The venous thromboembolic risk and the clot wave analysis: a useful relationship?

BACKGROUND: Hospitalized patients with acute medical conditions have higher venous thromboembolism (VTE) risk. A patient with a final Padua Prediction Score (PPS) of ≥4 is considered to be at high risk for VTE. The aim of this study was to investigate on a possible relationship between PPS, the dynamics of the clot formation, i.e. the clot waveform analysis (CWA) of aPTT, fibrinogen and D-Dimer in a large group of medical patients. METHODS: CWA in terms of velocity (first derivative), acceleration (second derivative), density (Delta) of aPTT, fibrinogen, D-Dimer and PPS for VTE were determined in 801 medical patients divided in three groups (without antithrombotic prophylaxis and high PPS, without antithrombotic prophylaxis and low PPS, with antithrombotic prophylaxis and high PPS) and a group of healthy subjects. RESULTS: CWA, fibrinogen and D-Dimer values were higher in the medical patients with high PPS with or without antithrombotic prophylaxis when compared with patients without antithrombotic prophylaxis with low PPS and healthy subjects. The second derivative, fibrinogen and D-Dimer were significantly associated with a high PPS score (≥4): odds ratio (OR) = 1.53, 95% confidence interval (CI) = 1.03-2.28; OR = 1.91, 95% CI = 1.3-2.79; OR = 3.16, 95% CI = 2.29-4.36, respectively. Interactions between first derivative and D-Dimer (OR = 2.14, 95% CI = 1.23-3.72) and first derivative and fibrinogen (OR = 1.75, 95% CI = 1.02-2.98) were found. CONCLUSIONS: CWA could give useful information to recognize a hypercoagulable state in patients admitted to a medical ward with high and low PPS. First and second derivative aPTT, D-Dimer and fibrinogen levels could be added to PPS to better assess the global thromboembolic risk of these patients.

Is anticoagulative therapy in systemic sclerosis to be reconsidered?

Systemic sclerosis is a rare disease with a high mortality rate. It is a multisystem connective tissue disease due to endothelial autoimmune activation along with tissue and vascular fibrosis, inducing vasculopathy, with an angiogenesis wasting. The endothelial damage provokes platelet activation and immune cell adhesion. The detachment of endothelial cells leads to the interaction of platelets and collagen present in the exposed subendothelial layer. This provokes the activation of several coagulative factors, inducing a pro-thrombotic condition by thrombin generation, which converts fibrinogen into fibrin. Moreover, thrombin has other functions, such as the induction of hyperplasia in smooth muscle cells and fibroblasts, thereby favouring fibrosis. An increased risk of venous thromboembolism has been found in systemic sclerosis, whereas pulmonary hypertension may be due to the obstruction of small pulmonary arteries. Pulmonary veno-occlusive disease may also occur. Warfarin showed inconsistent results, while the outcomes of a randomised, placebo-controlled clinical trial on apixaban versus placebo are still awaited. A new anticoagulation strategy based on anti-factor XI drugs is being developed, with the aim of achieving optimal anticoagulation along with a low risk of bleeding. The molecule types under investigation in this category include monoclonal antibodies, small molecules, natural inhibitors, antisense oligonucleotides, and aptamers. Patients with systemic sclerosis may be ideal candidates for clinical trials planned to analyse the efficacy and safety of these molecules.

Clot Waveform Analysis: From Hypercoagulability to Hypocoagulability - A Review.

CONTEXT.­: Prothrombin time (PT) and activated partial thromboplastin time (aPTT) are coagulative screening tests used for the diagnosis of several pathologic conditions, such as liver failure, coagulation factor deficiencies, anti-phospholipid antibodies (lupus anticoagulant), and factor VIII inhibitors. A new test was developed several years ago to detect the amount of thrombin generated during plasma clotting, using low tissue factor concentrations and fluorogenic substrates, and it has since been used successfully in conditions ranging from hypocoagulable to hypercoagulable states. However, the test is expensive and difficult to perform in nonspecialized laboratories, and efforts have thus been made to find an economic and easily implementable test suitable for routine use, even in nonspecialist laboratories. OBJECTIVE.­: To evaluate clot waveform analysis (CWA) of PT and aPTT, aiming to show the dynamics of clot formation; that is, the "hidden" features of both tests. CWA can be implemented by using an automated coagulometer with dedicated software. The aim of this review was to evaluate whether CWA is able to detect both hypercoagulative and hypocoagulative states. DATA SOURCES.­: Using MedLine, we searched and retrieved articles relating to CWA. We only considered articles published in English, but with no limits in terms of article type, publication year, or geography. CONCLUSIONS.­: CWA was shown to be a reliable test in patients with both hypercoagulable and hypocoagulable states. It represents a simple and inexpensive global test that can easily provide information on the behavior of the coagulation system. Both the first and second derivatives are computed by using dedicated software implemented with an on-board algorithm in a routine automated coagulometer.

