PTX3 and ventilator-associated pneumonia: The most widely investigated biomarkers in VAP are procalcitonin and type 1 soluble triggering receptor expressed on myeloid cells (sTREM-1), which have been analysed in both BAL fluid and serum.14–16 In addition, other biomarkers, including elastin fibres, copeptin, nitrated proteins, serum β-d-glucan, pancreatic stone protein, midregional pro-atrial natriuretic peptide, pentraxin 3, Clara cell protein, leucocyte RNA profiles, leptin, and gene expression, have been investigated.17–27 These biomarkers have generally shown inconsistent results, often with poor diagnostic or prognostic utility.