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Introduction: Unfolded Von Willebrand Factor (VWF) is increased in thrombotic pathologies such as myocardial infarction. Unfolded VWF mediates the binding of platelets without the need for collagen. β 2 -glycoprotein I (β 2 -GPI) is a natural inhibitor of the platelet-VWF interaction. The antiphospholipid syndrome (APS) is associated with thrombosis, with an important pathophysiological role of auto-antibodies directed against β 2 -GPI., Methods: (Unfolded) VWF levels were studied in normal controls (n=93), APS patients (n=64), non-APS thrombosis patients (n=39) and non-APS auto-immune disease (AID) patients (n=49., Results: Unfolded VWF levels were respectively, 53%, 50% and 36% higher in APS patients, non-APS thrombosis patients and AID patients, compared to normal controls (p<0.0001). Unfolded VWF levels above the 90 th percentile in normal controls were associated with an odds of APS (OR: 8.51; CI:3.26 - 22.2; p<0.001), compared to ORs of non-APS thrombosis (OR:5.87; CI:2.07 - 16.7, p=0.001) and AID (OR:3.71; CI:1.40 - 9.87; p=0.009)., Discussion: We found that APS patients have high levels of unfolded VWF in their circulation. In APS, auto-antibodies against-β2-GPI may interfere with the β2-GPI-mediated inhibition of VWF-platelet interaction. Therefore, the higher unfolded VWF levels in APS could in part explain the association of APS and thrombotic complications., Competing Interests: SH, RL-K, MN, and BL are employees of Synapse Research Institute, part of Diagnostica SAS. BL is an employee of Diagnostica Stago. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 de Laat-Kremers, Huang, ten Cate, Ninivaggi, de Laat and Devreese.)

Background: Patients with ischemic stroke at a young age (18-50 years) have an increased long-term risk of recurrent ischemic events. Hypercoagulability may contribute to this high risk., Objectives: To investigate the associations between in vivo and ex vivo hemostatic parameters and recurrent ischemic events after an ischemic stroke or transient ischemic attack (TIA) at a young age., Methods: We included patients with ischemic stroke or TIA between 1980 and 2010 from the prospective FUTURE cohort. Blood samples were collected in 2010, and patients were followed for recurrent ischemic events from 2010 to 2023. Pro- and anticoagulant markers and thrombin generation assay were measured. Thrombin dynamic analysis was used to study underlying pro- and anticoagulant processes. Hazard ratios (HRs) per standard deviation increase were assessed with cause-specific hazard models., Results: Of the initial cohort of 581 patients, 332 were eligible. The median time between the index event and 2010 was 7.6 years. During a mean follow-up of 6.5 years, 70 of 332 (21.1%) patients experienced a recurrent ischemic event. Lower antithrombin levels (adjusted HR, 0.77; 95% CI, 0.60-0.98) and higher fibrinogen levels (HR, 1.35; 95% CI, 1.04-1.73) were associated with higher risk of recurrent ischemic events. Plasma thrombin generation was not associated with recurrence. However, the thrombin decay constant (HR, 0.67; 95% CI, 0.51-0.87) was associated with a lower risk of recurrent ischemic events., Conclusion: After an ischemic stroke or TIA at a young age, the thrombin decay constant, which reflects reduced protection against thrombin (low antithrombin) and decreased potential to inhibit thrombin (high fibrinogen), is associated with recurrent ischemic events., Competing Interests: Declaration of competing interests J.P.S., R.d.L.-K., M.R., and B.d.L. are employees of Synapse Research Institute, part of the Stago Diagnostica Group. Synapse Research Institute provided financial support for the coagulation assays and salary costs of one PhD candidate (J.P.S.) under joint supervision of the senior researchers of the department of Neurology (F.E.d.L.) and Internal medicine, section vascular medicine, at Radboud university medical center Nijmegen (J.L., S.M.). The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: The mechanism by which combined oral contraceptives (COCs) lead to hypercoagulation is not fully understood, although activated protein C (APC) pathway resistance has been implicated. APC and thrombomodulin (TM) tend to be considered as interchangeable reagents, even though their biological action in coagulation is different. However, it remains unclear which reagent is better suited for the detection of APC pathway resistance. We compared the effectiveness of TM and APC in TG to detect COC-induced APC pathway resistance using thrombin generation (TG)., Methods: TG was measured on ST Genesia in 48 healthy women, of whom 24 used COCs. TG was triggered with STG-ThromboScreen (with and without TM), spiked with a low and high concentration of TM or APC (2 or 15 nM TM, or 1.5 or 5.5 nM APC), aimed to achieve 50% and 90% ETP inhibition, respectively., Results: