Although this study demonstrated up-regulation of active MMP-9 in pediatric ARDS subjects and association between increased MMP-8 and MMP-9 early in disease course with duration of mechanical ventilation, it is crucial to recognize that examination of MMP-8/9 levels with other previously recognized ARDS biomarkers such as plasma von Willebrand factor antigen, plasminogen activator inhibitor-1 and B-type natriuretic peptide [27]–[29] may provide greater prognostic value than MMP biomarkers alone. Here, SERPINE1 is linked to acute respiratory distress syndrome.