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.

Comprehensive investigation of platelet function in patients with cirrhosis

Cirrhosis presents with thrombocytopenia and possibly thrombocytopathy. Previous studies exploring platelet function gave conflicting results and most controversies are explained by the variety of methods employed for investigation. We sought to assess in-vitro the overall platelet function in cirrhosis. We investigated 34 patients by using the following tests. (i)Aggregometry. (ii)Measurement of the content of platelet granules. (iii)Cytometric platelet activation. (iv)Plasmatic markers of in-vivo platelet activation. (v)Platelet procoagulant activity by thrombin generation (TG) in platelet-rich plasma (PRP). TG measured in PRP for patients and controls was similar. Platelets from patients with cirrhosis showed reduction of aggregation and secretion of ATP. Similar results were observed for platelet activation parameters such as P-selectin expression and PAC-1 platelet binding. Plasma levels of βeta-thromboglobulin and soluble P-selectin, were increased in patients-vs-controls. In contrast, there were no patients-vs-controls differences for plasmatic platelet-factor-4. Results are consistent with a state of in-vivo platelet activation and decreased in-vitro aggregation. Since bleeding events following invasive procedures are uncommon in cirrhosis, we speculate that in-vitro aggregometry testing does not reflect the situation occurring in-vivo. Results of the study and pathophysiological considerations support the conclusion that platelet function in cirrhosis as determined by aggregometry, although somewhat impaired, may support the overall hemostatic potential, which is needed for most invasive interventions. These conclusions are in line with the recommendations of international guidelines, warning against indiscriminate use of prophylactic preprocedural administration of platelets before invasive procedures. Decision on platelet support should not be made based on in-vitro laboratory testing for platelet function.

Impact of therapeutic plasma exchange on intact protein S, apolipoproteins, and thrombin generation

INTRODUCTION

Therapeutic plasma exchange (TPE), with solvent/detergent (S/D)-treated plasma as replacement fluid, is an extracorporeal blood purification technique with major impact on both coagulation and lipids. Our previous in vitro study showed that S/D-plasma enhances thrombin generation by lowering intact protein S (PS) levels.

AIMS

To evaluate the impact of altered lipid balance on coagulation phenotype during heparin-anticoagulated TPE with S/D-plasma, and to investigate whether the lowered intact PS levels with concomitant procoagulant phenotype, are recapitulated in vivo.

METHODS

Coagulation biomarkers, thrombin generation with Calibrated Automated Thrombogram (CAT), and lipid levels were measured before and after the consecutive 1st, 3rd and 5th episodes of TPE performed to six patients with Guillain-Barré syndrome or myasthenia gravis. The effects of in vitro dilution of S/D-plasma on thrombin generation were explored with CAT to mimic TPE.

RESULTS

Patients did not have coagulation disorders, except elevated FVIII. Intact PS, lipoproteins, especially LDL, Apolipoprotein CIII (ApoC3) and ApoB/ApoA1 ratio declined (p < 0.05). In contrast, VLDL and triglyceride levels stayed intact. CAT lag time shortened (p < 0.05). In vitro dilution of S/D plasma with co-transfused Ringer's lactate and 4% albumin partially reduced its procoagulant phenotype in CAT, which is mainly seen as peak thrombin, and modestly shortened lag time.

CONCLUSIONS

After the five settings of TPE using S/D-plasma in vivo, which associated with heparinization and reduced coagulation factor activities, our observations of declining natural anticoagulant intact PS and apolipoproteins refer to rebalance of the hemostatic and lipid profiles.

Reduced fibrin clot permeability on admission and elevated E-selectin at 3 months as novel risk factors of residual pulmonary vascular obstruction in patients with acute pulmonary embolism

BACKGROUND

Residual pulmonary vascular obstruction (RPVO) is common following pulmonary embolism (PE) but its association with fibrin clot properties is poorly understood. We investigated whether prothrombotic state and hypofibrinolysis markers can identify patients with RPVO.

METHODS

In 79 normotensive noncancer patients (aged 56 ± 13.3 years) with acute PE, we determined fibrin clot permeability (Ks), clot lysis time (CLT), endogenous thrombin potential (ETP), fibrinolysis proteins, oxidative stress markers, and E-selectin on admission before initiation of anticoagulant therapy, after 5-7 days, and 3 months of anticoagulation. RPVO was diagnosed using computed tomography angiography 3-6 months since PE.

RESULTS

Patients with RPVO (n = 23, 29.1%) had at baseline higher simplified Pulmonary Embolism Severity Index (sPESI) (P = 0.004), higher N-terminal brain natriuretic propeptide (P = 0.006) and higher D-dimer (P = 0.044). Patients with versus without RPVO had lower Ks (P < 0.001) and longer CLT (P < 0.05), both at baseline and 5-7 days since admission, but not at 3 months. Patients with RPVO showed 40.6% higher E-selectin (P < 0.001) solely at 3 months. By multivariable logistic regression, baseline Ks (odds ratio [OR] 0.010, 95% confidence interval [CI] 0.001-0.837, P = 0.042, per 10- 9 cm2), baseline D-dimer (OR 1.105, 95% CI 1.000-1.221, P = 0.049, per 100 ng/ml), and E-selectin levels after 3 months (OR 3.874, 95% CI 1.239-12.116, P = 0.020, per 1 ng/ml) were associated with RPVO.

CONCLUSIONS

RPVO patients despite anticoagulation characterize with the formation of denser fibrin clots on admission and higher E-selectin at 3 months. Those parameters could be the potential novel RPVO risk factors that warrant further evaluation in an independent cohort.

Exercise and hypoxia-induced hypercoagulability is counterbalanced in women in part by decreased platelet reactivity

Hypoxia plays an important role in several pathologies, e.g. chronic obstructive pulmonary disease and obstructive sleep apnea syndrome, and is linked to an increased thrombosis risk. Furthermore, oxygen deprivation is associated with hypercoagulability. In this study, we investigated the effect of gender and exercise on the coagulation potential under hypoxic conditions at high altitude by assessing thrombin generation (TG) and platelet activation. Hereto, ten healthy volunteers were included (50 % male, median age of 27.5 years). The measurements were conducted first at sea level and then twice at high altitude (3883 m), first after a passive ascent by cable car and second after an active ascent by a mountain hike. As expected, both the passive and active ascent resulted in a decreased oxygen saturation and an increased heart rate at high altitude. Acute mountain sickness symptoms were observed independently of the ascent method. After the active ascent, platelet, white blood cell and granulocyte count were increased, and lymphocytes were decreased, without a gender-related difference. FVIII and von Willebrand factor were significantly increased after the active ascent for both men and women. Platelet activation was reduced and delayed under hypobaric conditions, especially in women. TG analysis showed a prothrombotic trend at high altitude, especially after the active ascent. Women had a hypercoagulable phenotype, compared to men at all 3 timepoints, indicated by a higher peak height and endogenous thrombin potential (ETP), and shorter lag time and time-to-peak. In addition, ETP and peak inhibition by thrombomodulin was lower in women after the active ascent, compared to men. Interestingly, data normalisation for subject baseline values indicated an opposing effect of altitude-induced hypoxia on α2-macroglobulin levels and TG lag time between men and women, decreasing in men and increasing in women. We conclude that hypoxia increases TG, as well as FVIII and VWF levels in combination with exercise. In contrast, platelets lose their responsiveness at high altitude, which is most pronounced after heavy exercise. Women had a more pronounced prothrombotic phenotype compared to men, which we theorize is counterbalanced under hypobaric conditions by decreased platelet activation.

Anticoagulant effects of protein C, protein S, and antithrombin levels on the protein C pathway in young children

The protein C (PC) pathway involves physiological anticoagulant factors (PC, protein S [PS], and factor V) and performs major anticoagulant functions in adults. Variations in overall PC pathway function due to dynamic changes in PC and PS in early childhood are poorly understood. We aimed to evaluate the contributions of PC pathway function during early childhood by measuring changes in plasma thrombin generation (TG) after administration of the PC activator protac. We evaluated correlations between anticoagulant factors and percentage of protac-induced coagulation inhibition (PiCi%). Before protac addition, TG in newborns (n = 35), infants (n = 42), young children (n = 35), and adults (n = 20) were 525 ± 74, 720 ± 96, 785 ± 53, and 802 ± 64 mOD/min, and PiCi% were 42.1 ± 9.9, 69.8 ± 11.0, 82.9 ± 4.4, and 86.9 ± 3.4%, respectively. The distribution of PiCi% on the two axes of TG (with or without protac) changed continuously with age and differed from that of warfarin-treated plasma and adult PC- or PS-deficient plasma. PiCi% increased dynamically during infancy and correlated with PS levels in newborns and PC levels in young children. Addition of PC or fresh frozen plasma equivalent to approximately 25% PC to PC-deficient plasma improved PiCi%. This automatic measurement requires only a small sample volume and is useful for analysis of developmental hemostasis.

