title: Low attenuation area is associated with airflow limitation and airway hyperresponsiveness.
abstract: BACKGROUND
  Asthma is a chronic inflammatory disorder of the airways characterized by airflow limitation and airway hyperresponsiveness. Lung density indices on quantitative computed tomography (QCT) are assumed to reflect the degree of air trapping originated from airflow limitation in airway diseases.
  
  
  OBJECTIVE
  The present study investigated the availability of lung density indices on QCT in clinical evaluation of asthma.
  
  
  METHODS
  Eleven asthmatic patients and 48 healthy control subjects were prospectively evaluated by QCT, pulmonary function testing, and a methacholine challenge test. High-resolution computed tomography scans were performed at full-inspiratory and full-expiratory phases, and percentage of lung field occupied by low attenuation area (LAA%) and mean lung density (MLD) at both inspiratory and expiratory phases were measured.
  
  
  RESULTS
  MLD values at inspiratory phase were significantly increased in asthmatic patients compared with those in healthy control subjects. Inspiratory LAA% values were significantly decreased in asthmatics compared with the values in control subjects. On expiratory scans, MLD values of asthmatics were significantly lower than the values of control subjects. Expiratory LAA% values of asthmatics were significantly higher than the values of control subjects. The LAA% in the expiratory phase showed significant negative correlation with forced expiratory volume in 1 second (FEV(1)), FEV(1)/forced vital capacity, and the provocative dose of methacholine causing a 20% decrease in FEV(1) in asthmatic patients.
  
  
  CONCLUSIONS
  These results suggest that lung density indices on QCT may be useful for clinical evaluation of asthmatic patients and increased LAA% in the expiratory phase is associated with airflow limitation and airway hyperresponsiveness in asthma.
authors.affiliation: Department of Internal Medicine and Airway Remodeling Laboratory, Chonbuk National University Medical School, Deokjin-Gu, Jeonju, South Korea.
authors.forename: Ka Young
authors.initials: KY
authors.lastname: Lee
authors.forename: Seoung Ju
authors.initials: SJ
authors.lastname: Park
authors.forename: So Ri
authors.initials: SR
authors.lastname: Kim
authors.forename: Kyung Hoon
authors.initials: KH
authors.lastname: Min
authors.forename: Yeong Hun
authors.initials: YH
authors.lastname: Choe
authors.forename: Gong Yong
authors.initials: GY
authors.lastname: Jin
authors.forename: Yong Chul
authors.initials: YC
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000403:Airway Resistance / Q000502:physiology*; D001249:Asthma / Q000503:physiopathology*; D016535:Bronchial Hyperreactivity / Q000503:physiopathology*; D045853:Exhalation / Q000502:physiology; D005260:Female; D006801:Humans; D001239:Inhalation / Q000502:physiology; D008168:Lung / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D012129:Respiratory Function Tests; D014057:Tomography, X-Ray Computed; D055815:Young Adult