Lung clearance index is stable in most primary ciliary dyskinesia (PCD) patients managed in a specialist centre: A pilot study

Abstract

Introduction: PCD is rare; ciliary dysfunction causes inadequate mucociliary clearance in the lung leading to obstructive lung disease and bronchiectasis. Studies as to whether spirometry is stable or declines over time have been conflicting. Lung clearance index (LCI), derived from the multiple breath washout (MBW) test is a sensitive measure of lung function. We hypothesised LCI would remain stable over the medium term. Methods: 10 patients who had MBW 2009-10 were re-recruited in 2015 to perform the same investigations as previously, using sulphur hexafluoride tracer gas. LCI was calculated from MBW. 2 further patients had since died of respiratory disease. Results: There was overall no significant difference between results in 2010-2015. 9 patients had a minimal change in LCI over the 5 years (mean difference ±95%CI -0.23±1.23 ). One had a 63% improvement, following treatment for concurrent asthma. The 2 patients who had died had the highest LCIs in 2010. Conclusions: In this small cohort, there was no significant change in LCI over 5 years, supporting previous spirometry data. However, a very high LCI may be a bad prognostic sign, and LCI may be treatment-responsive. Although underpowered, these results may help inform sample size if LCI is to be used as an end-point in randomised controlled trials in mild-moderate PCD patients.