MPO and COVID-19: We quantified the increased NETs in the plasma of the male patients with COVID-19 by measuring the circulating cell-free DNA (204.7 ± 138.1 vs. 55 ± 48.3 ng/mL in healthy controls) and MPO activity (793.3 ± 182.7 vs. 318.1 ± 80.3 U/L in healthy controls).