Figure 4

Heatmap based on Pearson correlation coefficients between EBC metabolites and values obtained from clinical test in negativized COVID-19 patients. Rows and columns are rearranged according to the centroid-based correlation matrix-based hierarchical clustering (CMBHC). Blue tone indicates positive correlations between metabolites and clinical data, whereas light tones indicate negative correlations. Correlation values ρ = |0.7| are marked with a double asterisk, while values ρ = |0.5| are labeled with a single asterisk. EBC metabolites are: 1, acetoin; 2, propionate/isobutyrate; 3, propionate/valine; 4, pyruvate; 5, isobutyrate; 6, methanol; 7, 3-hydroxyisovalerate; 8, isovalerate; 9, fatty acids (FA); 10, lactate; 11, formate; 12, trimethylamine; 13, 2-hydroxyisovalerate; 14, isocaproate; 15, isovalerate; 16, valerate; 17, acetate; 18, acetone; 19, serine; 20, isopropanol; 21, glycine; 22, 3-hydroxybutyrate; 23, ethanol. The arrows on top label significant EBC metabolites, whose trend, with respect to healthy subjects, is symbolized by the arrow direction. Statistically significant clinical data are underlined.