Thrombin generation and all-cause mortality in The Brazilian Longitudinal Study of Adult Health (ELSA-Brasil)

INTRODUCTION

Thrombin generation assay (TGA) is a laboratory method that provides the global evaluation of hemostasis. The association between thrombin generation and all-cause mortality is poorly investigated and results are contradictory. This study evaluated whether TGA parameters are associated with all-cause mortality in a prospective cohort.

METHODS

This study was conducted in 2,588 participants enrolled at baseline of the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil). TGA was performed using the Calibrated Automated Thrombogram (CAT) method, and its parameters lagtime, time-to-peak, peak, Endogenous Thrombin Potential (ETP) and normalized ETP (nETP) were evaluated according to the reference interval (RI). The association between TGA parameters and all-cause mortality was estimated by Cox regression and adjusted for confounders.

RESULTS

The mean follow-up time was 6.6 ± 2.7 years and 85 deaths occurred. After adjustment, time-to-peak values above the RI at low and high tissue factor (TF) concentrations were associated with higher risk of death [HR = 2.45 (95 % CI: 1.17-5.13) and HR = 2.24 (95 % CI: 1.02-4.93), respectively] and nETP and peak values below RI at high TF concentration were associated with higher risk of death [HR = 3.85 (95 % CI: 1.39-10.68) and HR = 2.56 (95 % CI: 1.17-5.61), respectively].

CONCLUSIONS

Delayed thrombin generation was associated with higher risk of all-cause mortality.

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

INTRODUCTION

Growing 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 METHODS

An 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.

RESULTS

TG/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.

CONCLUSIONS

FXIa reveals new relationships between TG, PG and CFL parameters in factor deficiencies suggesting potential benefits for discrimination of bleeding phenotypes.

Sex Differences in Thrombin Generation in Patients with Acute Ischemic Stroke

Sex differences in stroke exist, including variation in stroke risk and outcome. Differences in thrombin generation may contribute to this variation between females and males. To examine this, we assessed sex differences in thrombin generation between females and males with acute ischemic stroke and the relationship to blood cell gene expression. In 97 patients with acute ischemic stroke, thrombin generation was measured by thrombin generation assay. Blood cell gene expression was measured by microarray. Differences in thrombin generation between sexes were identified and the relationship to blood cell gene expression examined. Genes associated with sex differences in thrombin generation were analyzed by functional pathway analysis. Females and males had similar overall capacity to generate thrombin. The peak thrombin generated in females was 468.8 nM (SD 91.6), comparable to males (479.3nM;SD 90.8; p = 0.58). Lag time, time to peak thrombin, and endogenous thrombin potential were also similar between females and males. While overall thrombin generation was comparable between females and males with stroke, differences in genes that promote this thrombin generation exist. Females with high peak thrombin had an increase in genes that promote thrombosis, and platelet activation. In contrast, males with high peak thrombin had a decrease in genes involved in thrombus degradation. Females and males with acute ischemic stroke have similar capacity to generate thrombin, however, differences may exist in how this thrombin generation is achieved, with females having increased thrombin signaling, and platelet activation, and males having decreased thrombus degradation. This suggests regulatory differences in thrombosis may exist between females and males that may contribute to sex differences in stroke.

Platelets provide robustness of spatial blood coagulation to the variation of initial conditions

Activated platelets provide phospholipid surface and secrete coagulation factors, enhancing blood clotting. We investigated the role of platelets in the regulation of blood coagulation spatial dynamics. We activated blood clotting with tissue factor-bearing (TF) surface in platelet-rich plasma (PRP) or platelet-free plasma (PFP). When blood coagulation was initiated by high TF density, clot growth rate (V) in PRP (2 × 105/μL platelets) was only 15 % greater than in PFP. Spatial distribution of thrombin in PRP had a peak-like shape in the area of the fibrin clot edge, while in PFP thrombin was distributed in the shape of descending plateau. Platelet inhibition with prostaglandin E1 or cytochalasin D made spatial thrombin distribution look like in the case of PFP. Inhibition of blood coagulation by natural endogenous inhibitor heparin was diminished in PRP, while the effect of the exogenous or artificial inhibitors (rivaroxaban, nitrophorin, hirudin) remained undisturbed in the presence of platelets. Ten times decrease of the TF surface density greatly depressed blood coagulation in PFP. In PRP only clotting initiation phase was, while the propagation phase remained intact. Coagulation factor deficiency greatly reduced amount of thrombin and decreased V in PFP rather than in PPR. Thus, platelets were redundant for clotting in normal plasma under physiological conditions but provided robustness of the coagulation system to the changes in initial conditions.

How to assess hypercoagulability in heparin-induced thrombocytopenia? Biomarkers of potential value to support therapeutic intensity of non-heparin anticoagulation

BACKGROUND

In case of heparin-induced thrombocytopenia (HIT), the switch to a non-heparin anticoagulant is mandatory, at a therapeutic dose. Such a treatment has limitations though, especially for patients with renal and/or hepatic failure. Candidate laboratory tests could detect the more coagulable HIT patients, for whom therapeutic anticoagulation would be the more justified.

PATIENTS AND METHODS

This was a monocentre observational prospective study in which 111 patients with suspected HIT were included. Nineteen were diagnosed with HIT (ELISA and platelet activation assay), among whom 10 were classified as HITT + when a thrombotic event was present at diagnosis or during the first following week. Two plasma prethrombotic biomarkers of in vivo activation of the haemostasis system, procoagulant phospholipids (ProcoagPPL) associated with extracellular vesicles and fibrin monomers (FM test), as well as in vitro thrombin potential (ST Genesia; low picomolar tissue factor) after heparin neutralization (heparinase), were studied. The results were primarily compared between HITT + and HITT- patients.

RESULTS

Those HIT + patients with thrombotic events in acute phase or shortly after (referred as HITT+) had a more coagulable phenotype than HIT + patients without thrombotic events since: (i) clotting times related to plasma procoagulant phospholipids tended to be shorter; (ii) fibrin monomers levels were statistically significantly higher (p = 0.0483); (iii) thrombin potential values were statistically significantly higher (p = 0.0404). Of note, among all patients suspected of suffering from HIT, we did not evidence a hypercoagulable phenotype in patients diagnosed with HIT compared to patients for whom the diagnosis of HIT was ruled out.

CONCLUSION

The three tests could help identify those HIT patients the most prone to thrombosis.

Enhanced in vivo and ex vivo thrombin generation after lower-leg trauma, but not after knee arthroscopy

BACKGROUND

There is room for improvement of prevention of venous thromboembolism (VTE) after lower-leg cast application or knee arthroscopy. Information about the mechanism of clot formation in these patients may be useful to identify new prophylaxis targets. We aimed to study the effect of 1) lower-leg injury and 2) knee arthroscopy on thrombin generation.

METHODS

A cross-sectional study was conducted using plasma samples of POT-(K)CAST trials to measure ex vivo thrombin generation (Calibrated Automated Thrombography [CAT]) and plasma levels of prothrombin fragment 1 + 2 (F1 + 2), thrombin-antithrombin (TAT), fibrinopeptide A (FPA). Plasma was obtained shortly after lower-leg trauma or before and after (< 4 h) knee arthroscopy. Participants were randomly selected from those who did not develop VTE. For aim 1, samples of 88 patients with lower-leg injury were compared with 89 control samples (i.e., preoperative samples of arthroscopy patients). Linear regression was used to obtain mean differences (or ratios if ln-retransformed because of skewedness) adjusted for age, sex, body mass index, comorbidities. For aim 2, pre- and postoperative samples of 85 arthroscopy patients were compared, for which mean changes were obtained.

RESULTS

In patients with lower-leg injury (aim 1), endogenous thrombin potential, thrombin peak, velocity index, FPA and TAT were increased as compared with controls. In arthroscopy patients (aim 2), pre- and postoperative levels were similar for all parameters.

CONCLUSION

Lower-leg trauma increases thrombin generation both ex vivo and in vivo, in contrast to knee arthroscopy. This may imply that the pathogenesis of VTE is different in both situations.