TG was higher in women using COCs. TM and APC inhibit TG in all women, although their inhibitory effect is more pronounced in women without COC compared to women with COC. The addition of 2 nM TM causes an ETP reduction of 40% (1,289 vs. 768 nM•min) in women without COC and an ETP reduction of 24% (1,704 vs. 1,287 nM•min) in women with COC. The addition of 1.5 nM APC causes an ETP reduction of 41% (1,289 vs. 759 nM•min) in women without COC and an ETP reduction of 23% (1,704 vs. 1,316 nM•min) in women with COC. The difference in effect between women with and without COC is largest when 15 nM TM, aimed at 90% ETP inhibition, is used. 15 nM TM leads to the smallest overlap in ETP inhibition between women with and without COC (27% overlap), compared to 2 nM TM (41% overlap), and 1.5 nM APC (38% overlap) and 5.5 nM APC (41% overlap)., Conclusion: Although TM and APC are often used interchangeably to assess the sensitivity of the APC system in TG, our findings suggest that TM is a better discriminator to detect COC-use induced APC pathway resistance. In addition, we found that the ETP is a better TG test readout for APC pathway resistance testing than the peak height., Competing Interests: MN, LS, RdLK, and BdL are employees of Synapse Research Institute, part of Diagnostica Stago SAS. BdL is an employee of Diagnostica Stago. The remaining author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2024 Ninivaggi, Sokolova, Donkervoort, de Laat and de Laat-Kremers.)

Background: Thrombin 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., Objectives: We investigated the association between TG and mortality in the prospective Moli-sani cohort (n = 21 920)., Methods: TG 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)., Results: LT 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 (ETP Q1 ) 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 ETP Q1 and TTP/LT Q1 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])., Conclusion: Low ETP and TTP/LT ratios are independent risk factors for all-cause mortality in the general population., Competing Interests: Declaration of competing interests R.d.L.K., M.R., D.H., M.N., and B.d.L. are employees of Synapse Research Institute, part of Diagnostica Stago SAS. S.C., A. De Curtis, A. Di Castelnuovo, C.C., M.B.D., and L.I. have no conflict of interest to disclose., (Copyright © 2024 International Society on Thrombosis and Haemostasis. Published by Elsevier Inc. All rights reserved.)

Background: α 2 -macroglobulin (α 2 M) is a versatile endopeptidase inhibitor that plays a role in cell growth, inflammation and coagulation. α 2 M is an inhibitor of key coagulation enzyme thrombin. Hypercoagulability due to an excess of thrombin production can cause thrombotic events. Therefore, we investigated the association of α 2 M levels and cardiovascular events in a subset of the general Italian population., Methods: We determined α 2 M levels in the baseline samples of a prospective cohort (n = 19,688; age: 55 ± 12 years; 47.8 % men) of the Moli-sani study and investigated the association with the cardiovascular events (n = 432, 2.2 %) in the median follow-up period of 4.3 years. Hazard ratios (HR) with 95 % confidence intervals (CI) were calculated by multivariable Cox regression and adjusted for a large panel of confounding factors., Results: α 2 M levels above the 90th percentile were significantly associated with cardiovascular disease (CVD) events after full adjustment for age, sex, current smoking, BMI, oral contraceptive use, cardiovascular diseases, hypertension, hypercholesterolemia, diabetes and history of cancer (HR: 1.36; CI: 1.06-1.74). Moreover, high α 2 M was associated with coronary heart disease (CHD; HR: 1.47; CI: 1.12-1.91), but not stroke. Stratification for CVD at baseline showed that high α 2 M levels are associated with CHD events in subjects without CVD at baseline (HR: 1.40; CI: 1.00-1.95) and subjects with CVD at baseline (HR: 1.58; CI: 1.02-2.44)., Conclusion: We show in a prospective cohort that high levels of α 2 M could be a risk factor for cardiovascular events, especially coronary heart disease events., Competing Interests: Declaration of competing interest RdLK, QY, and BdL are employees of Synapse Research Institute, part of Diagnostica Stago SAS. The other authors declare no competing interests., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

