Lung Clearance Index to Track Acute Respiratory Events in School-Age Children with Cystic Fibrosis
Lucy Perrem, Sanja Stanojevic, Michelle Shaw, Renée Jensen, Nancy McDonald, Sarah Isaac, Miriam Davis, Charles Clem, Julia Guido, Sylvia Jara, Lisa France, Melinda Solomon, Hartmut Grasemann, Valerie Waters, Neil Sweezey, Don B. Sanders, Stephanie D. Davis, Félix Ratjen
Abstract
Abstract Rationale 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. Objectives To describe changes in LCI with acute respiratory events in school-age children with CF. Methods In a multisite prospective observational study, the LCI and FEV1 were measured quarterly and during acute respiratory events. Linear regression was used to compare relative changes in LCI and FEV1% predicted at acute respiratory events. Logistic regression was used to compare the odds of a significant worsening in LCI and FEV1% predicted at acute respiratory events. Generalized estimating equation models were used to account for repeated events in the same subject. Measurements and Main Results 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 FEV1% 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 FEV1% predicted (41.7% vs. 30.0%; P = 0.012); 53.9% of events were associated with worsening in LCI or FEV1. Neither LCI nor FEV1 recovered to baseline values at the next follow-up visit. Conclusions 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 FEV1 capture a higher proportion of events with functional impairment.