title: Computed tomography structural lung changes in discordant airflow limitation.
abstract: BACKGROUND
  There is increasing evidence that structural lung changes may be present before the occurrence of airflow limitation as assessed by spirometry. This study investigated the prevalence of computed tomography (CT) quantified emphysema, airway wall thickening and gas trapping according to classification of airflow limitation (FEV1/FVC <70% and/or < the lower limit of normal (LLN)) in (heavy) smokers.
  
  
  METHODS
  A total number of 1,140 male former and current smokers participating in a lung cancer screenings trial (NELSON) were included and underwent chest CT scanning and spirometry. Emphysema was quantified by the 15(th) percentile, air way wall thickening by the square root of wall area for a theoretical airway with 10mm lumen perimeter (Pi10) and gas trapping by the mean lung density expiratory/inspiratory (E/I)-ratio. Participants were classified by entry FEV1/FVC: group 1>70%; group 2<70% but >LLN; and group 3<LLN. 32 restricted subjects, i.e. FEV1/FVC >70% but FEV1 <80% predicted, were excluded. Multivariate regression analysis correcting for covariates was used to asses the extent of emphysema, airway wall thickening and gas trapping according to three groups of airflow limitation.
  
  
  RESULTS
  Mean (standard deviation) age was 62.5 (5.2) years and packyears smoked was 41.0 (18.0). Group 2 subjects when compared to group 1 had a significantly lower 15(th) percentile, -920.6 HU versus -912.2 HU; a higher Pi10, 2.87 mm versus 2.57 mm; and a higher E/I-ratio, 88.6% versus 85.6% (all p<0.001).
  
  
  CONCLUSIONS
  Subjects with an FEV1/FVC<70%, but above the LLN, have a significant greater degree of structural lung changes on CT compared to subjects without airflow limitation.
authors.affiliation: Department of Respiratory Medicine, Division of Heart & Lungs, University Medical Center Utrecht, Utrecht, The Netherlands. fmohamedhoesein@gmail.com
authors.forename: Firdaus A A
authors.initials: FA
authors.lastname: Mohamed Hoesein
authors.forename: Pim A
authors.initials: PA
authors.lastname: de Jong
authors.forename: Jan-Willem J
authors.initials: JW
authors.lastname: Lammers
authors.forename: Willem Pthm
authors.initials: WP
authors.lastname: Mali
authors.forename: Michael
authors.initials: M
authors.lastname: Schmidt
authors.forename: Harry J
authors.initials: HJ
authors.lastname: de Koning
authors.forename: Carlijn
authors.initials: C
authors.lastname: van der Aalst
authors.forename: Matthijs
authors.initials: M
authors.lastname: Oudkerk
authors.forename: Rozemarijn
authors.initials: R
authors.lastname: Vliegenthart
authors.forename: Bram
authors.initials: B
authors.lastname: van Ginneken
authors.forename: Eva M
authors.initials: EM
authors.lastname: van Rikxoort
authors.forename: Pieter
authors.initials: P
authors.lastname: Zanen
mesh_terms: D000368:Aged; D000402:Airway Obstruction / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000503:physiopathology; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D012129:Respiratory Function Tests; D012907:Smoking; D014057:Tomography, X-Ray Computed