There is ongoing debate as to whether abacavir (ABC) increases the risk for cardiovascular disease(CVD) in people living with HIV (PLHIV) and the mechanisms underlying this possible association. We recently showed that the use of an ABC-containing regimen was independently associated with increased thrombin generation (TG). In the present study, we aim to explore these findings further, by studying the mechanistical processes that underly the global thrombin generation test via thrombin dynamics analysis. Thrombin dynamics analysis can pinpoint the cause of increased thrombin generation associated with ABC-use either to the procoagulant prothrombin conversion pathway or the anticoagulant thrombin inactivation pathway. In this cross-sectional study, 208 virally suppressed PLHIV were included, of whom 94 were on a ABC-containing regimen, 92 on a tenofovir disoproxil fumarate (TDF)-containing regimen, and the remainder on other regimens. We used Calibrated Automated Thrombinography to measure thrombin generation and perform thrombin dynamics analysis. The total amount of prothrombin conversion, as well as the maximum rate of prothrombin conversion were significantly increased in PLHIV on an ABC containing regimen compared to other treatment regimens. The levels of pro- and anticoagulant factors were comparable, indicating that the ABC-induced changes affect the kinetics of prothrombin conversion rather than procoagulant factor levels. Moreover, Von Willebrand Factor (VWF), active VWF and VWF pro-peptide levels were significantly higher in PLHIV than controls without HIV. However, they did not differ between ABC and non-ABC treated participants., Competing Interests: QY, SH, RL-K, MN, and BL are employees of Synapse Research Institute, part of Diagnostica Stago SAS. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Yan, Huang, van der Heijden, Ninivaggi, van de Wijer, de Laat-Kremers, Van der Ven, de Laat and de Mast.)

Thrombosis is a major clinical complication of COVID-19 infection. COVID-19 patients show changes in coagulation factors that indicate an important role for the coagulation system in the pathogenesis of COVID-19. However, the multifactorial nature of thrombosis complicates the prediction of thrombotic events based on a single hemostatic variable. We developed and validated a neural net for the prediction of COVID-19-related thrombosis. The neural net was developed based on the hemostatic and general (laboratory) variables of 149 confirmed COVID-19 patients from two cohorts: at the time of hospital admission (cohort 1 including 133 patients) and at ICU admission (cohort 2 including 16 patients). Twenty-six patients suffered from thrombosis during their hospital stay: 19 patients in cohort 1 and 7 patients in cohort 2. The neural net predicts COVID-19 related thrombosis based on C-reactive protein (relative importance 14%), sex (10%), thrombin generation (TG) time-to-tail (10%), α 2 -Macroglobulin (9%), TG curve width (9%), thrombin-α 2 -Macroglobulin complexes (9%), plasmin generation lag time (8%), serum IgM (8%), TG lag time (7%), TG time-to-peak (7%), thrombin-antithrombin complexes (5%), and age (5%). This neural net can predict COVID-19-thrombosis at the time of hospital admission with a positive predictive value of 98%-100%., Competing Interests: RL-K, MN, and BL declare no competing interests and are employees of Synapse Research Institute, part of Diagnostica Stago S.A.S. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 de Laat-Kremers, De Jongh, Ninivaggi, Fiolet, Fijnheer, Remijn and de Laat.)

Thrombin generation (TG) is known as a physiological approach to assess the hemostatic function. Although it correlates well with thrombosis and bleeding, in the current setup it is not sensitive to the effects of fluctuations in single coagulation factors. We optimized the calibrated automated thrombinography (CAT) method to quantify FII, FV and FX activity within the coagulation system. The CAT assay was fine-tuned for the assessment of FII, FV and FX by diluting the samples in FII-, FV-, or FX-deficient plasma, respectively, and measuring TG. Plasma FII levels correlated linearly with the ETP up to a plasma concentration of 100% FII. FV and FX levels correlated linearly with the peak height up to a plasma level of 2.5% FV and 10% FX, respectively. Sensitized CAT protocols were designed by adding a fixed volume of a pre-diluted patient sample to FII, FV, and FX deficient plasma in TG experiments. This approach makes the TG measurement dependent on the activity of the respective coagulation factor. The ETP or peak height were quantified as readouts for the coagulation factor activity. The intra- and inter-assay variation coefficients varied from 5.0 to 8.6%, and from 3.5 to 5.9%, respectively. Reference values were determined in 120 healthy subjects and the assays were clinically validated in 60 patients undergoing coronary artery bypass grafting (CABG). The sensitized CAT assays revealed that the contribution of FII, FV, and FX to the TG process was reduced after CABG surgery, leading to reduced prothrombin conversion and subsequently, lower TG., Competing Interests: CB, JK, MN, RL-K, and BL are employees of Synapse Research Institute. The remaining author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Bai, Konings, Ninivaggi, Lancé, de Laat and de Laat-Kremers.)

