Background Lung clearance index (LCI) is a promising lung function outcome in individuals with primary ciliary dyskinesia (PCD). The impact of events clinically important for individuals with PCD, such as pulmonary exacerbations, on LCI is unknown.
Methods We conducted an international, multicentre, observational cohort study to assess the association of LCI and risk of pulmonary exacerbation, specific changes in LCI during pulmonary exacerbation and global variability of LCI across four visits every 4 months. Ninety individuals with PCD, aged 3–41 years, underwent nitrogen multiple-breath washout (MBW) and spirometry measurements. The association of LCI and pulmonary exacerbations was assessed by Cox proportional hazards and random-effects regression models.
Results We obtained 430 MBW and 427 spirometry measurements. In total, 379 person-years at risk contributed to the analysis. Per one unit increase (deterioration) in LCI, the risk of future pulmonary exacerbation increased by 13%: HR (95% CI), 1.13 (1.04 to 1.23). If LCI changed from a range of values considered normal to abnormal, the risk of future pulmonary exacerbations increased by 87%: 1.87 (1.08 to 3.23). During pulmonary exacerbations, LCI increased by 1.22 units (14.5%). After pulmonary exacerbations, LCI tended to decline. Estimates of variability in LCI suggested lower variation within individuals compared with variation between individuals. Findings were comparable for forced expiratory volume in 1 s.
Conclusion On a visit-to-visit basis, LCI measurement may add to the prediction of pulmonary exacerbations, the assessment of lung function decline and the potential lung function response to treatment of pulmonary exacerbations.
- primary ciliary dyskinesia
- lung physiology
- paediatric lung disease
- respiratory infection
Data availability statement
Data are available upon reasonable request. Data are available upon reasonable request.
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FS and AS contributed equally.
MB and CK-R contributed equally.
Contributors All authors drafted and approved the final version of the manuscript. FS, AS, MB and CKR were the lead authors with overall responsibility for the manuscript.
Funding MB and CKR participate in the Better Evidence to Advance Therapeutic Options for PCD (BEAT-PCD) network (COST action BM 1407). MB is supported by an unrestricted postdoctoral research grant from KOOR, University Hospital Leuven, Belgium. AS is supported by an unrestricted research grant from FoRUM, Ruhr-University Bochum.
Competing interests Relevant financial activities for this work: AS reports grant from Ruhr-University Bochum, payment to institution. MB reports postdoctoral grant KOOR from UZLeuven, payment to institution. Relevant financial activities outside the work: FS has grants/grants pending from LungenLiga Bern, CFCH, and payment for lectures from Vertex, Novartis. MB is a member of the European Reference Network for Rare Respiratory Diseases (ERN-LUNG) Project ID No 739546. She has grants/grants pending from Horizon 2020, MyCyFAPP.
Provenance and peer review Not commissioned; externally peer reviewed.
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