Fig. 5.

Impact of time elapsed since first diagnosis (Dx) on the colorimetric signal (S) obtained after analyzing masks worn during 30 min. (A) Correlation plot; (B) ROC analysis for data points corresponding to masks during the first 3 days since the official diagnosis (black, *p < 0.001), 4-6 days afterwards (red, *p < 0.001) or more than 7 days afterwards (green, **p < 0.05). AUC is the area under the ROC curve. (C) Biosensor signal evolution with time for all participants firstly diagnosed 1 (red), 2 (black), 3 (blue), 4 (green), or 6 (pink) days ago. (D) Signal variation rate as function of time passed since diagnosis for the first sample in the series.