In particular, in these two cases, some clinical features did not show strong efficiency (e.g., NTproBNP is even lower in the severe case) but the VRmax correctly indicates the right trend (i.e., higher in the severe case) with the highest relative ratio between the severe and non-severe cases, showing high robustness in assessing COVID-19 severity against patient-specific variability in pathophysiological features. Here, NPPB is linked to COVID-19.