Neutrophil-to-Lymphocyte Ratio in Bronchiectasis and Its Association With Disease Severity-A Single-Center Retrospective Study.

BACKGROUND

The neutrophil-to-lymphocyte ratio (NLR) is a marker of systemic inflammation and has shown promise in assessing disease severity in chronic respiratory conditions including bronchiectasis. This study explores the association between NLR and clinical markers of bronchiectasis severity, including lung function and the Bronchiectasis Severity Index (BSI).

OBJECTIVE

To assess the association between NLR, lung function, and bronchiectasis severity in adults with noncystic fibrosis bronchiectasis.

METHODS

We performed a retrospective single-center study of adults with HRCT-confirmed bronchiectasis identified from electronic health records. Demographic, spirometric, microbiological, BSI, and blood count data were collected. NLR was calculated from the first available complete blood count obtained during clinical stability. Correlation analyses were performed in an outlier-truncated cohort, whereas multivariate general linear models and ordinal regression assessed independent associations with lung function and BSI severity categories.

RESULTS

The cohort included 213 patients; 99 were male and 114 female, with a mean age of 53.9 ± 20.4 years. Most patients had severe bronchiectasis by BSI category. Chronic Pseudomonas aeruginosa colonization was present in 33.8% and was associated with lower FEV₁% predicted. Median NLR was 2.89. NLR showed significant negative correlations with FEV₁% predicted, FVC% predicted, and FEV₁/FVC ratio, but not with continuous BSI score. After adjustment for chronic Pseudomonas colonization, logNLR remained independently associated with FEV₁% predicted and FVC% predicted, but not with BSI score. In ordinal regression, NLR was not independently associated with BSI severity categories. Absolute eosinophil count was the only independent predictor of advanced BSI category.

CONCLUSION

NLR was associated with impaired lung function, but not independently with BSI. NLR may reflect physiological impairment but does not replace established severity tools such as BSI.