Effect of high-dose statin therapy on coagulation factors: Lowering of factor XI as a modifier of fibrin clot properties in coronary artery disease

BACKGROUND

Multiple pleiotropic effects of statins include antithrombotic properties with formation of looser fibrin networks more susceptible to lysis. Recently, rosuvastatin 20 mg/d has been reported to decrease coagulation factors (F) VII, FVIII and FXI in venous thrombosis patients.

OBJECTIVES

We investigated how high-dose statin therapy recommended in coronary artery disease (CAD) alters plasma levels of coagulation factors and if such changes might affect fibrin clot properties.

METHODS

We studied 130 advanced CAD patients, who initially did not achieve the target low-density lipoprotein cholesterol (LDL-C). Before high-dose statin therapy (rosuvastatin 40 mg/d or atorvastatin 80 mg/d) and 6-12 months after its initiation, FII, FV, FVII, FVIII, FIX, FX, FXI and fibrinogen were assessed. We evaluated the impact of statin-induced alterations to the factors on plasma fibrin clot permeability (Ks) reflecting a fibrin pore size, and clot lysis time (CLT) reflecting fibrinolytic potential.

RESULTS

At baseline LDL-C (median 3.2, interquartile range 2.7-3.7 mmol/L) was independently associated solely with FXI (β = 0.58, P < 0.001). Median LDL-C reduction by 25% (P < 0.001) on high-dose statin treatment was accompanied by lowering of FVII, FVIII, and FXI (for all P < 0.001). On high-dose statin treatment, Ks (R = 0.65, P < 0.001) inversely associated with CRP (β = -0.41, P < 0.001), LDL-C (β = -0.26, P = 0.001), and FXI (β = -0.18, P = 0.016). In turn, CLT (R = 0.45, P < 0.001) was positively associated with LDL-C (β = 0.19, P = 0.043) and FXI (β = 0.17, P = 0.049).

CONCLUSIONS

High-dose statin therapy in CAD patients decreases FVII, FVIII, and FXI. The statin-induced reduction in FXI may contribute to less prothrombotic fibrin clot phenotype, indicating additional antithrombotic effect of high-dose statins.

Decreased protein C activity, lower ADAMTS13 antigen and free protein S levels accompanied by unchanged thrombin generation potential in hospitalized COVID-19 patients

INTRODUCTION

COVID-19 is associated with an increased thromboembolic risk. However, the mechanisms triggering clot formation in those patients remain unknown.

PATIENTS AND METHODS

In 118 adult Caucasian severe but non-critically ill COVID-19 patients (median age 58 years; 73 % men) and 46 controls, we analyzed in vitro plasma thrombin generation profile (calibrated automated thrombogram [CAT assay]) and investigated thrombophilia-related factors, such as protein C and antithrombin activity, free protein S level, presence of antiphospholipid antibodies and factor V Leiden R506Q and prothrombin G20210A mutations. We also measured circulating von Willebrand factor (vWF) antigen and a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13) antigen and activity. In patients, blood samples were collected on admission to the hospital before starting any therapy, including heparin. Finally, we examined the relationship between observed alterations and disease follow-up, such as thromboembolic complications.

RESULTS

COVID-19 patients showed 17 % lower protein C activity, 22 % decreased free protein S levels, and a higher prevalence of positive results for IgM anticardiolipin antibodies. They also had 151 % increased vWF, and 27 % decreased ADAMTS13 antigens compared with controls (p < 0.001, all). On the contrary, thrombin generation potential was similar to controls. In the follow-up, pulmonary embolism (PE) occurred in thirteen (11 %) patients. They were characterized by a 55 % elevated D-dimer (p = 0.04) and 2.7-fold higher troponin I (p = 0.002) during hospitalization and 29 % shorter time to thrombin peak in CAT assay (p = 0.009) compared to patients without PE.

CONCLUSIONS

In COVID-19, we documented prothrombotic abnormalities of peripheral blood. PE was characterized by more dynamic thrombin generation growth in CAT assay performed on admittance to the hospital.

Patients with multiple myeloma and monoclonal gammopathy of undetermined significance have variably increased thrombin generation and different sensitivity to the anticoagulant effect of activated protein C

BACKGROUND

Patients with multiple myeloma (MM) are at high risk of thrombosis especially when receiving immunomodulatory therapy. Thrombotic risk in patients with monoclonal gammopathy of undetermined significance (MGUS) may also be increased. Although activated protein C (APC) resistance has been linked to an increased risk of thrombosis in MM, little is known about how APC influences thrombotic risk in MGUS. We compared thrombin generation (TG) in MM and MGUS patients to that of healthy controls (HCs) and investigated the exogenous effect of APC on TG in these groups.

METHODS

Hemostasis tests including factor VIII (FVIII) and von Willebrand factor (vWF) levels were measured in platelet-poor plasma in 14 untreated MM patients, 34 MGUS patients, and 30 age and sex-matched HCs. TG assay was performed with or without the addition of APC.

RESULTS

Peak thrombin and velocity index were significantly higher in MM and MGUS patients compared to HCs, while MM patients also had elevated endogenous thrombin potential (ETP). In MGUS cases, ETP and peak thrombin values significantly correlated with FVIII and vWF levels. In the presence of APC, peak thrombin and ETP were reduced in MGUS and control plasmas whereas lagtime and time to peak were significantly prolonged. In contrast, adding APC to MM plasma had no effect on any TG parameters.

CONCLUSIONS

Hypercoagulability was observed in MM and even in MGUS cases with very low monoclonal protein concentration. In MM patients, APC had no effect on TG, but it attenuated TG in MGUS patients.

Prognostic value of an automated thrombin generation assay in COVID-19 patients entering hospital: A multicentric, prospective observational study

INTRODUCTION

The prognostic significance of the thrombin generation assay (TGA) with a thrombomodulin (TM) challenge in patients entering hospital with severe COVID-19 is uncertain.

METHODS

We prospectively evaluated an automated TGA (aTGA) using the ST-ThromboScreen® assay and ST-Genesia® analyser in 179 patients with severe COVID-19 during their admission to 2 university hospitals. The primary outcome was early survival at Day 28 (D28). Secondary outcomes were late survival at Day 90 (D90), later transfer to an intensive care unit (ICU), and occurrence of any thrombotic complications during hospitalisation.

RESULTS

Among the 174 patients, 50 were initially admitted to ICUs. Forty-two were transferred to ICUs before D28. Fourteen patients, all in ICUs, died before D28, and 20 before D90, all but 1 in ICUs. None of the aTGA-derived results were associated with vital status either at D28 or D90. Nine patients had a thrombotic event with no association with the aTGA results. Later transfer to the ICU was associated with higher velocity index, thrombin peak height and endogenous thrombin potential (ETP) values of the aTGA performed with TM, and mainly with a lower TM-induced decrease in ETP (odds ratio 15.5 (2.15-132), p = 0.009).

CONCLUSIONS

aTGA, a global assay supposed to evidence coagulopathy, could predict neither early or late survival, nor thrombotic events, in hospitalised COVID-19 patients. Its clinical justification in that setting is thus unlikely. A relative resistance of the ETP to TM was associated with later transfer to the ICU and deserves further investigation.

Enhanced thrombin generation detected with ST-Genesia analyzer in patients with newly diagnosed multiple myeloma

The issue of how to identify newly diagnosed multiple myeloma (NDMM) patients requiring thromboprophylaxis remains unsolved. Several changes in thrombin generation (TG)-derived parameters have been described in multiple myeloma (MM) patients recently. Assessment of prothrombotic risk with a fully automated TG analyzer could reduce interlaboratory variability. Our objective was to determine whether ST-Genesia^® could reveal a hypercoagulable state in NDMM compared to healthy controls. We conducted a multicenter observational study of NDMM requiring initial treatment to compare TG parameters obtained with ST-Genesia^® analyzer and ST-ThromboScreen^® reagent with a control group. Clinical data were obtained from medical records and blood samples were collected before initial anti-myeloma therapy. A thrombophilia panel was performed in all patients. Compared to age- and sex-matched controls (n = 83), NDMM patients (n = 83) had significantly higher peak height, higher velocity index, shorter time-to-peak and lower percentage of endogenous thrombin potential (ETP) inhibition after adding thrombomodulin (TM) (ETP%inh). NDMM on prophylactic low molecular weight heparin (LMWH) showed reduced both peak height and velocity index compared to NDMM who had not yet started VTE prophylaxis, similar to that of controls. Moreover, partial correction of ETP%inh was observed in MM patients on LMWH. The presence of a thrombophilia did not modify the TG phenotype. Untreated NDMM patients showed an enhanced TG, regardless of their thrombophilia status. They generate a higher peak of thrombin, take less time to produce it, and exhibit resistance to TM inhibition. Our findings suggest that standard prophylactic dose of LMWH may reduce TG at levels of healthy controls.

