thrombin generation parameters in the risk of recurrent ischemic arterial events and bleeding complications after a first ischemic stroke or transient ischemic attack (TIA) at a young age. Method: Patients from a single-center cohort study (the FUTURE cohort) with a first-ever TIA or ischemic stroke event between 1980 and 2010 were included. Blood was collected in 2010 and patients were followed on recurrent ischemic events or bleeding complications between 2010 and 2023. The following coagulation parameters were measured: blood cell count, Von Willebrand factor, active Von Willebrand factor, factor VIII, prothrombin, fragment 1.2, d-dimer, fibrinogen, fibrin degradation products, antithrombin, alpha-2-macroglobulin, serum CXCL-4 and CXCL-7. In addition, thrombin generation (TG) was determined using 1pM and 5pM tissue factor, and thrombomodulin in platelet-poor plasma to assess the functional capacity of plasma to form thrombin. The primary outcome was a composite of recurrent ischemic stroke, TIA, acute coronary syndrome or peripheral artery disease. The secondary outcome was the occurrence of a bleeding complication using the Bleeding Academic Research Consortium (BARC) criteria. We applied Cox proportional hazard models to estimate hazard ratios (HR) with 95% confidence intervals (CI). Results : Among 378 patients (median age 42.1 years, 56% women), 74 experienced a recurrent ischemic event during a mean follow-up of 6.5 years. An increased platelet and leukocyte count, along with elevated levels of fragment 1.2, fibrinogen and D-dimer were associated with a higher risk of ischemic events (table 1). Patients with low plasma antithrombin activity had a higher risk of recurrent ischemic events, especially in women (HR 0.67 [0.47-0.96]). After adjustment for age, sex and traditional risk factors, the association between leukocytes numbers, fragment 1.2 and fibrinogen levels and antithrombin activity and the risk of recurrent ischemic events remained: HR 1.14 [1.05-1.25], 1.07 [1.01-1.14], 0.80 [0.65-0.98], and 1.09 [1.00-1.17], respectively. In patients without vitamin K antagonist treatment, the association between antithrombin activity (HR 0.78 [0.62-0.98]) and leukocytes numbers (HR 1.15 [1.05-1.25]) with recurrent ischemic events were stronger. Thrombin generation parameters were not related to recurrence. Bleeding complications were observed in 16% of patients, mainly among women and predominantly attributable to gynecological bleedings. Hemoglobin, platelets, CXCL-4 and -7, prothrombin, fragment 1.2 and alpha-2-macroglobulin were associated with a bleeding complication (table 2). The association for platelets (HR 0.93 [0.89-0.97]), CXCL-4 (HR 0.90 [0.82-0.99]) and alpha-2-macroglobulin (HR 1.15 [1.03-1.29]) remained after adjustment. Conclusion: Lower antithrombin activity and, higher fragment 1.2, fibrinogen levels, and leukocytes counts were linked to an increased risk of recurrent ischemic events. Bleeding was associated with platelets, CXCL4, and alpha-2-macroglobulin. Overall, especially platelets appear to be significantly involved in the risk of both recurrent arterial thrombosis and bleeding, whereas the observed association with risk of recurrent ischemic events implies a more dominant role of the coagulation system.

Sources of bias and limitations of thrombinography: inner filter effect and substrate depletion at the edge of failure algorithm

BackgroundFluorogenic thrombin generation (TG) is a global hemostasis assay that provides an overall representation of hemostasis potential. However, the accurate detection of thrombin activity in plasma may be affected by artifacts inherent to the assay-associated fluorogenic substrate. The significance of the fluorogenic artifacts or their corrections has not been studied in hemophilia treatment applications.MethodsWe sought to investigate TG in hemophilia plasma samples under typical and worst-case fluorogenic artifact conditions and assess the performance of artifact correction algorithms. Severe hemophilic plasma with or without added Factor VIII (FVIII) was evaluated using commercially available and in-house TG reagents, instruments, and software packages. The inner filter effect (IFE) was induced by spiking elevated amounts of fluorophore 7-amino-4-methylcoumarin (AMC) into plasma prior to the TG experiment. Substrate consumption was modeled by adding decreasing amounts of Z-Gly-Gly-Arg-AMC (ZGGR-AMC) to plasma or performing TG in antithrombin deficient plasma.ResultsAll algorithms corrected the AMC-induced IFE and antithrombin-deficiency induced substrate consumption up to a certain level of either artifact (edge of failure) upon which TG results were not returned or overestimated. TG values in FVIII deficient (FVIII-DP) or supplemented plasma were affected similarly. Normalization of FVIII-DP resulted in a more accurate correction of substrate artifacts than algorithmic methods.ConclusionsCorrection algorithms may be effective in situations of moderate fluorogenic substrate artifacts inherent to highly procoagulant samples, but correction may not be required under typical conditions for hemophilia treatment studies if TG parameters can be normalized to a reference plasma sample.

PB0990 Changes in Thrombin Generation Parameters in Newly Diagnosed Multiple Myeloma Patients in Response to Anti-Myeloma Therapy

PB0990 Changes in Thrombin Generation Parameters in Newly Diagnosed Multiple Myeloma Patients in Response to Anti-Myeloma Therapy

PB0099 Thrombin Generation Parameters Results in COVID Patients Comparing with Healthy Volunteers

PB0099 Thrombin Generation Parameters Results in COVID Patients Comparing with Healthy Volunteers

PB1052 Evaluating the Individual Risk of Venous Thrombo-Embolism in Patients with Liver Cirrhosis: Usefulness of in vivo and ex vivo Thrombin Generation Parameters

PB1052 Evaluating the Individual Risk of Venous Thrombo-Embolism in Patients with Liver Cirrhosis: Usefulness of in vivo and ex vivo Thrombin Generation Parameters