Lung clearance index is a repeatable and sensitive indicator of radiological changes in bronchiectasis

Rationale: In bronchiectasis there is a need for improved markers of lung function to determine disease severity and response to therapy. Objectives: To assess whether the lung clearance index is a repeatable and more sensitive indicator of computed tomography (CT) scan abnormalities than spirometry in bronchiectasis. Methods: Thirty patients with stable bronchiectasis were recruited and lung clearance index, spirometry, and health-related quality of life measures were assessed on two occasions, 2 weeks apart when stable (study 1). A separate group of 60 patients with stable bronchiectasis was studied on a single visit with the same measurements and a CT scan (study 2). Measurements and Main Results: In study 1, the intervisit intraclass correlation coefficient for the lung clearance index was 0.94 (95% confidence interval, 0.89 to 0.97; P <0.001). In study 2, the mean age was 62 (10) years, FEV1 76.5% predicted (18.9), lung clearance index 9.1 (2.0), and total CT score 14.1 (10.2)%. The lung clearance index was abnormal in 53 of 60 patients (88%) and FEV1 was abnormal in 37 of 60 patients (62%). FEV1 negatively correlated with the lung clearance index (r = -0.51, P <0.0001). Across CT scores, there was a relationship with the lung clearance index, with little evidence of an effect of FEV1. There were no significant associations between the lung clearance index or FEV1 and healthrelated quality of life. Conclusions: The lung clearance index is repeatable and a more sensitive measure than FEV1 in the detection of abnormalities demonstrated on CT scan. The lung clearance index has the potential to be a useful clinical and research tool in patients with bronchiectasis.Copyright © 2014 by the American Thoracic Society.