SAA4 and COVID-19: These results point to a clear pattern in which some proteins (rate of change > 0.900; Supplementary Data 2) such as neutrophil defensin 3, serum amyloid A (SAA) SAA2-SAA4 readthrough, Apolipoprotein C-IV, and Fibrinogen gamma chain are associated with nonsevere and severe COVID-19 patients, therefore increasing the PR index value of the BPs.