Crucially, platelet activation with the thromboxane A2 receptor agonist U46619 (1 μM) induced a 28-fold increase in ADP-release in COVID-19–positive patients compared to HeC and strikingly, an 89-fold increase between COVID-19–positive patients and HoC (Fig 2C and S2 Table). This evidence concerns the gene TBXA2R and COVID-19.