Pulmonary FABP4 is an inverse biomarker of pneumonia in critically ill children and adults

Lower respiratory tract infection (LRTI) is a leading cause of mortality, yet accurate diagnosis remains challenging. We studied two prospective observational cohorts of critically ill patients with acute respiratory failure (pediatric, N=261; adult N=202) and analyzed RNA sequencing data from tracheal aspirate collected following intubation. Patients with LRTI or non-infectious acute respiratory failure were adjudicated by a multi-physician team. We found that FABP4 expression was significantly downregulated in children with confirmed LRTI compared to those with non-infectious respiratory failure, and when incorporated into a diagnostic classifier, achieved an area under the receiver operating characteristic curve (AUC) of 0.90. When tested in the adult cohort, and AUC of 0.85 was attained. These findings suggest that pulmonary FABP4 could serve as a valuable biomarker for the early diagnosis of LRTI in critically ill patients across the age spectrum, offering a potential tool for improving clinical outcomes and reducing unnecessary antibiotic use.