title: Lung clearance index is a repeatable and sensitive indicator of radiological changes in bronchiectasis.
abstract: BACKGROUND
  In bronchiectasis there is a need for improved markers of lung function to determine disease severity and response to therapy.
  
  
  OBJECTIVE
  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).
  
  
  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 health-related 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.
authors.affiliation: 1 Centre for Infection and Immunity, Queen's University of Belfast, Belfast, United Kingdom.
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Rowan
authors.forename: Judy M
authors.initials: JM
authors.lastname: Bradley
authors.forename: Ian
authors.initials: I
authors.lastname: Bradbury
authors.forename: John
authors.initials: J
authors.lastname: Lawson
authors.forename: Tom
authors.initials: T
authors.lastname: Lynch
authors.forename: Per
authors.initials: P
authors.lastname: Gustafsson
authors.forename: Alex
authors.initials: A
authors.lastname: Horsley
authors.forename: Katherine
authors.initials: K
authors.lastname: O'Neill
authors.forename: Madeleine
authors.initials: M
authors.lastname: Ennis
authors.forename: J Stuart
authors.initials: JS
authors.lastname: Elborn
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001944:Breath Tests; D001987:Bronchiectasis / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000503:physiopathology; D005240:Feasibility Studies; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D011788:Quality of Life; D012372:ROC Curve; D012044:Regression Analysis; D012129:Respiratory Function Tests; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D013147:Spirometry; D011795:Surveys and Questionnaires; D014057:Tomography, X-Ray Computed / Q000379:methods; D055815:Young Adult