ANGPT1 and susceptibility to pneumonia measurement: We previously reported that elevation in endothelial biomarkers ANGPT2/ANGPT1 ratio, VCAM1, and vWF distinguished children with ARDS due to indirect (e.g., extrapulmonary sepsis or trauma, shock, transfusion, pancreatitis) compared to direct (e.g., pneumonia, aspiration, drowning) lung injury (Whitney et al., 2020a).