Fig. 4

COVID-19 positive patients showed statistically significant differentially expressed proteins in exhaled breath. X-axis show difference in intensities and y-axis negative log p-value calculated using a student’s t-test. Significantly differentially expressed upregulated proteins are highlighted in red and downregulated proteins are highlighted in blue. A Volcano plot of differentially expressed proteins between PCR-verified COVID-19 infection (COV-POS) and healthy controls (HCO). B Volcano plot of differentially expressed proteins between COV-POS and patients with respiratory symptoms but with > 2 negative polymerase chain reaction (PCR) tests for COVID-19 (COV-NEG). C Volcano plot of differentially expressed proteins between patients with respiratory symptoms but with > 2 negative polymerase chain reaction (PCR) tests for COVID-19 (COV-NEG) and healthy controls (HCO)