S44 Lung clearance index (LCI) and FEV1 correlate equally with treatment burden as measured by cystic fibrosis questionnaire-revised (CFQ-R)

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LCI derived from multiple breath washout (MBW), measures the elimination of an inert marker gas during tidal breathing and is a sensitive measure of ventilation inhomogeneity in CF. LCI is more sensitive than FEV1 and FEF25−75 in detecting airways abnormalities and does not require a forced manoeuvre. The CFQ-R is a validated patient reported outcome used to assess health related quality of life (HRQoL) and patient perception of symptoms. There is a need to better understand the relationship between LCI, HRQoL and symptoms.


To investigate the relationship between LCI, FEV1 % pred, HRQoL and symptoms as measured by the CFQ-R.


These data are part of a larger study investigating the role of LCI as a tool to monitor lung function longitudinally. Patients were recruited from the adult and paediatric CF centres in Belfast Health and Social Care Trust. Inclusion criteria: clinical diagnosis of CF; clinically stable (exacerbation free=4 weeks); informed consent. Age appropriate versions of the CFQ-R were used (patients >14 years, children aged 12 and 13, children aged 6–11). A parent questionnaire was completed in addition where appropriate (for children aged 6–13). The instrument yielded a score of 0–100 for each domain, with higher numbers indicating better function on various domains. Participants completed three MBW tests, using 0.2% sulphur hexafluoride and a modified Innocor device. LCI was reported as the mean of at least 2 acceptable tests. Spirometry was performed to ATS/ERS standards.


Data were collected for 21 patients (15M:6F), age range 6–51 yrs, mean (SD) 26.4 (13.7). Mean (SD) FEV1 % pred was 77.1 (16.3). Mean (SD) LCI was 9.4 (2.5) (normal <7.5). LCI correlated negatively with FEV1% pred (r=−0.62 p=0.003). The domain of treatment burden was significantly correlated with LCI (r=−0.67 p=0.001) and FEV1% pred (r=0.69 p=0.001). However no correlation was observed with respiratory symptoms or any other domain of the CFQ-R.


Patients with a greater treatment burden are more likely to have more severe lung disease. The severity of CF lung disease as determined by FEV1% pred and LCI correlate equally with treatment burden. This further validates LCI as a useful measure of lung function.

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