Neutrophil-to-Lymphocyte Ratio in Bronchiectasis and it’s Association with Disease Severity – A Single Centre Retrospective Study

Background The neutrophil-to-lymphocyte ratio (NLR), a marker of systemic inflammation, has shown promise in assessing disease severity in chronic respiratory conditions. However, its utility in bronchiectasis remains underexplored. This study evaluated the association between NLR and clinical markers of bronchiectasis severity, including lung function and the Bronchiectasis Severity Index (BSI). Methods In this retrospective cohort study, electronic health records of 213 adults with radiologically confirmed bronchiectasis (2014–2021) were analyzed. NLR was derived from non-exacerbation complete blood counts. Correlations between NLR and spirometry (FEV1% predicted, FVC%, FEV1/FVC), BSI, and microbiological data were assessed using Pearson’s correlation and multivariate regression. Results Mean NLR was 7.05 ± 13.84. NLR correlated negatively with FEV1% PREDICTED (r = − 0.321, *p* < 0.001) and FVC% (r = − 0.342, *p* < 0.001), but not with BSI (*p* = 0.095). Multivariate analysis confirmed NLR as an independent predictor of FEV1% predicted (F = 21.058, *p* < 0.001) and eosinophil count (*p* = 0.019). Ordinal regression linked higher NLR to severe BSI categories (OR = 0.58, 95% CI 0.02–1.13, *p* = 0.041), though effect sizes were modest (Nagelkerke R² = 0.024). Pseudomonas aeruginosa (33.8%) was the most frequent pathogen. Conclusions Elevated NLR reflects worse lung function and may aid in stratifying bronchiectasis severity, particularly as a surrogate for neutrophilic inflammation. However, its inability to correlate strongly with BSI underscores the need for multimodal assessment. NLR is a practical, low-cost biomarker but should complement—not replace—existing tools like BSI. Prospective studies are needed to validate its prognostic utility.