Therefore, regular monitoring of D-dimer, prothrombin, and fibrinogen in COVID-19 is recommended because a significant increase in D-dimer and prothrombin with a decrease in fibrinogen has been observed at days 10–14 in non-survivors, and an elevated D-dimer level (above 1 mcg/mL) has been reported to be a strong independent risk factor in this vulnerable population [16, 19]. Here, F2 is linked to COVID-19.