In the only laboratory-based study, Zuo et al., using cell-free DNA (cfDNA), myeloperoxidase-DNA complexes and citrullinated histone H3 as surrogate markers of in vivo neutrophil extracellular trap (NET) formation, reported elevated levels of all three markers in serum samples obtained from hospitalized COVID-19 patients when compared to HCs (82). This evidence concerns the gene MPO and COVID-19.