Background: Thrombosis is common in subjects suffering from cardiovascular diseases (CVD) and cancer. Hypercoagulation plays a pivotal role in the pathophysiology of thrombosis. Therefore, the inactivation of thrombin, the key enzyme in coagulation, is tightly regulated via antithrombin (AT). AT deficiency is related to thrombosis and cardiovascular death. In this study we investigated the association between AT levels and mortality, in particularly cardiovascular-related and cancer-related death in the general population., Methods: We studied the association of AT levels and mortality in a prospective cohort sampled from the general Italian population (n = 19,676). AT levels were measured in the baseline samples, and mortality was recorded during a median follow-up period of 8.2 years. Cox regression was performed to investigate the association of all-cause, CVD-related and cancer-related mortality with variations in AT levels., Results: In total, 989 subjects died during follow-up, of which 373 subjects of CVD and 353 of cancer-related causes. Cox analysis revealed that, after adjustment for age, sex, current smoking, BMI, diabetes, hypertension, hypercholesterolemia, history of cardiovascular disease, history of cancer, vitamin K antagonists, antiplatelet medication, heparin and oral contraceptives AT levels were not associated with all-cause mortality (HRQ1vsQ5: 0.92, 95% CI:0.74-1.15). Interestingly, the risk of CVD-related mortality was reduced in subjects with low AT levels compared to subjects with higher AT levels, after adjustment for age and sex and other confounders did not change the association (HRQ1vsQ5: 0.64, 95% CI:0.44-0.91). Moreover, low AT levels were associated with increased cancer mortality in a fully adjusted model (HRQ1vsQ2-5: 1.26, 95% CI:0.88-1.81)., Conclusions: Low AT levels are associated to a lower risk of fatal cardiovascular events in the general population, regardless of age, sex and medication use. In contrast, low AT levels are associated with lower cancer survival. For the first time we show that AT levels lower than the normal range in the general population, even before the development or diagnosis of cancer, are associated with an elevated risk of cancer death., Competing Interests: RdLK, QY, LvdV, MN and BdL are employees of Synapse Research Institute, part of Diagnostica Stago SAS. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Various vaccines were developed to reduce the spread of the Severe Acute Respiratory Syndrome Cov-2 (SARS-CoV-2) virus. Quickly after the start of vaccination, reports emerged that anti-SARS-CoV-2 vaccines, including ChAdOx1-S, could be associated with an increased risk of thrombosis. We investigated the hemostatic changes after ChAdOx1-S vaccination in 631 health care workers. Blood samples were collected 32 days on average after the second ChAdOx1-S vaccination, to evaluate hemostatic markers such as D-dimer, fibrinogen, α2-macroglobulin, FVIII and thrombin generation. Endothelial function was assessed by measuring Von Willebrand Factor (VWF) and active VWF. IL-6 and IL-10 were measured to study the activation of the immune system. Additionally, SARS-CoV-2 anti-nucleoside and anti-spike protein antibody titers were determined. Prothrombin and fibrinogen levels were significantly reduced after vaccination (-7.5% and -16.9%, p < 0.0001). Significantly more vaccinated subjects were outside the normal range compared to controls for prothrombin (42.1% vs. 26.4%, p = 0.026) and antithrombin (23.9% vs. 3.6%, p = 0.0010). Thrombin generation indicated a more procoagulant profile, characterized by a significantly shortened lag time (-11.3%, p < 0.0001) and time-to-peak (-13.0% and p < 0.0001) and an increased peak height (32.6%, p = 0.0015) in vaccinated subjects compared to unvaccinated controls. Increased VWF (+39.5%, p < 0.0001) and active VWF levels (+24.1 %, p < 0.0001) pointed toward endothelial activation, and IL-10 levels were significantly increased (9.29 pg/mL vs. 2.43 pg/mL, p = 0.032). The persistent increase of IL-10 indicates that the immune system remains active after ChAdOx1-S vaccination. This could trigger a pathophysiological mechanism causing an increased thrombin generation profile and vascular endothelial activation, which could subsequently result in and increased risk of thrombotic events., Competing Interests: BL, RdL-K, MR, DH, and MN are employees of Synapse Research Institute, part of Diagnostica Stago. HC received funding for research from Bayer and Pfizer; compensation fees for consultancy and advisory boards from Daaichi, Pfizer, Leo, Bayer, Galapagos, Anthos, Alexion, and Alveron; shareholder from Coagulation profile; all benefits were transferred to the CARIM institute to support investigator-initiated research. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 de Laat, Stragier, de Laat-Kremers, Ninivaggi, Mesotten, Thiessen, Van Pelt, Roest, Penders, Vanelderen, Huskens, De Jongh, Laenen, Fivez, ten Cate, Heylen, Heylen and Steensels.)

