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 (k = 20.03 [95% confidence interval, 20.05 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.

Authors: Kathryn A. Ramsey, Tim Rosenow, Lidija Turkovic, Billy Skoric, Georgia Banton, Anne-Marie Adams, Shannon J. Simpson, Conor Murray, Sarath C. Ranganathan, Stephen M. Stick and Graham L. Hall on behalf of AREST CF.

Published in the American Journal of Respiratory and Critical Care Medicine in January 2016.