Do we need more guidance on thrombophilia testing? Challenges and special considerations.

INTRODUCTION: Thrombophilia testing (TT) is a laboratory procedure designed to detect the risk factors involved in the pathogenesis of vascular occlusions. The role of TT is also controversial because it has a limited impact on the choice and duration of antithrombotic treatments. AREAS COVERED: We reviewed, by examining MEDLINE up to October 2023. Accepted and not accepted thrombophilia markers are discussed along with the appropriateness or not of prescribing TT in several conditions such as: provoked and unprovoked venous thromboembolism (VTE), women who are planning a pregnancy whose relatives had VTE or have a hereditary thrombophilia, before assumption of estro-progestins, after multiple pregnant loss, arterial thrombosis, retinal vein occlusion, and splanchnic vein thrombosis. EXPERT OPINION: TT is not essential in the management of VTE, but it may be useful for limiting adverse events in case of thrombophilia. We expose our criticism of items afforded by other guidelines by presenting our opinion based on both the scientific evidence and clinical practice. We also deal with common mistakes in prescribing and interpretations of TT hoping to purpose an educational approach on this topic. Finally, we emphasize the creation of the expert in hemostasis and thrombosis who should be present in every hospital.

Performance and Interpretation of Clot Waveform Analysis.

The prothrombin time (PT) and the activated partial thromboplastin time (aPTT) are two basic tests for routine purposes, which are widely used in the clinical screening of coagulopathies. PT and aPTT are useful tests for detecting both symptomatic (hemorrhagic) and asymptomatic defects, but they are unsuitable for studying hypercoagulable states. However, these tests are available for studying the dynamic process of clot formation by means of the detection of the clot waveform analysis (CWA), which has been introduced several years ago. CWA can provide useful information on both hypocoagulable and hypercoagulable states. Nowadays it is possible to detect the whole clot formation both in the PT and aPTT tubes starting from the initial step of fibrin polymerization by means of specific and dedicated algorithm implemented in a coagulometer. In particular, CWA provides information on the velocity (first derivative), acceleration (second derivative), and density (delta) of clot formation. CWA has been applied to several pathologic conditions such as coagulation factor deficiency (including congenital hemophilia from factor VIII, IX, or XI deficiency), acquired hemophilia, disseminated intravascular coagulation (DIC), sepsis, replacement therapy management, chronic spontaneous urticarial, and liver cirrhosis, in patients with high venous thromboembolic risk before LMWH prophylaxis, and in patients with different hemorrhagic patterns along with an electron microscopy evaluation of the clot density. We report here materials and methods used for detecting the additional clotting parameters available in both PT and aPTT.

A journey to vasculopathy in systemic sclerosis: focus on haemostasis and thrombosis.

Systemic sclerosis is a multisystem connective tissue disease, characterized by endothelial autoimmune activation, along with tissue and vascular fibrosis leading to vasculopathy and to a progressive loss of angiogenesis. This condition further deranges the endothelial barrier favouring the opening of the endothelial junctions allowing the vascular leak in the surrounding tissues: this process may induce cell detachment which allows the contact between platelets and collagen present in the exposed subendothelial layer. Platelets first adhere to collagen via glycoprotein VI and then, immediately aggregate because of the release of von Willebrand factor which is a strong activator of platelet aggregation. Activated platelets exert their procoagulant activity, exposing on their membrane phospholipids and phosphatidylserine, enabling the adsorption of clotting factors ready to form thrombin which in turn drives the amplification of the coagulative cascade. An essential role in the activation of blood coagulation is the tissue factor (TF), which triggers blood coagulation. The TF is found abundantly in the subendothelial collagen and is also expressed by fibroblasts providing a haemostatic covering layer ready to activate coagulation when the endothelial injury occurs. The aim of this review is to focus the attention on the underlying mechanisms related to haemostasis and thrombosis pathophysiology which may have a relevant role in SSc as well as on a possible role of anticoagulation in this disease.

