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

BACKGROUND AND AIMS: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.