Abstract
The lung clearance index (LCI) has strong intra-test repeatability; however, the inter-test reproducibility of the LCI is poorly defined.
The aim of the present study was to define a physiologically meaningful change in LCI in preschool children, which discriminates changes associated with disease progression from biological variability.
Repeated LCI measurements from a longitudinal cohort study of children with cystic fibrosis and age-matched controls were collected to define the inter-visit reproducibility of the LCI. Absolute change, the coefficient of variation, Bland–Altman limits of agreement, the coefficient of repeatability, intra-class correlation coefficient, and percentage changes were calculated.
LCI measurements (n=505) from 71 healthy and 77 cystic fibrosis participants (aged 2.6–6 years) were analysed. LCI variability was proportional to its magnitude, such that reproducibility defined by absolute changes is biased. A physiologically relevant change for quarterly LCI measurements in health was defined as exceeding ±15%. In clinically stable cystic fibrosis participants, the threshold was higher (±25%); however, for measurements made 24 h apart, the threshold was similar to that observed in health (±17%).
A percentage change in LCI greater than ±15% in preschool children can be considered physiologically relevant and greater than the biological variability of the test.
Abstract
Biological variability of lung clearance index is dependent on magnitude; % change is better for tracking patients http://ow.ly/tgbX30dBbCX
Footnotes
Support statement: This study was funded by the National Heart, Lung, and Blood Institute, grant number R01HL116232-04. Funding information for this article has been deposited with the Crossref Funder Registry.
Conflict of interest: None declared.
- Received February 28, 2017.
- Accepted July 6, 2017.
- Copyright ©ERS 2017
This ERJ Open article is open access and distributed under the terms of the Creative Commons Attribution Non-commercial Licence 4.0