Chronic spontaneous urticaria: a low-grade disseminated intravascular coagulation only partially reversed by Omalizumab.

Chronic spontaneous urticaria (CSU) is a disorder characterized by wheals and/or angioedema. The coagulation cascade and inflammation pathways are closely linked together. The aim of our study was first to investigate the dynamics of clot formation in plasma (Clot Waveform Analysis, CWA) in a group of 47 patients with CSU along with other coagulative parameters dedicated to the study of hypercoagulability, such as D-Dimer, F 1 + 2 peptide, Fibrinogen, Platelet count and Mean Platelet Volume (MPV). Secondly, 23 out of 47 patients were treated with Omalizumab at four administration intervals from T0 to T4. A statistically significant increase in Activated Partial Thromboplastin (aPTT) ratio, D-Dimer, F1 + 2, Platelet count and MPV was found when compared with 53 healthy controls (HC). In contrast, the 2nd Derivative of aPTT showed lower values than those of the HC. No differences were found between 1st derivative of aPTT and Fibrinogen. D-Dimer only showed a significant difference between T0 and T3. An activation of both coagulation and fibrinolysis along with a weaker clot acceleration may be in agreement with a low-grade DIC. The accelerated turnover of platelets expressed by both an increase in platelet count and MPV further supports this pathway in CSU. Omalizumab does not affect the relationship between the immune and the hemostatic systems.

Clot characterization by multidisciplinary approach: biochemical and imaging parameters in a hypocoagulative setting. A pilot study.

BACKGROUND: Clot characterization is, to the present days, a multimodal approach: scanning the clot by electron microscopy (SEM) is helpful for the visualization of fibrin structure along with laboratory parameters such as the clot waveform analysis (CWA) and thrombin generation in different settings of clot abnormalities. This study aimed to assess whether the coagulative parameters were consistent with the clot images texture acquired by SEM, and therefore to propose a more generalist and integrative approach to clots classification. DESIGN AND METHODS: In this pilot study, the examined population consists of eight healthy subjects, seven patients affected by Acquired Hemophilia A (AHA) and seven patients treated with Vitamin K Antagonists (VKAs), similar for age and gender. We studied the velocity and acceleration (1st and 2nd derivative of the aPTT) of clot formation (CWA), the thrombin generation, and the clots' scanning by SEM. Images acquired with SEM were then analyzed with the MATLAB software with the "Texture Analysis" methods to perform classification. Among the various texture parameters, we reported Contrast and Energy. RESULTS: Significant differences among healthy subjects, patients with AHA and those treated with VKAs were detected for the coagulative parameters. We found no differences between VKAs and AHA patients. Contrast and energy highlighted a significant difference among the three groups in agreement with the laboratory's parameters. We found no significant differences between VKAs and AHA patients. CONCLUSIONS: The use of SEM, CWA and thrombin generation parameters may be a starting point for studies aimed to demonstrate the general characteristics of clot formation in different clinical conditions with a multiparametric approach.

A Sardinian Family with Factor XI Deficiency.

INTRODUCTION: Factor XI (FXI) deficiency is a bleeding disorder which causes a bleeding tendency after trauma or surgery. An inhibitor may be acquired secondary to replacement therapy. AIM: To study on genetical and functional grounds a family admitted to our Haemostasis and Thrombosis Centre for an incidental finding of a prolonged activated partial thromboplastin time (aPTT) in three members. METHODS: aPTT mixing test, dosage of FXI activity and antigen, FXI inhibitor titration, DNA analysis and clot waveform analysis (CWA) were performed. RESULTS: Patients II.1, II.3 and II.4 showed a severe FXI deficiency (0.7, 0.7 and 1.8%, respectively) and low antigen level. Since the proposita was already treated with plasma, the dosage of the inhibitor was determined to be 6.4 Bethesda units. They were homozygous for the p.Glu117Stop mutation. The other family members were heterozygous. The velocity and the maximum acceleration of the clot formation were lower than those of the other family members and the normal subjects but higher than those of patients with acquired haemophilia A. CONCLUSION: A mixing test of a prolonged aPTT should be performed because it will be present both in patients with or without the inhibitor. A molecular analysis in severe FXI deficiency is warranted as it may have prognostic significance. CWA may be helpful for better understanding the pathophysiology of this kind of defect.