Abstract
Background: Asthma comprises heterogeneous inflammatory airway disorders whose classification has not been established. Quantitative computed tomography (QCT) methods can differentiate lung disease using accurate assessment of location, extent, and severity of the disease. This study aimed to identify heterogeneous asthmatic groups by QCT metrics of airway and parenchymal structure, which is associated with radiologists’ visual analysis and bronchodilator responses in a prospective design.Methods: Using the input from QCT-based metrics, including hydraulic diameter (Dh), luminal wall thickness (WT), functional small airway disease (fSAD), and emphysematous lung (Emph), a cluster analysis was performed and compared with grouping based on site of airway involvement and remodeling evaluated by radiologists.Results: 61 asthmatics were grouped into four clusters with different clinical severities. From C1 to C4, more severe lung function deterioration, higher fixed obstruction rate, and more frequent asthma exacerbation in 5-year follow-up were observed. C1 presented non-severe asthma with increased WT, Dh of proximal airways, and fSAD. C2 was mixed with non-severe and severe asthma, which had reserved bronchodilator responses of proximal airways. C3 and C4 presented severe asthmatics that exhibited reduced Dh of proximal airway and its bronchodilator responsiveness; C3 was severe allergic asthma without fSAD, while C4 was ex-smokers with significantly high fSAD% and Emph%. These clusters were correlated with the grouping by radiologists and their clinical outcomes.Conclusions: Four QCT imaging-based clusters with distinct structural and functional changes in proximal and small airways can stratify heterogeneous asthmatics and may serve as complementary tools for predicting future asthma outcomes.
Quantitative computed tomography measurements to evaluate airway disease in chronic obstructive pulmonary disease: Relationship to physiological measurements, clinical index and visual assessment of airway disease
