Ability of the lung clearance index to detect inflammation and infection in preschool children with cystic fibrosis

Abstract

Introduction: The lung clearance index (LCI) is a marker of global ventilation inhomogeneity derived from the multiple breath washout. The LCI is the first index to decline in young children with cystic fibrosis (CF) and may be a sensitive marker of early lung disease. Aims: We assessed the ability of the LCI to detect the presence of pulmonary inflammation and infection in the lower respiratory tract of preschool children with CF. Method: We measured LCI in 34 children with CF and 17 healthy children (aged 3 to 6 years) prior to the collection of bronchoalveolar lavage fluid (BAL). Results: The LCI was higher in children with CF (8.21 ± 1.3) compared with healthy children (6.63 ± 0.43; p < 0.001; upper limit of normal = 7.48), with 62% having abnormal LCI values. In children with CF, LCI was higher in those with free neutrophil elastase activity (NE) (9.13 ± 0.97) compared with those without NE (7.69 ± 1.40; p < 0.001). The positive and negative predictive values of LCI to detect NE were 92% and 58%, respectively. There was a significant correlation between LCI and the level of NE (spearman correlation (ρ) = 0.52; p = 0.002), and interleukin-8 (ρ = 0.44; p = 0.014). There were no differences in LCI between those with (8.42 ± 1.46) or without a respiratory infection (7.91 ± 1.24; p = 0.30). However, the LCI was higher in children infected with multiple pathogens compared with those uninfected (p = 0.002). Conclusions: We found that the LCI is sensitive to detect the presence of neutrophilic inflammation and multiple pathogens in the lower respiratory tract in preschool children with CF, suggesting LCI may be a useful surveillance tool for early CF lung disease.