This study assessed endothelial dysfunction and platelet activation biomarkers, including PAI, thrombomodulin, von Willebrand antigen (VWF: Ag), von Willebrand factor ristocetin cofactor (VWF: RCo), and P-selectin, to find a reliable biomarker to predict disease severity in COVID-19 patients. This evidence concerns the gene THBD and COVID-19.