Lung Clearance Index to Track Acute Respiratory Events in School-Age Children with Cystic Fibrosis.

The lung clearance index (LCI) is responsive to acute respiratory events in preschool children with cystic fibrosis (CF), but its utility to identify and manage these events in school-age children with CF is not well defined. To describe changes in LCI with acute respiratory events in school-age children with CF. In a multisite prospective observational study, the LCI and FEV were measured quarterly and during acute respiratory events. Linear regression was used to compare relative changes in LCI and FEV% predicted at acute respiratory events. Logistic regression was used to compare the odds of a significant worsening in LCI and FEV% predicted at acute respiratory events. Generalized estimating equation models were used to account for repeated events in the same subject. A total of 98 children with CF were followed for 2 years. There were 265 acute respiratory events. Relative to a stable baseline measure, LCI (+8.9%; 95% confidence interval, 6.5 to 11.3) and FEV% predicted (-6.6%; 95% confidence interval, -8.3 to -5.0) worsened with acute respiratory events. A greater proportion of events had a worsening in LCI compared with a decline in FEV% predicted (41.7% vs. 30.0%;  = 0.012); 53.9% of events were associated with worsening in LCI or FEV. Neither LCI nor FEV recovered to baseline values at the next follow-up visit. In school-age children with CF, the LCI is a sensitive measure to assess lung function worsening with acute respiratory events and incomplete recovery at follow-up. In combination, the LCI and FEV capture a higher proportion of events with functional impairment.