Lung clearance index and structural lung disease on computed tomography in early cystic fibrosis

Abstract

Rationale: The lung clearance index is a measure of ventilation distribution derived from the multiple-breath washout technique. It has been suggested as a surrogate for chest computed tomography to detect structural lung abnormalities in individuals with cystic fibrosis (CF); however, the associations between lung clearance index and early structural lung disease are unclear. Objectives: We assessed the ability of the lung clearance index to reflect structural lung disease on the basis of chest computed tomography across the entire pediatric age range. Methods: Lung clearance index was assessed in 42 infants (ages 0–2 yr), 39 preschool children (ages 3–6 yr), and 38 school-age children (7–16 yr) with CF before chest computed tomography and in 72 healthy control subjects. Scans were evaluated for CF-related structural lung disease using the Perth-Rotterdam Annotated Grid Morphometric Analysis for Cystic Fibrosis quantitative outcome measure. Measurements and Main Results: In infants with CF, lung clearance index is insensitive to structural disease (κ = −0.03 [95% confidence interval, −0.05 to 0.16]). In preschool children with CF, lung clearance index correlates with total disease extent. In school-age children, lung clearance index correlates with extent of total disease, bronchiectasis, and air trapping. In preschool and school-age children, lung clearance index has a good positive predictive value (83–86%) but a poor negative predictive value (50–55%) to detect the presence of bronchiectasis. Conclusions: These data suggest that lung clearance index may be a useful surveillance tool to monitor structural lung disease in preschool and school-age children with CF. However, lung clearance index cannot replace chest computed tomography to screen for bronchiectasis in this population.