Asthma diagnosis and treatmentRole of small airways in asthma: Investigation using high-resolution computed tomography
Section snippets
Subjects
We studied 29 patients with asthma diagnosed according to the American Thoracic Society criteria.24 At study entry, all patients were clinically stable and had not had disease exacerbations or respiratory infections for at least 1 month. Severity of asthma was mild persistent (step 2) in 10 patients, moderate persistent (step 3) in 13, and severe persistent (step 4) in 6.25 The quantitative index of asthma severity was defined according to this step classification (2, 3, or 4) of Global
Characteristics of patients with asthma
The characteristics of the subjects, including CT indices, are presented in Table I. On expiratory CT scans, LAA% decreased and MLD increased in all patients compared with the values on inspiratory scans (P < .0001 for both LAA% and MLD). All patients had received inhaled corticosteroids at daily doses equivalent to 800 μg (400-1600 μg) chlorofluorocarbon-beclomethasone dipropionate.
Relations between HRCT indices and clinical indices
Table II shows the coefficients of correlations between HRCT indices and clinical indices. All LAA% and MLD
Discussion
In the current study, we assessed LAA% and MLD on inspiratory and expiratory HRCT scans and calculated the expiratory/inspiratory ratios of these variables in patients with stable asthma. To our knowledge, this is the first study to examine the relations of lung density on CT with airway inflammation and airway responsiveness. Inspiratory LAA% and MLD weakly correlated only with FEV1/FVC. Expiratory LAA% and MLD more strongly correlated with FEV1/FVC, and the former also correlated with indices
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Disclosure of potential conflict of interest: The authors have declared that they have no conflict of interest.