Lung clearance index and high-resolution computed tomography scores in primary ciliary dyskinesia

Abstract

Rationale: Lung clearance index (LCI) is a more sensitive measure of lung function than spirometry in cystic fibrosis (CF) and correlates well with abnormalities in high-resolution computed tomography (HRCT) scanning. We hypothesized LCI would be equally sensitive to lung disease in primary ciliary dyskinesia (PCD).

Objectives: To test the relationships between LCI, spirometry, and HRCT in PCD and to compare them to the established relationships in CF.

Methods: Cross-sectional study of 127 patients with CF and 33 patients with PCD, all of whom had spirometry and LCI, of which a subset of 21 of each had HRCT performed. HRCT was scored for individual features and these features compared with physiological parameters.

Measurements and main results: Unlike in CF, and contrary to our hypothesis, there was no correlation between spirometry and LCI in PCD and no correlation between HRCT features and LCI or spirometry in PCD.

Conclusions: We show for the first time that HRCT, spirometry, and LCI have different relationships in different airway diseases and that LCI does not appear to be a sensitive test of airway disease in advanced PCD. We hypothesize that this results from dissimilarities between the components of large and small airway disease in CF and PCD. These differences may in part lead to the different prognosis in these two neutrophilic airway diseases.

Figure 1.

(a) FEV₁ versus lung clearance index (LCI) in the full primary ciliary dyskinesia cohort. There is no significant relationship seen (P = 0.081, r = −0.31, n = 33). Dotted lines represent the upper (LCI) and lower (FEV₁) limits of normal for both measures. (b) FEV₁ versus LCI in the full cystic fibrosis (CF) cohort. The two are strongly correlated (P < 0.0001, r = −0.60, n = 127). LCI shows a superior sensitivity in patients with CF compared with FEV₁. Thirty-five patients have an abnormal LCI while still having normal spirometry, compared with the seven having an abnormal FEV₁ and normal LCI.

Figure 2.

(a) Midexpiratory flow between 25 and 75% of vital capacity (MEF_25–75%) is correlated with lung clearance index (LCI) in primary ciliary dyskinesia (P = 0.001, r = −0.5). (b) MEF_25–75% is correlated with LCI in cystic fibrosis (P < 0.0001, r = −0.6).