Background: The haemostatic balance is an equilibrium of pro- and anticoagulant factors that work synergistically to prevent bleeding and thrombosis. As thrombin is the central enzyme in the coagulation pathway, it is desirable to measure thrombin generation (TG) in order to detect possible bleeding or thrombotic phenotypes, as well as to investigate the capacity of drugs affecting the formation of thrombin. By investigating the underlying processes of TG (i.e., prothrombin conversion and inactivation), additional information is collected about the dynamics of thrombin formation., Objectives: To obtain reference values for thrombin dynamics (TD) analysis in 112 healthy donors using an automated system for TG., Methods: TG was measured on the ST Genesia, fibrinogen on the Start, anti-thrombin (AT) on the STA R Max and α 2 Macroglobulin (α 2 M) with an in-house chromogenic assay., Results: TG was measured using STG-BleedScreen, STG-ThromboScreen and STG-DrugScreen. The TG data was used as an input for TD analysis, in combination with plasma levels of AT, α 2 M and fibrinogen that were 113% (108-118%), 2.6 μM (2.2 μM-3.1 μM) and 2.9 g/L (2.6-3.2 g/L), respectively. The maximum rate of the prothrombinase complex (PCmax) and the total amount of prothrombin converted (PCtot) increased with increasing tissue factor (TF) concentration. PC tot increased from 902 to 988 nM, whereas PC max increased from 172 to 508 nM/min. Thrombin (T)-AT and T-α 2 M complexes also increased with increasing TF concentration (i.e., from 860 to 955 nM and from 28 to 33 nm, respectively). PC tot , T-AT and T-α 2 M complex formation were strongly inhibited by addition of thrombomodulin (-44%, -43%, and -48%, respectively), whereas PC max was affected less (-24%). PC tot , PC max , T-AT, and T-α 2 M were higher in women using oral contraceptives (OC) compared to men/women without OC, and inhibition by thrombomodulin was also significantly less in women on OC ( p < 0.05)., Conclusions: TG measured on the ST Genesia can be used as an input for TD analysis. The data obtained can be used as reference values for future clinical studies as the balance between prothrombin conversion and thrombin inactivation has shown to be useful in several clinical settings., Competing Interests: AC is full-time employee of Diagnostica Stago S.A.S. QY, MN, RD, and BD are employees of Synapse Research Institute, part of Diagnostica Stago S.A.S. The remaining author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Carlo, Yan, Ten Cate, De Laat-Kremers, De Laat and Ninivaggi.)

