title: Qualitative analysis of high-resolution CT scans in severe asthma.
abstract: BACKGROUND
  High-resolution CT (HRCT) scanning is part of the management of severe asthma, but its application varies between centers. We sought to describe the HRCT scan abnormalities of a large severe asthma cohort and to determine the utility of clinical features to direct the use of HRCT scanning in this group of patients.
  
  
  METHODS
  Subjects attending our Difficult Asthma Clinic (DAC) between February 2000 and November 2006 (n = 463) were extensively re-characterized and 185 underwent HRCT scan. The HRCT scans were analyzed qualitatively and the interobserver variability was assessed. Using logistic regression we defined clinical parameters that were associated with bronchiectasis (BE) and bronchial wall thickening (BWT) alone or in combination.
  
  
  RESULTS
  HRCT scan abnormalities were present in 80% of subjects and often coexisted with BWT (62%), BE (40%), and emphysema (8%). The interobserver agreement for BE (kappa = 0.76) and BWT (kappa = 0.63) was substantial. DAC patients who underwent HRCT scanning compared with those who did not were older, had longer disease duration, had poorer lung function, were receiving higher doses of corticosteroids, and had increased neutrophilic airway inflammation. The sensitivity and specificity of detecting BE clinically were 74% and 45%, respectively. FEV(1)/FVC ratio emerged as an important predictor for both BE and BWT but had poor discriminatory utility for subjects who did not have airway structural changes (FEV(1)/FVC ratio, >or= 75%; sensitivity, 67%; specificity, 65%).
  
  
  CONCLUSIONS
  HRCT scan abnormalities are common in patients with severe asthma. Nonradiologic assessments fail to reliably predict important bronchial wall changes; therefore, CT scan acquisition may be required in all patients with severe asthma.
authors: Institute for Lung Health, University of Leicester, Leicester, UK.
authors: Sumit
authors: S
authors: Gupta
authors: Institute for Lung Health, University of Leicester, Leicester, UK.
authors: Salman
authors: S
authors: Siddiqui
authors: Institute for Lung Health, University of Leicester, Leicester, UK.
authors: Pranab
authors: P
authors: Haldar
authors: Glenfield Hospital, Leicester, UK.
authors: J Vimal
authors: JV
authors: Raj
authors: Glenfield Hospital, Leicester, UK.
authors: James J
authors: JJ
authors: Entwisle
authors: Institute for Lung Health, University of Leicester, Leicester, UK.
authors: Andrew J
authors: AJ
authors: Wardlaw
authors: Institute for Lung Health, University of Leicester, Leicester, UK.
authors: Peter
authors: P
authors: Bradding
authors: Institute for Lung Health, University of Leicester, Leicester, UK.
authors: Ian D
authors: ID
authors: Pavord
authors: Institute for Lung Health, University of Leicester, Leicester, UK.
authors: Ruth H
authors: RH
authors: Green
authors: Institute for Lung Health, University of Leicester, Leicester, UK. Electronic address: ceb17@le.ac.uk.
authors: Christopher E
authors: CE
authors: Brightling
mesh_terms: D000328:Adult; D001249:Asthma / Q000000981:diagnostic imaging* / Q000503:physiopathology; D001987:Bronchiectasis / Q000000981:diagnostic imaging* / Q000503:physiopathology; D003430:Cross-Sectional Studies; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D016015:Logistic Models; D008168:Lung / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011237:Predictive Value of Tests; D012372:ROC Curve; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014797:Vital Capacity / Q000502:physiology