Sputum neutrophil elastase and its relation to pediatric bronchiectasis severity: A cross-sectional study

Sputum neutrophil elastase (NE) is a marker of neutrophilic airway inflammation in bronchiectasis. Yet, not much is known about its role in pediatric bronchiectasis severity. This study aimed to assess the sputum NE value as a biomarker of clinical and radiological severity in pediatric bronchiectasis.

This was a cross-sectional study assessing sputum NE in a total of 50 bronchiectasis patients under the age of 18 years-30 patients with cystic fibrosis (CF) and 20 patients with non-CF bronchiectasis were included. Bronchiectasis severity was assessed using Shwachman-Kulczycki (SK) score, CF-ABLE score, and CF risk of disease progression score, among CF patients, and bronchiectasis severity index (BSI) and FACED criteria among non-CF bronchiectasis patients, associations between sputum NE and bronchiectasis severity were assessed in both patient groups.

Sputum NE was directly correlated with C-reactive protein (r = 0.914, p < 0.001), (r = 0.786, p < 0.001), frequency of exacerbations (r = 0.852, p < 0.001) (r = 0.858, p < 0.001), exacerbations severity (r = 0.735, p = 0.002), (r = 0.907, p < 0.001), and the number of hospital admissions (r = 0.813, p < 0.001), (r = 0.612, p  =0.004) in the last year among CF, and non-CF bronchiectasis patients, respectively. Additional linear correlations were found between sputum NE, CF risk of disease progression score (p < 0.001), CF-ABLE score (p < 0.001), and lower forced expiratory volume 1% of predicted (p = 0.017; ρ = -0.8) among CF patients. Moreover, sputum NE was positively correlated with the neutrophil count (p = 0.018), and BSI severity score (p = 0.039; ρ = 0.465) among non-CF bronchiectasis patients.

Sputum NE may be considered a good biomarker of bronchiectasis severity in both CF and non-CF bronchiectasis patients, as confirmed by the exacerbations rate, CF risk of disease progression, and BSI scores.