Biomarkers of Hypercoagulability and Endothelial Cell Activation in Patients with Severe COVID-19 Admitted at the Intensive Care Unit. the Roadmap-COVID-19 Prospective Observational Study

Introduction: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease 2019 (COVID-19) characterized by acute pneumonia which may progress to respiratory failure and life-threatening complications, including acute respiratory distress syndrome (ARDS) and multisystem organ failure with fatal outcome. COVID-19 should be regarded as a systemic disease involving multiple systems. COVID-19 is associated with excessive inflammation, platelet activation, endothelial dysfunction, blood coagulation activation and fibrin formation. The development of a screening algorithm for the evaluation of endothelial and blood coagulation activation is an urgent need for the optimisation of the management of the patients with severe COVID-19. To this aim biomarkers of endothelial cell activation and hypercoagulability have central place

Aim: The prospective observational monocentric cohort study ROADMAP-COVID-19 study aimed to evaluate the biomarkers of hypercoagulability and endothelial cell activation which they could be used in the development of a screening algorithm in patients with COVID-19

Methods: The ROADMAP-COVID-19 study enrolled 90 consecutive patients hospitalized at Tenon University Hospital (AP-HP, Paris) between March 18^th and April 30^th, 2020 with confirmed SARS-CoV-2 infection admitted to the ICU with clinically deteriorated severe COVID-19 (ICU- group). Patients were assessed upon the first day to the ICU admission. The control group consisted 30 healthy individuals (C-group). All patients and controls were evaluated for, clotting times (PT and aPTT), fibrinogen, D-Dimers, antithrombin (AT), protein C (PC) and protein S (Ps) activity, clotting factors V (FV), VIII (FVIII) and XII (FXII), high molecular weight kininogen (HK), von Willebrand factor (FvW), thrombin generation assay (TG) using TF 20 pM-PPP-Reagent® (Thrombogram-Thrombinoscope from Stago), fibrin monomers (FM), free TFPI and TF activity, thrombomodulin activity (TM), TF expressing microparticles (the ratio TF/TFPI was also calculated) and Heparanase. The IL-6 levels were also measured. All patients hospitalized in conventional medical department or in ICU routinely received thromboprophylaxis with body weight adapted enoxaparin. The ratio of the mean values of each studied biomarker in the ICU and the C-group was calculated. Biomarkers were classified in four clusters (Decrease, Stable, Slight Increase, Moderate Increase and High Increase).

Results :The ICU-group consisted of 102 patients; 87% of these patients were admitted to the ICU directly from the emergency department. Males were 76 out of 102 patients. Age ranged from 30 to 93 years in the W-group. The changes of the biomarkers in patients with COVID-19 admitted at the ICU as compared to healthy individuals with are shown in Table 1. The ICU patients with COVID-19 were characterized by marked increase of IL-6 followed by increase of heparanase and D-dimers. The PPL-ct showed the most important decrease. Patients showed a significant decrease in FXII levels which was associated with a moderate increase of kininogen levels. The levels of the natural coagulation inhibitors as well as the clotting times (PT and aPTT) did not significantly modify in patients as compared to the controls. The rate of the propagation phase of thrombin generation (MRI) and the Peak of thrombin were significantly decrease and the lag-time was prolonged reflecting the antithrombotic effect of treatment with LMWH. Heparanse, free TFPI, and TM showed moderate or high increase. The decreased Ratio of TF/TFPI indicated that the free TFPI release dominated over the release of soluble TF activity.

Conclusion: Patients with severe COVID-19 requiring ICU admission showed inhaled inflammatory reaction, hyperocoagulability and endothelial cell activation whereas platelet activation appeared to be secondary. Among the studied biomarkers the PPL-ct D-dimers and heparanase followed by TFPI, FvW, FM and TM levels appear to be mandatory for hypercoagulability of cellular origin. Interestingly patients with severe COVID-19 showed consumption of FXII indicating intrinsic clotting pathway activation and high levels of HK which also indicates endothelial cell activation. The clinical relevance of these biomarkers for early detection of hypercoagulability of cellular origin in patients with COVID-19 is being evaluated in prospective study.