Evaluation of Activated Protein C Resistance Using Thrombin Generation Test

Activated protein C (APC) resistance (APCR) has been identified as a risk factor of venous thromboembolism (VTE). A mutation at the level of factor (F) V has at first permitted the description of this phenotypic pattern and corresponded to a transition (guanine to adenine) at nucleotide 1691 in the gene coding for factor V, resulting in the replacement of arginine at position 506 by a glutamine. This confers to this mutated FV a resistance toward the proteolytic action of the complex formed by activated protein C with protein S. However, many other factors also lead to APCR, such as other F5 mutations (e.g., FV Hong Kong and FV Cambridge), protein S deficiency, elevated factor VIII, exogenous hormone use, pregnancy, and postpartum. All these conditions lead to the phenotypic expression of APCR and are associated with an increased risk of VTE. Considering the large population affected, the proper detection of this phenotype is a public health challenge. Currently, two types of tests are available: clotting time-based assays and their multiple variants and a thrombin generation-based assays and the endogenous thrombin potential (ETP)-based APCR assay. As APCR was thought to be uniquely related to the FV Leiden mutation, clotting time-based assays were specifically designed to detect this inherited condition. Nevertheless, other APCR conditions have been reported but were not captured by these clotting methods. Thus, the ETP-based APCR assay has been proposed as a global coagulation test able to these multiple APCR conditions, as it provides much more information, which makes it a potential candidate for screening coagulopathic conditions before therapeutic interventions. This chapter will describe the current method used for the realization of the ETP-based APC resistance assay.

Anticoagulant Activity of Nucleic Acid Nanoparticles (NANPs) Assessed by Thrombin Generation Dynamics on a Fully Automated System

Rapidly reversible anticoagulant agents have great clinical potential. Oligonucleotide-based anticoagulant agents are uniquely positioned to fill this clinical niche, as they are able to be deactivated through the introduction of the reverse complement oligo. Once the therapeutic and the antidote oligos meet in solution, they are able to undergo isothermal reassociation to form short, inactive, duplexes that are rapidly secreted via filtration by the kidneys. The formation of the duplexes interrupts the structure of the anticoagulant oligo, allowing normal coagulation to be restored. To effectively assess these new anticoagulants, a variety of methods may be employed. The measurement of thrombin generation (TG) reflects the overall capacity of plasma to produce active thrombin and provides a strong contribution to identifying new anticoagulant drugs, including DNA/RNA thrombin binding aptamer carrying fibers which are used through this chapter as an example. Here we describe the TG assessed by Calibrated Automated Thrombogram (CAT) assay in a fully automated system. This method is based on the detection of TG in plasma samples by measuring fluorescent signals released from a quenched fluorogenic thrombin substrate and the subsequent conversion of these signals in TG curves.

Dissimilarity in coagulation system in adults after Fontan surgery based on thrombin generations

OBJECTIVES

The Fontan procedure is the treatment of choice in congenital cardiac malformations defined as the single ventricle. Fontan patients are at high risk of thromboembolism, but the exact mechanism of this is poorly understood. The aim of this study was to evaluate an involvement of thrombin generations and microparticles (MPs) in prothrombotic state in adults with Fontan circulation.

METHODS

This study included hospitalized patients after Fontan procedure and healthy volunteers. We assessed laboratory tests including thrombin generation by calibrated automated thrombography in three variants [platelet-poor plasma (impact of coagulation factors), platelet-rich plasma (PRP) (influence of platelets) and related with MPs]. The technique allows for a comprehensive evaluation of the coagulation system.

RESULTS

The study groups consisted of 81 adult Fontan patients [41 females (50.6%); median age 22 interquartile range [20-27] years] and 54 control subjects. In patients with Fontan circulation, higher values of endogenous thrombin potential and peak values were observed for both platelet-poor plasma (+17% and +33%) and MPs (+29% and 41%) compared to controls (all P < 0.05). Moreover, in the Fontan group, we found a 64.9% shorter lag time and a 70.4% time to peak for MP variant (both P < 0.001). Contrarily, analysis in the PRP showed 17.1% of reduced endogenous thrombin potential in Fontan. Furthermore, there were no differences in thrombin synthesis in PRP in Fontan patients receiving aspirin or those with thrombocytopaenia (all P > 0.05).

CONCLUSIONS

This study for the first time showed that thrombin generation associated with MPs may be an important contributor to the prothrombotic state in the Fontan population.

GnRH Antagonist Protocol Enhances Coagulation During Controlled Ovarian Stimulation for IVF

Changes in coagulation and fibrinolysis have been reported in women undergoing controlled ovarian hyperstimulation (COH) supporting a potential hypercoagulable condition related to this treatment. This study aimed at evaluating the changes in fibrin clot properties and thrombin generation induced by two different COH protocols: long with gonadotropin-releasing hormone agonist (GnRH-a) and GnRH antagonist (GnRH-ant). Primary outcomes included determination of plasma fibrin clot properties, including clot permeability (K_s) and efficiency of fibrinolysis using clot lysis time (CLT), along with thrombin generation (prothrombin fragments 1 + 2) and endogenous thrombin potential (ETP) and fibrinolysis inhibitor levels. One hundred twenty-nine infertile women were included in the final analysis. The GnRH-ant protocol resulted in increased ETP (+ 9.8%) and reduced K_s (- 2.4%). Conversely, COH with the GnRH-a protocol reduced thrombin generation by decreasing both ETP (- 6.6%) and F1 + 2 (- 30.8%) together with favorably altered fibrin clot properties represented by increased K_s (+ 21.7%) and reduced CLT (- 13.8%) as well as decreased PAI-1 levels (by 2.5 times). The GnRH-ant compared to the GnRH-a protocol increased PAI-1 levels (+ 77.3%), thrombin generation (9.3% higher ETP), and K_s (+ 13.7%). In the GnRH-a group, post-COH K_s was 14.3% higher (K_s ≥ 7.92 × 10^-9 cm²) in women with positive vs. negative pregnancy outcomes. Our results show that the GnRH-ant protocol enhanced thrombin generation and slightly decreased fibrin clot density. COH with the GnRH-a reduced thrombin generation and improved fibrin clot features. This trial was registered (NCT04166825). Clinical Trial Registration Number: NCT04166825.

Thrombin generation potential is increased in patients with autoimmune inflammatory myopathies

PURPOSE

Dermatomyositis and polymyositis (DM/PM) are rare autoimmune inflammatory myopathies, characterized by an increased risk of cardiovascular and thromboembolic events, likely related to the prothrombotic plasma properties. The aim of this study was to assess the in vitro thrombin generation profile as a biomarker of plasma procoagulant properties in DM/PM patients.

METHODS

In 58 clinically stable DM/PM patients and 67 controls matched for sex, age, body mass index, we measured plasma thrombin generation potential using the Calibrated Automated Thrombinography (CAT) and analyzed its relationship with clinical disease characteristics, including autoantibodies profile.

RESULTS

Patients with DM/PM had a 21% increase in endogenous thrombin potential (ETP), 36% higher peak thrombin concentration, and 11% faster thrombin generation, compared to controls (p ​< ​0.001, all, also after adjustment for potential confounders). Interestingly, although both diseases did not differ in thrombin generation potential, heterogenous variables predicted elevated ETPs in both of them. In DM, that was higher fibrinogen, C-reactive protein, and total cholesterol, whereas in PM, presence of arthritis and increased blood platelet count. Surprisingly, thrombin formation capacity remained in a robust inverse relationship with serum troponin (r ​= ​-0.67, p ​< ​0.001) in the patient group.

CONCLUSIONS

DM/PM patients are characterized by an increased thrombin generation potential, suggesting prothrombotic plasma properties in both diseases. However, more studies are needed to verify its rationale and role in DM/PM clinical course and unfavorable clinical outcomes.

Effect of invasive therapeutic coronary interventions on endothelial cell activation and thrombin generation in patients with chronic total coronary occlusion

BACKGROUND

Percutaneous coronary intervention (PCI) is commonly used treatment for chronic total occlusion (CTO). PCI can be performed in two different ways using wire escalation (WE) or subintimal dissection and reentry (DR) technique. During both procedures patients are treated with anticoagulants, however a substantial activation of coagulation cascade is expected, which may affect clinical outcome.

OBJECTIVES

Our aim was to compare the impact of WE and DR techniques regarding endothelial cell activation and thrombin formation.

