Assessment of airway remodeling by HRCT in asthmatic patients: correlation with age, smoking, disease duration and severity

Rationale: Healing that may lead to structural changes known as airway remodeling follows chronic inflammation of the airways. To date, airway remodeling has only been assessed using histological examination of airways. However, it may now be possible to assess and quantify the extent of airway remodeling in vivo using high-resolution CT (HRCT). