F2 and COVID-19: In a cohort study, it was found that COVID-19 patients were more likely to have abnormal PT, aPTT, D-dimer, and fibrinogen levels at hospital admission compared to the control group, and a statistically significant increase in fibrinogen levels was found in COVID-19 patients with ARDS (Acute Respiratory Distress Syndrome) compared to those without ARDS [14].