METHODS

Fifty patients after CTO-PCI were enrolled into this study. Blood samples were obtained before PCI, at 48 h and 3-6 months after the intervention to measure soluble endothelium-specific markers and to investigate thrombin generation.

RESULTS

Twenty-nine patients were treated with WE, 21 received DR. In the DR group, soluble VCAM-1 (vascular cell adhesion molecule-1) and ICAM-1 (intercellular cell adhesion molecule-1) concentrations were gradually elevated and remained significantly increased at 3-6 months (p = 0.006 and p = 0.037, respectively) compared to pre-PCI. Furthermore, significant decrease in lagtime (p = 0.004) and time to peak (p = 0.002) with a substantial increment in peak thrombin (p = 0.001) were observed in these patients. In contrast, no significant alteration was found in the WE cohort. Clinical complications (myocardial infarction, stroke, thrombosis, revascularization) did not occur in the first 9 months of follow-up period in either group.

CONCLUSION

Although DR intervention induces more thrombin generation with a larger degree of endothelium activation compared to WE, this technique does not cause more clinical complications.

A description of the coagulopathy characteristics in amniotic fluid embolism: a case report

Amniotic fluid embolism is frequently associated with coagulopathy. However, the exact nature and evolution of the bleeding disorder is incompletely understood. We report a case of clinically diagnosed amniotic fluid embolism associated with major haemorrhage and coagulopathy. We measured sequential levels of all individual clotting factors, thrombin generation, fibrinogen, and D-dimer levels over the course of the event, beginning shortly after the patient's initial collapse and during the subsequent resuscitation, to identify the specific abnormalities of coagulation from stored blood samples. A better understanding of amniotic fluid embolism and the associated coagulopathy is an important area of research to inform targeted treatment of the coagulopathy and improve outcomes for patients.

Relationships between coagulation factors and thrombin generation in a general population with arterial and venous disease background

Background

The current study aims to identify the relationships between coagulation factors and plasma thrombin generation in a large population-based study by comparing individuals with a history of arterial or venous thrombosis to cardiovascular healthy individuals.

Methods

This study comprised 502 individuals with a history of arterial disease, 195 with history of venous thrombosis and 1402 cardiovascular healthy individuals (reference group) from the population-based Gutenberg Health Study (GHS). Calibrated Automated Thrombography was assessed and coagulation factors were measured by means of BCS XP Systems. To assess the biochemical determinants of TG variables, a multiple linear regression analysis, adjusted for age, sex and antithrombotic therapy, was conducted.

Results

The lag time, the time to form the first thrombin, was mainly positively associated with the natural coagulant and anti-coagulant factors in the reference group, i.e. higher factors result in a longer lag time. The same determinants were negative for individuals with a history of arterial or venous thrombosis, with a 10 times higher effect size. Endogenous thrombin potential, or area under the curve, was predominantly positively determined by factor II, VIII, X and IX in all groups. However, the effect sizes of the reported associations were 4 times higher for the arterial and venous disease groups in comparison to the reference group.

Conclusion

This large-scale analysis demonstrated a stronger effect of the coagulant and natural anti-coagulant factors on the thrombin potential in individuals with a history of arterial or venous thrombosis as compared to healthy individuals, which implicates sustained alterations in the plasma coagulome in subjects with a history of thrombotic vascular disease, despite intake of antithrombotic therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12959-022-00392-0.

Extended Coagulation Profiling in Isolated Traumatic Brain Injury: A CENTER-TBI Analysis

BACKGROUND

Trauma-induced coagulopathy in traumatic brain injury (TBI) remains associated with high rates of complications, unfavorable outcomes, and mortality. The underlying mechanisms are largely unknown. Embedded in the prospective multinational Collaborative European Neurotrauma Effectiveness Research in Traumatic Brain Injury (CENTER-TBI) study, coagulation profiles beyond standard conventional coagulation assays were assessed in patients with isolated TBI within the very early hours of injury.

METHODS

Results from blood samples (citrate/EDTA) obtained on hospital admission were matched with clinical and routine laboratory data of patients with TBI captured in the CENTER-TBI central database. To minimize confounding factors, patients with strictly isolated TBI (iTBI) (n = 88) were selected and stratified for coagulopathy by routine international normalized ratio (INR): (1) INR < 1.2 and (2) INR ≥ 1.2. An INR > 1.2 has been well adopted over time as a threshold to define trauma-related coagulopathy in general trauma populations. The following parameters were evaluated: quick's value, activated partial thromboplastin time, fibrinogen, thrombin time, antithrombin, coagulation factor activity of factors V, VIII, IX, and XIII, protein C and S, plasminogen, D-dimer, fibrinolysis-regulating parameters (thrombin activatable fibrinolysis inhibitor, plasminogen activator inhibitor 1, antiplasmin), thrombin generation, and fibrin monomers.

RESULTS

Patients with iTBI with INR ≥ 1.2 (n = 16) had a high incidence of progressive intracranial hemorrhage associated with increased mortality and unfavorable outcome compared with patients with INR < 1.2 (n = 72). Activity of coagulation factors V, VIII, IX, and XIII dropped on average by 15-20% between the groups whereas protein C and S levels dropped by 20%. With an elevated INR, thrombin generation decreased, as reflected by lower peak height and endogenous thrombin potential (ETP), whereas the amount of fibrin monomers increased. Plasminogen activity significantly decreased from 89% in patients with INR < 1.2 to 76% in patients with INR ≥ 1.2. Moreover, D-dimer levels significantly increased from a mean of 943 mg/L in patients with INR < 1.2 to 1,301 mg/L in patients with INR ≥ 1.2.

CONCLUSIONS

This more in-depth analysis beyond routine conventional coagulation assays suggests a counterbalanced regulation of coagulation and fibrinolysis in patients with iTBI with hemostatic abnormalities. We observed distinct patterns involving key pathways of the highly complex and dynamic coagulation system that offer windows of opportunity for further research. Whether the changes observed on factor levels may be relevant and explain the worse outcome or the more severe brain injuries by themselves remains speculative.

An in situ inferior vena cava ligation-stenosis model to study thrombin generation rates with flow

BACKGROUND

Blood flow-induced shear stress affects platelet participation in coagulation and thrombin generation. We aimed to develop an in vivo model to characterize thrombin generation rates under flow.

METHODS

An in situ inferior vena cava (IVC) ligation-stenosis model was established using C57BL/6 mice. Wild type C57BL/6 mice were fed normal chow diet for two weeks before experiments. On the day of experiments, mice were anesthetized, followed by an incision through the abdominal skin to expose the IVC, which was then ligated (followed by reperfusion through a stenosis for up to 2 h). IVC blood flow rate was monitored using a Transonic ultrasound flow meter. In sham animals, the IVC was exposed following the same procedure, but no ligation was applied. Thrombin generation following IVC ligation was estimated by measuring mouse plasma prothrombin fragment 1-2 concentration. Mouse plasma factor Va concentration was measured using phospholipids and a modified prothrombinase assay. Blood vessel histomorphology, vascular wall ICAM-1, von Willebrand Factor, tissue factor, and PECAM-1 expression were measured using immunofluorescence microscopy.

RESULTS

IVC blood flow rate increased immediately following ligation and stenosis formation. Sizable clots formed in mouse IVC following ligation and stenosis formation. Both plasma factor Va and prothrombin fragment 1-2 concentration reduced significantly following IVC ligation/stenosis, while no changes were observed with ICAM-1, von Willebrand Factor, tissue factor and PECAM-1 expression.

CONCLUSION

Clot formation was successful. However, the prothrombin-thrombin conversion rate constant in vivo cannot be determined as local thrombin and FVa concentration (at the injury site) cannot be accurately measured. Modification to the animal model is needed to further the investigation.

Thrombin generation capacity is enhanced by low antithrombin activity and depends on the activity of the related coagulation factors

Background

Supplementation with antithrombin (AT) concentrates is now common in the treatment of congenital and acquired AT deficiency. However, there is no established consensus on the target and timing of supplementation. We aimed to elucidate the effects of AT deficiency on the balance between coagulation activation and inhibition using a thrombin generation assay as in vitro global assay.

Methods

Samples were prepared by admixing commercially acquired AT-deficient plasma with < 1% AT activity with pooled normal plasma. The AT activity in each sample was adjusted to 100, 90, 70, 50, 40, 30, 10, 5, and < 1%. A thrombin generation assay was performed in each sample. AT concentrate-spiked samples were also prepared by adjusting the AT activities in four types of the concentrates: one recombinant and three plasma-derived AT concentrates. The final targeted AT activities in the samples were adjusted to 100, 50, 30, and 5% by spiking each concentrate into the AT-deficient plasma. We also prepared samples with five levels of prothrombin time (PT) % in coagulation factors with the AT activity fixed at 30% by dilution by mixing AT-deficient plasma and normal plasma with Owren’s veronal buffer to adjust the coagulation factor activities in several proportions. The theoretical target PT% values were 100, 66, 50, 40, and 30%. A thrombin generation assay was performed on all samples.

