THROMBUS GENERATION UNDER FLOW CONDITIONS IN PATIENTS WITH CIRRHOSIS AND THROMBOCYTOPENIA: THE CIRTAS-STUDY

Background: Thrombocytopenia is a hallmark of cirrhosis, however its effect on the bleeding risk remains uncertain due to a rebalance of hemostasis. Traditional coagulation tests, such as platelet count, prothrombin and activated thromboplastin time, fail to capture the complex interplay of pro- and anti-hemostatic mechanisms and do not reliably predict the bleeding risk in cirrhosis. Global hemostasis assays, including thromboelastometry and thrombin generation, are valid alternatives, however, despite their relevant contribution to understand the complexity of hemostasis in advanced chronic liver disease, they are not recommended for the bleeding risk stratification in clinical practice. An automatized microfluidic system based on a dedicated chip, the Total Thrombus Analysis System (T-TAS®) with HD-CHIP, is a new laboratory tool to assess the thrombus formation under flow in patients with thrombocytopenia, but has never been tested in cirrhosis. Aims: We assessed the reproducibility and accuracy of the Total Thrombus Analysis System (T-TAS®) with HD-CHIP in cirrhotic patients with thrombocytopenia with different clinical stages of severity. Additionally, we compared hemostatic parameters in patients stratified for the threshold of 50,000/mm³ platelet and finally evaluated the clinical and laboratory factors influencing thrombus formation. Methods: Thrombus formation was assessed by using the HD-CHIP of T-TAS®, which analyzes the progressive occlusion of a microchannel coated with tissue factor and type I collagen under flow measured as occlusion start time (OST), occlusion time (OT), and area under the curve (AUC). All analyses were duplicated to measure the reproducibility of the test through the intraclass correlation coefficients (ICC), and Bland-Altman plot. Additional assessments included thrombin generation, thromboelastometry, and markers of inflammation and primary and secondary hemostasis. Linear regression models were used to explore the independent clinical and laboratory determinants of thrombus formation. The statistical significance was for p<0.05. Results: Eighty-one cirrhotic patients with platelet count <90,000/mm³ were enrolled and grouped in Child-Pugh class A (n=20), B/C (n=41), and B/C with bacterial infection (n=20). Clinical and laboratory characteristics were consistent with increasing disease severity and systemic inflammation across the three groups. T-TAS showed excellent reproducibility (ICC>0.9) for all the T-TAS parameters. A higher disease severity was associated with longer OT (p=0.032) and reduced AUC (p=0.025), indicating impaired thrombus formation. This laboratory phenotype was even worse in patients with platelets below 50,000/mm³ for each clinical group considered for this sub-analysis, however the result did not reach the statistical significance. Platelet count and factor VIII levels were independently associated with OT (p=0.003 and p=0.041) and AUC (p=0.018 and p=0.072, respectively) regardless of the clinical group of severity. Conclusion: T-TAS with HD-CHIP is a reproducible tool to test the efficiency of hemostasis in patients with cirrhosis and thrombocytopenia and accurately captures the impact of disease severity on reduced thrombus formation. These findings support the potential of T-TAS as a new promising global hemostatic test in cirrhosis, which warrants further evaluation in clinical studies.