Secondly, there were significant overlaps in the gene expression level in healthy controls and COVID-19 patients in TNFα, CCL2, CCL3, TGFβ, and IL-10 in the aforementioned study, while our study demonstrated that MPO, ADA, CCL22, TNFα, and IL-6 mRNA expression were significantly different between the two groups, with ADA mRNA expression showing the best performance with no overlapping between the interquartile ranges, with reasonable sensitivity and specificity in differentiating infected from uninfected patients. This evidence concerns the gene MPO and COVID-19.