title: Relationship between lung function and quantitative computed tomographic parameters of airway remodeling, air trapping, and emphysema in patients with asthma and chronic obstructive pulmonary disease: A single-center study.
abstract: There is a paucity of studies comparing asthma and chronic obstructive pulmonary disease (COPD) based on thoracic quantitative computed tomographic (QCT) parameters.
  
  
  
  We sought to compare QCT parameters of airway remodeling, air trapping, and emphysema between asthmatic patients and patients with COPD and explore their relationship with airflow limitation.
  
  
  
  Asthmatic patients (n = 171), patients with COPD (n = 81), and healthy subjects (n = 49) recruited from a single center underwent QCT and clinical characterization.
  
  
  
  Proximal airway percentage wall area (%WA) was significantly increased in asthmatic patients (62.5% [SD, 2.2]) and patients with COPD (62.7% [SD, 2.3]) compared with that in healthy control subjects (60.3% [SD, 2.2], P < .001). Air trapping measured based on mean lung density expiratory/inspiratory ratio was significantly increased in patients with COPD (mean, 0.922 [SD, 0.037]) and asthmatic patients (mean, 0.852 [SD, 0.061]) compared with that in healthy subjects (mean, 0.816 [SD, 0.066], P < .001). Emphysema assessed based on lung density measured by using Hounsfield units below which 15% of the voxels lie (Perc15) was a feature of COPD only (patients with COPD: mean, -964 [SD, 19.62] vs asthmatic patients: mean, -937 [SD, 22.7] and healthy subjects: mean, -937 [SD, 17.1], P < .001). Multiple regression analyses showed that the strongest predictor of lung function impairment in asthmatic patients was %WA, whereas in the COPD and asthma subgrouped with postbronchodilator FEV1 percent predicted value of less than 80%, it was air trapping. Factor analysis of QCT parameters in asthmatic patients and patients with COPD combined determined 3 components, with %WA, air trapping, and Perc15 values being the highest loading factors. Cluster analysis identified 3 clusters with mild, moderate, or severe lung function impairment with corresponding decreased lung density (Perc15 values) and increased air trapping.
  
  
  
  In asthmatic patients and patients with COPD, lung function impairment is strongly associated with air trapping, with a contribution from proximal airway narrowing in asthmatic patients.
authors.affiliation: Department of Infection, Inflammation and Immunity and Health Sciences, Institute for Lung Health, University of Leicester, Leicester, United Kingdom.
authors.forename: Ruth A
authors.initials: RA
authors.lastname: Hartley
authors.affiliation: Department of Infection, Inflammation and Immunity and Health Sciences, Institute for Lung Health, University of Leicester, Leicester, United Kingdom.
authors.forename: Bethan L
authors.initials: BL
authors.lastname: Barker
authors.affiliation: Department of Infection, Inflammation and Immunity and Health Sciences, Institute for Lung Health, University of Leicester, Leicester, United Kingdom.
authors.forename: Chris
authors.initials: C
authors.lastname: Newby
authors.affiliation: Department of Infection, Inflammation and Immunity and Health Sciences, Institute for Lung Health, University of Leicester, Leicester, United Kingdom.
authors.forename: Mini
authors.initials: M
authors.lastname: Pakkal
authors.affiliation: Department of Infection, Inflammation and Immunity and Health Sciences, Institute for Lung Health, University of Leicester, Leicester, United Kingdom.
authors.forename: Simonetta
authors.initials: S
authors.lastname: Baldi
authors.affiliation: Department of experimental Medicine, Hoffmann-La Roche, Nutley, NJ.
authors.forename: Radhika
authors.initials: R
authors.lastname: Kajekar
authors.affiliation: Novartis, Basel, Switzerland.
authors.forename: Richard
authors.initials: R
authors.lastname: Kay
authors.affiliation: Novartis, Basel, Switzerland.
authors.forename: Marie
authors.initials: M
authors.lastname: Laurencin
authors.affiliation: GlaxoSmithKline, Stevenage, United Kingdom.
authors.forename: Richard P
authors.initials: RP
authors.lastname: Marshall
authors.affiliation: GlaxoSmithKline, Stevenage, United Kingdom.
authors.forename: Ana R
authors.initials: AR
authors.lastname: Sousa
authors.affiliation: Department of experimental Medicine, Hoffmann-La Roche, Nutley, NJ.
authors.forename: Harsukh
authors.initials: H
authors.lastname: Parmar
authors.affiliation: Department of Infection, Inflammation and Immunity and Health Sciences, Institute for Lung Health, University of Leicester, Leicester, United Kingdom.
authors.forename: Salman
authors.initials: S
authors.lastname: Siddiqui
authors.affiliation: Department of Infection, Inflammation and Immunity and Health Sciences, Institute for Lung Health, University of Leicester, Leicester, United Kingdom; Radiology Department, Glenfield Hospital, University Hospitals of Leicester NHS Trust, Leicester, United Kingdom.
authors.forename: Sumit
authors.initials: S
authors.lastname: Gupta
authors.affiliation: Department of Infection, Inflammation and Immunity and Health Sciences, Institute for Lung Health, University of Leicester, Leicester, United Kingdom. Electronic address: ceb17@le.ac.uk.
authors.forename: Chris E
authors.initials: CE
authors.lastname: Brightling
mesh_terms: D000328:Adult; D000368:Aged; D056151:Airway Remodeling; D001249:Asthma / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D011656:Pulmonary Emphysema / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D014057:Tomography, X-Ray Computed
keywords: Asthma; airway remodeling; asthma-COPD overlap syndrome; chronic obstructive pulmonary disease; emphysema; gas trapping; quantitative computed tomography; small airway disease