The coagulation system can be assessed by the thrombin generation (TG) assay, and increased TG peak height, endogenous thrombin potential (ETP), and velocity index are associated with an increased risk of thrombosis. Obesity had been reported to increase TG and is associated with dyslipidemia, which also predisposes to atherosclerotic cardiovascular disease (CVD). However, the effect of the blood lipid profile on TG has not been studied extensively. To gain more insight into the associations of TG, body mass index (BMI) and lipid profile, we studied TG in relation to these parameters in a large Italian population cohort, the Moli-sani study ( N = 22,546; age ≥ 35 years; 48% men). TG was measured in plasma samples collected at the enrollment of subjects in the Moli-sani study. TG was triggered with 1 or 5 pM tissue factor, and TG parameters lag time, peak, ETP, time-to-peak (TTP) and velocity index (VI). Additionally, thrombomodulin was added to assess the function of the activated protein C system during TG. In both women and men, overweight (BMI 25-30 kg/m 2 ) and obesity (BMI > 30 kg/m 2 ) were significantly associated with higher ETP, peak and VI (all p < 0.001). High total cholesterol, triglycerides and LDL-cholesterol levels were significantly associated with increased ETP and peak (all p < 0.001). Linear regression analysis revealed that the ETP is positively associated with both plasma LDL and HDL cholesterol levels, whereas the velocity index is positively associated with HDL cholesterol. Additionally, ETP, peak and VI were significantly associated with the plasma triglycerides content. In conclusion, our study shows significant associations of high BMI and blood lipid levels with increased TG parameters, and this hypercoagulability may partly explain the increased risk of CVD in individuals with obesity and/or dyslipidemia., Competing Interests: Synapse Research Institute is a non-for-profit organization, member of Diagnostica Stago SAS. RdLK, LvdV, MN, DH, CB, DY, and BdL are employees of Synapse Research Institute. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 de Laat-Kremers, Di Castelnuovo, van der Vorm, Costanzo, Ninivaggi, Cerletti, Huskens, De Curtis, Gialluisi, Bai, de Gaetano, Yin, Donati, de Laat, Iacoviello and the Moli-sani Investigators.)

Thrombin generation (TG) assay is an overall assay to assess the functionality of the hemostatic system and may be a useful tool in diagnosing patients with hyper- and hypocoagulability. Lack of standardization in performing the assays contributes largely to poor correlation between assays and study results. The current lack of standardization remains a major issue in the setting of TG, as illustrated in a recent survey of the ISTH/SSC indicating differences in pre-, analytical, and post-analytical factors among users. These factors may considerably affect the between-laboratory reproducibility of results. Based on the results of the survey and a current review of the literature, along with insights and strong consensus of key investigators in the field, we present guidance for measurement of TG in a clinical setting. Recommendations on blood drawing, handling, processing, and sample storage; reagent concentration and source; analytical conditions on dilution of samples and temperature; calibration and replicate testing; calculation and interpretation of results; and reference values are addressed to help in reducing interlaboratory variation. These recommendations aim at harmonization between methods and laboratories to support the application of TG in patient diagnosis and management., (© 2021 International Society on Thrombosis and Haemostasis.)

Background: Fluorogenic thrombin generation (TG) assays are commonly used to determine global coagulation phenotype in plasma. Whole blood (WB)-TG assays reach one step closer to physiology by involving the intrinsic blood cells, but erythrocytes cause variable quenching of the fluorescence signals, hampering its routine application., Objective: To develop a new assay for continuous WB-TG measurement., Methods: In the new WB-TG assay, the erythrocyte-caused distortion of signal was solved by continuously mixing the sample during the measurement. The assay was validated by evaluating the reproducibility and comparing with the paper-based WB-TG assay. Reconstituted human blood and WB from 119 healthy donors was tested to explore the influences of hematocrit and platelet count on TG., Results: This novel WB-TG assay showed good reproducibility while being less affected by contact activation compared with the previous paper-based assay. Reconstitution experiments showed that the lag time of TG was shortened by the addition of platelets but not erythrocytes. Increasing hematocrit strongly augmented the peak thrombin, even in the presence of high platelet counts. The lag time and peak of WB-TG of 119 healthy donors were positively related to erythrocyte count after adjusting for age, sex, and oral contraceptive use with multiple linear regression analyses. The reference range and interindividual variation of WB-TG were determined in the healthy cohort., Conclusions: A novel WB-TG assay was developed, which is a straightforward tool to measure the involvement of platelets and erythrocytes in TG and may assist the research of blood cell-associated coagulation disorders., (© 2020 Universiteit Maastricht. Journal of Thrombosis and Haemostasis published by Wiley Periodicals, Inc. on behalf of International Society on Thrombosis and Haemostasis.)