Results

The ability to generate thrombin depended on the AT activity, and the amount of thrombin generation was increased as AT was decreased. Additionally, the amount of thrombin generation was changed significantly when AT activity was ≤ 50%, indicating that AT suppressed thrombin generation. In particular, thrombin generation was remarkable when AT activity was < 30%, and it can be assumed that the prognosis is poor due to organ failure from thrombotic tendency.

Conclusions

The results presented in this basic research were found to be consistent with the clinical findings to date. The mechanism by which 30–50% of AT activity is set as the clinical boundary was elucidated by the thrombin generation assay.

Obesity as a Thrombogenic and Cardiovascular Risk Factor in Children

BACKGROUND/AIMS

Obesity leads to increased risk of thromboembolic events in adults, but few studies have addressed the relationship between obesity and thrombogenic risk during childhood. The aim of this study was to evaluate the prothrombotic state of obese children in comparison with healthy children.

METHODS

Thrombin generation, fibrinogen, and D-dimer levels, along with metabolic parameters, were measured in 72 prepubertal children, of which 47 were obese and 25 eutrophic.

RESULTS

A significant increase in thrombin generation, fibrinogen, and dyslipidemia was found among obese patients.

CONCLUSION

A prothrombotic state develops in childhood obesity during the prepubertal phase.

Impact of frozen thawed embryo transfer in hormone substituted cycles on thrombotic risk markers

INTRODUCTION

Fertility treatment with frozen thawed embryo transfer (FET) is widely used. Women treated in artificial cycles (AC-FET) receive high doses of estrogen in contrast to natural cycles (NC-FET), where no estrogen is administered. Estrogen substitution may be associated with increased risk of thromboembolism. Our aim is therefore to characterize changes in blood coagulation parameters defined as surrogate thrombotic risk markers in women undergoing estrogen substitution during AC-FET.

MATERIALS

In our prospective cohort study, we enrolled 34 women in either: AC-FET (n = 19) or NC-FET (n = 15). Women were recruited at the Department of Obstetrics and Gynaecology, Horsens Fertility Clinic, Denmark, from August 2019 - November 2020. Blood samples were obtained at four timepoints. Thrombin generation, platelet aggregation and fibrinolysis were evaluated as thrombotic risk markers.

RESULTS

Within the AC-FET group, we found a significantly shorter lagtime (p < 0.05) and time to peak (TTP) (p < 0.001) after hormone substitution compared to baseline. Furthermore, a significantly higher mean peak (p < 0.0001) and larger endogenous thrombin potential (ETP) (p < 0.0001) was observed. When compared to the NC-FET group, women receiving AC-FET had a significantly shorter mean TTP (p < 0.005), higher mean peak (p < 0.0001) and larger ETP (p < 0.05). Additionally, we demonstrated a significantly prolonged lysis time within the AC-FET group (p < 0.001).

CONCLUSION

Our results indicate that women receiving AC-FET have a significantly increased thrombin generation which may increase the thromboembolic risk in women being estrogen substituted.

Hemostasis testing in patients with liver dysfunction: Advantages and caveats

Due to concomitant changes in pro- and anti-coagulant mechanisms, patients with liver dysfunction have a “rebalanced hemostasis”, which can easily be tipped toward either a hypo- or a hypercoagulable phenotype. Clinicians are often faced with the question whether patients with chronic liver disease undergoing invasive procedures or surgery and those having active bleeding require correction of the hemostasis abnormalities. Conventional coagulation screening tests, such as the prothrombin time/international normalized ratio and the activated partial thromboplastin time have been demonstrated to have numerous limitations in these patients and do not predict the risk of bleeding prior to high-risk procedures. The introduction of global coagulation assays, such as viscoelastic testing (VET), has been an important step forward in the assessment of the overall hemostasis profile. A growing body of evidence now suggests that the use of VET might be of significant clinical utility to prevent unnecessary infusion of blood products and to improve outcomes in numerous settings. The present review discusses the advantages and caveats of both conventional and global coagulation assays to assess the risk of bleeding in patients with chronic liver disease as well as the current role of transfusion and hemostatic agents to prevent or manage bleeding.

Resistance to thrombomodulin correlates with liver stiffness in chronic liver disease a prospective single-center cohort study

INTRODUCTION

Chronic liver disease (CLD) is characterized by changes in haemostasis, embracing both hypo- and hypercoagulability. Global hemostatic tests such as thrombin generation assays evaluate the hemostatic balance, to better assess bleeding and thrombotic risks. In addition, procoagulant state in patients with CLD has been demonstrated using modified thrombin generation assays with thrombomodulin, a cofactor for protein C activation. In this study, we prospectively determined thrombin generation and thrombomodulin resistance in patients with CLD staged with liver stiffness measurement (LSM), using both the fully automated analyzer ST Genesia® Thrombin Generation System (STG) and the calibrated automated thrombogram assay (CAT).

MATERIALS AND METHODS

Demographic, clinical and laboratory characteristics, and blood samples were collected from 65 patients with CLD. Liver stiffness was measured by transient elastography, and thrombin generation and thrombomodulin resistance, by STG and CAT.

RESULTS

Patients were separated based on LSM of <21 and ≥21 kilopascals (kPa). The propagation rate of thrombin generation was higher in patients with LSM ≥21 kPa and the thrombin generation rate increased as LSM increased. In addition, thrombomodulin resistance assessed by STG and CAT was higher in patients with LSM ≥21 kPa. However, ETP inhibition by activated protein C was comparable in patients with LSM <21 and ≥21 kPa. Finally, LSM correlated with most thrombin generation parameters.

CONCLUSION

The STG automated system may have value in the assessment of patients with chronic liver disease in the routine coagulation laboratory. LSM ≥21 kPa identify a procoagulant phenotype in these patients, including thrombomodulin resistance.

Calibrated automated thrombogram II: removing barriers for thrombin generation measurements

BACKGROUND

Thrombin generation (TG) assessed by Calibrated Automated Thrombogram (CAT-I) reflects the overall capacity of plasma to generate thrombin, thus evaluating the balance between the anti- and procoagulant processes. However, with this method the calibrator curve is usually not measured until completion which has a severe impact on the calculation of the TG parameters, especially under conditions where almost all substrate is consumed. In addition, direct thrombin inhibitor (DTI) cannot be present in the calibration sample due to inhibition of the calibrator. We have developed a modified TG assay (CAT-II) and performed head-to-head comparison with the CAT-I method using the same fluorometer. Furthermore, we have compared our CAT-II method to a new automated TG instrument (ST®-Genesia) using the same calibration method.

METHODS

TG was assessed with CAT-I and CAT-II using the same fulorometer and with ST®-Genesia in control plasma and plasma containing different anticoagulants (dabigatran, rivaroxaban, apixaban) and plasmas to which common interfering substances, bilirubin, hemoglobin and lipids were added. In CAT-I, calibration was against the same plasma containing calibrator in the presence of fluorogenic substrate (Z-GGR-AMC). In contrast, CAT-II method and ST®-Genesia used a standard concentration of thrombin in buffer and 7-amino-4-methylcoumarin (AMC) in a separate plasma sample for calibration.

RESULTS

TG obtained from CAT-I using anticoagulant-free plasmas was lower compared with TG from CAT-II but both methods demonstrated an intra-assay variation less than 5% on all measured parameters. When comparing the two different calibration methods in the presence of different anticoagulants, a high correlation was seen in the presence of rivaroxaban and apixaban (R² > 0.97), but not with dabigatran, a direct thrombin inhibitor. CAT-II method showed dose-dependent inhibition of TG in the presence of dabigatran, while CAT-I was not able to detect it. Both methods were able to correct for the interfering substances.

CONCLUSIONS

Our results showed high similarity between the results of CAT-I and CAT-II method when it is applied in control plasmas and plasmas not inhibited with a direct thrombin inhibitor. Furthermore, both the CAT-II method and ST-Genesia using the same calibration method were able to detect the effect of all oral anticoagulants. Taken together, applying a new calibration method is a significant improvement for monitoring patients on direct thrombin inhibitors while not introducing any bias to results obtained on other types of samples.

