Neutrophil-to-lymphocyte ratio as a biomarker of acute pulmonary exacerbations in children with cystic fibrosis: a retrospective cohort study

Abstract

BackgroundNeutrophils are key contributors to chronic airway inflammation in cystic fibrosis (CF) lung disease, although airway and blood-based neutrophil markers are seldom used. The neutrophil-to-lymphocyte ratio (NLR) is an accessible biomarker, the clinical utility of which has not been adequately studied.ObjectiveThis study aimed to investigate the characteristics of the NLR in children with CF and its correlations with acute pulmonary exacerbations and spirometry.DesignA previous study had collected clinical data from children with CF for a 3-year period between 2016 and 2021. Retrospectively, NLR values were categorised according to patients’ clinical status during blood sample collection as ‘stable’, ‘acute pulmonary exacerbation’ or ‘elective admission for chronic clinical concern’.Main outcome measuresDemographic characteristics associated with the NLR; changes in NLR values in relation to clinical status; relationship between NLR and lung function.Results141 children with CF were included. NLR values during clinical stability were higher in females and increased with age. For children admitted for intravenous antibiotics, NLR values significantly increased from clinical stability (median (IQR)=1.13 (0.75–1.51)) to acute pulmonary exacerbations (median (IQR)=1.50 (0.96–2.65), p=0.001), but similar changes were not observed in elective admissions. The NLR was not associated with lung function.ConclusionsThe NLR demonstrated associations with clinical status in children with CF with significant elevations during acute pulmonary exacerbations. While its utility as a single-marker measure is limited, monitoring the NLR over time may help identify periods of increased inflammation.