Introduction: Changes in the coagulation profile in children with liver disease and extrahepatic portal vein obstruction or shunt result in both bleeding and thrombosis. Routine coagulation tests do not accurately predict bleeding risk, as they are not sensitive to changes in anticoagulant factors. The thrombin generation assay could be suitable for describing the overall balance of coagulation in children with liver disease. This study aims to characterise the mechanism of thrombin generation in this population, focusing on prothrombin conversion and thrombin inhibition., Methods: Patients were categorised as: severe (paediatric end stage liver disease score > 15) and mild disease, or portal vein obstruction or shunt. Age and gender matched healthy controls were used. The thrombin generation assay was performed in plasma samples from patients and controls with and without exogenous thrombomodulin and the results were further analysed with the computational thrombin dynamics method., Results: A total of 42 patients (severe, n = 5; mild, n = 29, obstruction/shunt, n = 8) and 20 controls were included in this study. The total prothrombin conversion, thrombin-antithrombin formation and the thrombin decay capacity, in the presence and absence of thrombomodulin were reduced in children with severe liver disease. The rate of prothrombin conversion was increased and thrombin decay capacity was decreased in patients with portal vein obstruction or shunt compared to controls., Conclusion: This study demonstrates changes in the mechanism in thrombin generation seen in severe chronic liver disease. The changes vary in parenchymal versus non parenchymal liver disease and further study assessing the clinical significance of these variations in mechanism is required., Competing Interests: Declaration of competing interest None to declare., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Introduction: Calibrated automated thrombinography (CAT) is a sensitive method to assess coagulation. Dabigatran inhibits both free thrombin and the α 2 macroglobulin (α 2 M)-thrombin complex, which results in an erroneously increased peak and endogenous thrombin potential (ETP) without affecting lag time and time-to-peak. The aim of this study was to elucidate the artefacts in CAT when dabigatran is present., Materials and Methods: Thrombin generation (TG) was measured in vitro by using CAT in the presence or absence of 6 μM idarucizumab in plasma spiked with dabigatran. Additionally, ex vivo measurements were performed in plasmas of 63 patients using dabigatran in the presence and absence of idarucizumab., Results: The in vitro experiments confirmed that the ETP, peak and velocity index were artificially increased. This was mainly due to the inhibition of the calibrator by dabigatran and partly due to CAT algorithms. The calibration artefact could be resolved by adding idarucizumab to the calibrator well. However, the second, mathematical artefact remains when dabigatran is present in the TG well. These findings were corroborated by ex vivo experiments i.e. the lag time and time-to-peak were significantly reduced in patients upon addition of idarucizumab, but the ETP and peak were not significantly affected. The velocity index did change significantly, since this is a combination of time-dependent factors and the peak., Conclusions: The peak, ETP and velocity index do not represent the anticoagulant effect of dabigatran on TG measured with CAT. The lag time and time-to-peak, however, do reflect the effect of dabigatran., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Background: Recently, we have reported that asthma is characterized by prothrombotic blood alterations, which were related to the low-grade inflammatory state. Inflammation, however, may also lead to vascular dysfunction. The aim of this study was to evaluate plasma levels of cellular fibronectin (cFN), a marker of vascular injury in asthmatics, and to analyze their impact on described previously prothrombotic blood alterations., Methods: In a cross-sectional study, we investigated 164 adult stable asthmatics and 72 matched controls. Plasma cFN was measured using an ELISA. Its relations to inflammation, thrombin generation, fibrinolytic capacity, expressed as clot lysis time (CLT), and platelet markers were evaluated., Results: Asthma was associated with 50.1% higher plasma cFN levels as compared with controls (p < 0.001, after adjustment for potential confounders). There was a positive association of cFN with asthma severity and inverse with the FEV 1 /VC index (β = 0.2 [95%CI:0.13-0.28] and β = -0.15 [95%CI: -0.23 to -0.07], respectively). In asthmatics cFN positively correlated with high-sensitivity C-reactive protein (β = 0.24 [95%CI:0.16-0.32]), fibrinogen (β = 0.13 [95%CI:0.04-0.21]), interleukin-6 (β = 0.23 [95%CI:0.15-0.3]), platelet factor 4 (β = 0.14 [95%CI:0.06-0.21]), plasminogen (β = 0.11 [95%CI:0.04-0.19]) and CLT (β = 0.35 [95%CI:0.28-0.42]). In both groups cFN was related to the endogenous thrombin potential (ETP) (β = 0.51 [95%CI:0.44-0.57], and β = 0.17 [95%CI:0.07-0.27], respectively). Multiple regression models showed that cFN was the most potent independent predictor of both ETP and CLT in asthmatics., Conclusion: Presented study is the first to show increased plasma cellular fibronectin in asthma, which is associated with disease severity, inflammation, and prothrombotic blood alterations. This novel observation suggests a previously unknown modulator of prothrombotic plasma properties in asthmatics., (Copyright © 2018 Elsevier Ltd. All rights reserved.)