Absence of hypercoagulability after nCoV-19 vaccination: An observational pilot study

BACKGROUND

It is still unknown whether COVID-19 vaccines induce a prothrombotic state or increase the hypercoagulable condition in subjects with a predisposition to thrombosis.

OBJECTIVES

We evaluated the coagulation profile in a series of healthy subjects who received the first dose of the BNT162b2 or the ChAdOx1 vaccines and assessed whether hypercoagulability developed.

PATIENTS/METHODS

Volunteers among the staff of the University of Padua or health care professionals in the Padua University Hospital who had received either the ChAdOx1 or BNT162b2 vaccine in the previous 10 ± 2 days were eligible. A cohort of unvaccinated volunteers among family members of the University staff acted as control group. Global coagulation monitoring was assessed by whole blood rotational thromboelastometry, whole blood impedance aggregometry and thrombin generation. Platelet count was also obtained.

RESULTS

One hundred and ninety subjects were enrolled: 101 (53.2%) received the ChAdOx1 vaccine and 89 (46.8%) the BNT162b2 vaccine. Twenty-eight non-vaccinated subjects acted as controls. Thromboelastometry parameters were all comparable among groups. Thrombin receptor activating peptide (TRAP)-, ADP- and ASPI-induced platelet aggregation were similar among groups, as well as platelet count. Endogenous thrombin potential (ETP) was comparable among groups. The results were confirmed after controlling for age, gender and hormonal. Considering women taking combined oral contraceptives or thrombophilia carriers, no differences were detected in thromboelastometry or thrombin generation parameters between subjects who received ChAdOx1 vs. BNT162b2 vaccines.

CONCLUSIONS

No significant activation of fibrinogen-driven coagulation, plasma thrombin generation or clinically meaningful platelet aggregation after ChAdOx1 or BNT162b2 vaccination was observed.

Patients with acute and chronic coronary syndromes have elevated long-term thrombin generation

Coronary artery disease is a leading cause of morbidity and mortality worldwide. Despite significant advances in revascularization strategies and antiplatelet therapy with aspirin and/or P2Y₁₂ receptor antagonist, patients with acute coronary syndrome (ACS) continue to be at long-term risk of further cardiovascular events. Besides platelet activation, the role of thrombin generation (TG) in atherothrombotic complications is widely recognized. In this study, we hypothesized that there is an elevation of coagulation activation persists beyond 12 months in patients with ACS and chronic coronary syndrome (CCS) when compared with healthy controls. We measured TG profiles of patients within 72 h after percutaneous coronary intervention, at 6-month, 12-month and 24-month. Our results demonstrated that TG of patients with ACS (n = 114) and CCS (n = 40) were persistently elevated when compared to healthy individuals (n = 50) in peak thrombin (ACS 273.1 nM vs CCS 287.3 nM vs healthy 234.3 nM) and velocity index (ACS 110.2 nM/min vs CCS 111.0 nM/min vs healthy 72.9 nM/min) at 24-month of follow-up. Our results suggest a rationale for addition of anticoagulation to antiplatelet therapy in preventing long-term ischemic events after ACS. Further research could clarify whether the use of TG parameters to enable risk stratification of patients at heightened long-term procoagulant risk who may benefit most from dual pathway inhibition.

Deciphered coagulation profile to diagnose the antiphospholipid syndrome using artificial intelligence

The antiphospholipid syndrome (APS) is diagnosed by the presence of lupus anticoagulant and/or antibodies against cardiolipin or β₂-glycoprotein-1 and the occurrence of thrombosis or pregnancy morbidity. The assessment of overall coagulation is known to differ in APS patients compared to normal subjects. The accelerated production of key factor thrombin causes a prothrombotic state in APS patients, and the reduced efficacy of the activated protein C pathway promotes this effect. Even though significant differences exist in the coagulation profile between normal controls and APS patients, it is not possible to rely on a single test result to diagnose APS. A neural network is a computing system inspired by the human brain that can be trained to distinguish between healthy subjects and patients based on subject specific data. In a first cohort of patients, we developed a neural networking that diagnoses APS. We clinically validated this neural network in a separate cohort consisting of APS patients, normal controls, controls visiting the hospital for other indications and two diseased control groups (thrombosis patients and auto-immune disease patients). The positive predictive value ranged from 62% in the hospital controls to 91% in normal controls and the negative predictive value of the neural network ranged from 86% in the thrombosis control group to 95% in the hospital controls. The sensitivity of the neural network was higher than 90% in all control groups. In conclusion, we developed a neural network that accurately diagnoses APS in the validation cohort. After further clinical validation in newly diagnosed patients, this neural network could possibly be clinically implemented to diagnose APS based on thrombin generation data.

Thrombin generation is associated with ischemic stroke at a young age

INTRODUCTION

Understanding the underlying mechanisms in ischemic stroke (IS) in young adults remains challenging. Thrombin activates processes that contribute to the development and progression of arterial diseases. We investigated the association between thrombin generation (TG) and a first IS or transient ischemic attack (TIA) in young adults.

METHODS

In this case-control study, we included consecutive patients (≤45 years in men, ≤55 years in women) with a first IS or TIA (n = 160) and healthy controls (n = 160). TG was determined with the calibrated automated thrombogram (CAT) assay. Logistic regression was used to analyze the association between TG and IS. Men and women were analyzed separately.

RESULTS

TG started earlier, reached its peak earlier and was also terminated earlier in patients than in healthy controls. Peak height (PH) was higher in patients than in controls, 227 nM (25th-75th percentile 145-326) versus 179 nM (110-294), p = 0.02. The endogenous thrombin potential (ETP) was not different in patients and controls, 1530 nM·min (1089-2045) versus 1454 nM·min (1011-2139), p = 0.52. Lag time (LT) (Odds Ratio (OR) 0.91 (95% confidence interval (CI) 0.83-0.99)), time to peak (TTP) (OR 0.91, 95% CI 0.84-0.97) and time to tail (TTT) (OR 0.92, 95% CI 0.88-0.97) were associated with a first IS and TIA. In men LT, TTP and TTT were associated with IS, but not in women.

CONCLUSIONS

We found that TG parameters are associated with a first IS in young patients. Further prospective studies are warranted to elucidate the role of TG in IS.

Prothrombotic abnormalities in patients with multiple myeloma and monoclonal gammopathy of undetermined significance

BACKGROUND

Multiple myeloma (MM) and its precursor condition, monoclonal gammopathy of undetermined significance (MGUS) have an increased risk of thrombotic events, especially during anti-myeloma treatment. Many different underlying causes for this hypercoagulability have been suggested, but current techniques to identify abnormalities in these patients are sparse and inefficient. The aim of this study was to assess the hypercoagulability in MGUS and MM patients through various coagulation analyses and identify changes in the MM patients throughout their treatment regimen.

MATERIALS AND METHODS

Platelet-free plasma from 38 MM patients, 19 MGUS patients and 34 healthy controls were tested for hypercoagulability using calibrated automated thrombogram, a procoagulant phospholipid assay, a microvesicle-associated (MV) tissue factor (TF) assay, and a cell-free deoxyribonucleic acid (cf-DNA) assay as a surrogate measurement for neutrophil extracellular traps (NETs).

RESULTS

MGUS and MM patients both had elevated thrombin generation and procoagulant phospholipid activity in comparison to the control subjects. MM, and partly MGUS, showed increased MV-TF activity, however, only MM had increased levels of the cf-DNA.

CONCLUSIONS

Here we demonstrated that hypercoagulability was present in patients with MGUS and MM through increased thrombin generation, possibly due to higher TF and procoagulant phospholipids (PPL) activity. This may be associated to MVs and, for MM patients, be attributed to procoagulant NETs activity; however, this remains to be determined.

Suggestions for global coagulation assays for the assessment of COVID-19 associated hypercoagulability

Introduction

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) infection is associated with a clear prothrombotic phenotype. Although the exact pathophysiological mechanisms are not yet fully understood, thrombosis is clearly a highly important in the prognosis and outcome of COVID-19. As such, there is a need for diagnostic analysis and quantification of the coagulation potential in these patients, both at diagnosis and follow-up. Global coagulation assays like thrombin generation (TG) and rotational thromboelastometry (ROTEM) might be suitable in estimating COVID-19 associated coagulopathy and thrombosis risk. Therefore, we aimed at validating both assays for samples with high levels of fibrinogen and in the presence of anticoagulant heparins, such as commonly observed for COVID-19 ICU patients.

Materials and methods

Calibrated Automated Thrombography (CAT) was optimized to assess plasma thrombin generation in the presence of heparins. The final conditions with either 10 μg/mL Ellagic acid (EA) or PPP Reagent HIGH (high tissue factor; HPPH) were validated according to the EP5 protocol for within-run and between-run variability. Overall variability was well below 10%. To estimate the influences of heparins and high fibrinogen levels, CAT was performed on spiked plasma aliquots from 13 healthy volunteers. Comparable to the CAT method, tPA-ROTEM was used to validate the effect of high fibrinogen and heparins on clotting time, clot firmness and clot lysis parameters.

Results

Our adjusted COVID-19 assay showed a heparin dose dependent decrease in peak height and endogenous thrombin potential (ETP) for both EA and HPPH triggered variants. High fibrinogen did not alter the inhibitory effect of either LMWH or UFH, nor did it influence the peak height or ETP in any of the conditions. The tPA-ROTEM showed a significant prolongation in clotting time with the additions of heparin, which normalized with the addition of high fibrinogen. MCF was markedly increased in all hyperfibrinogenemic conditions. A trend towards increased lysis time and, thus, decreased fibrinolysis was observed.

Conclusion

Thrombin generation and tPA-ROTEM protocols for measurements in the COVID-19 populations were adjusted and validated. The adjusted thrombin generation assay shows good sensitivity for measurements in heparin spiked plasma. High levels of fibrinogen did not alter the assay or the effectiveness of heparins as measured in this assay. t-PA ROTEM was effective in measurement of both high fibrinogen and heparins spiked samples and was sensitive to the expected relevant coagulant changes by these conditions. No clear fibrinolytic effect was observed in different conditions.

Familial hypercholesterolemia: Is there a role for PCSK9 and thrombin generation?

INTRODUCTION

Familial hypercholesterolemia (FH) is an autosomal dominant genetic disease. The prevalence of FH has previously been reported as 1 in 500 in the general population. This study aimed to evaluate the proprotein convertase subtilisin/kexin 9 (PCSK9) levels, lipid profile and thrombin generation in FH patients undergoing treatment or not.

METHODS

Eighty individuals with FH were selected and distributed in 2 groups: individuals treated with statins alone or conjugate therapy (statin + ezetimibe) (T = 53) and those non treated (NT = 27). PCSK9 levels were determined by ELISA, the lipid profile by colorimetric enzyme method and thrombin generation assay (TGA) by CAT method.

RESULTS

Individuals treated with conjugate therapy (statin + ezetimibe) showed a significant reduction in the levels of total cholesterol (TC) low density lipoprotein cholesterol (LDLc) and in the potential for thrombin generation (ETP with low and high concentration of tissue factor), compared to the treated individuals with monotherapy (statins). PCSK9 was positively correlated with increased levels of TC, LDLc and triglycerides, while TGA parameters were positively correlated with PCSK9 and lipid profile.

CONCLUSION

PCSK9 levels appear to be associated with components of the lipid and hemostatic profiles, in addition to being influenced by age. In general, our findings suggest that combined therapy for the treatment of FH is associated with a significant improvement in both lipid and hemostatic profiles assessed by TGA, suggesting a reduction in atherogenic and thrombogenic risks and, therefore, more promising compared to the use of statin monotherapy.

Thrombin Generation in Patients with Atrial Fibrillation Undergoing Percutaneous Coronary Intervention

BACKGROUND

The optimal antithrombotic treatment for patients with atrial fibrillation (AF) that undergo percutaneous coronary intervention (PCI) is controversial. Dual therapy (clopidogrel and a direct oral anticoagulant [DOAC]) is safer than triple therapy (warfarin, aspirin, and clopidogrel), while efficacy is unclear. We aimed to evaluate thrombin generation (TG) under dual and triple therapy.

METHODS

A noninterventional prospective trial in patients with AF undergoing PCI. Patients received 4 weeks of triple therapy with aspirin, clopidogrel, and a DOAC followed by aspirin withdrawal. TG was measured in platelet-rich plasma (PRP) and platelet-poor plasma (PPP) at 3 five to 21 points, day 1 after PCI (TIME 0), 4 weeks after PCI (TIME 1), and 2 weeks after aspirin withdrawal (TIME 2).

RESULTS

Twenty-three patients (18 men, median age 78 years, 83% with acute coronary syndrome) were included. Endogenous thrombin potential (ETP) in PPP was high at TIME 0 compared with TIME 1 (ETP 3,178 ± 248 nM vs. 2,378 ± 222 nM, p = 0.005). These results remained consistent when measured in PRP. No significant difference in ETP was found before (TIME 1) and after aspirin withdrawal (TIME 2) although few patients had high ETP levels after stopping aspirin.

CONCLUSIONS

TG potential is high immediately after PCI and decreases 4 weeks after PCI in patients receiving triple therapy. TG remains constant after aspirin withdrawal in most patients, suggesting that after 1 month the antithrombotic effect of dual therapy may be similar to triple therapy.

Procoagulant State of Sleep Apnea Depends on Systemic Inflammation and Endothelial Damage

INTRODUCTION

Growing evidence shows a hypercoagulable state in obstructive sleep apnea (OSA) that could be a risk factor for thromboembolic disease.

OBJECTIVES

We aimed to elucidate mechanisms involved in the procoagulant profile observed in patients with OSA and to investigate the potential utility of global tests in its characterization.

METHODS

Thirty-eight patients with severe OSA without previous history of thrombosis and nineteen healthy age- and sex-matched controls were included. Kinetic of clot formation was determined using rotational thromboelastometry. Haemostatic capacity of plasma and microparticles was determined by Calibrated Automated Thrombinography. Platelet surface receptors, activation markers and formation of platelet/leukocytes aggregates were analyzed by flow cytometry.

RESULTS

Thromboelastometry showed a procoagulant state in patients with OSA that did not seem to be related to a basal activation of platelets but by the increased existence of platelet/leukocyte aggregates. Patients with OSA presented many signs of endothelial damage such as increased plasma levels of E-selectin and cfDNA and enhanced thrombin generation due to the presence of microparticles rich in tissue-factor, which is related to OSA severity.

CONCLUSIONS

OSA induces an enhancement in the dynamics of clot formation which appears to be caused by at least two pathological mechanisms. First, a greater formation of platelet-leukocyte aggregates; secondly, endothelial damage which provokes a greater procoagulant potential due to the increase in tissue factor-rich microparticles. Moreover, this study has identified thromboelastometry and thrombin generation assay as useful tools to evaluate the prothrombotic state in these patients.

The potential role of emicizumab prophylaxis in severe von Willebrand disease

BACKGROUND

Severe von Willebrand disease (VWD) may be associated with chronic joint damage and may require prophylactic therapy. Emicizumab is a humanized bispecific antibody, which mimics the function of coagulation factor VIII (FVIII), and it has been approved for prophylaxis in hemophilia A.

METHODS

This is the first study assessing the potential future role of emicizumab as an alternative prophylactic treatment in patients with severe VWD, based upon a thrombin generation (TG) ex vivo analysis. We report 51 weeks of successful off label emicizumab prophylaxis in a child with severe VWD and recurrent hemarthroses and progressive arthropathy despite adherence to previous prophylaxis with replacement therapy.

RESULTS AND CONCLUSIONS

Our work demonstrated that ex vivo spiking with emicizumab increased TG in plasma from patients with type 3 VWD. Similar TG results were observed in our treated patient, whose therapy was well tolerated without any adverse events. Both in vitro and ex vivo TG data support sufficient hemostasis without exceeding the range seen in healthy volunteers. Further collaborative studies on the efficacy and safety of emicizumab prophylaxis in severe VWD is warranted.

Prothrombotic hemostasis disturbances in patients with severe COVID-19: Individual daily data

This data article accompanies the manuscript entitled: “Prothrombotic Disturbances of hemostasis of Patients with Severe COVID-19: a Prospective Longitudinal Observational Cohort Study” submitted to Thrombosis Research by the same authors. We report temporal changes of plasma levels of an extended set of laboratory parameters during the ICU stay of the 21 COVID-19 patients included in the monocentre cohort: CRP, platelet count, prothrombin time; Clauss fibrinogen and clotting factors II, V and VIII levels, D-dimers, antithrombin activity, protein C, free protein S, total and free tissue factor pathway inhibitor, PAI-1 levels, von Willebrand factor antigen and activity, ADAMTS-13 (plasma levels); and of two integrative tests of coagulation (thrombin generation with ST Genesia) and fibrinolysis (global fibrinolytic capacity - GFC). Regarding hemostasis, we used double-centrifuged frozen citrated plasma prospectively collected after daily performance of usual coagulation tests. Demographic and clinical characteristics of patients and thrombotic and hemorrhagic complications were also collected from patient's electronic medical reports.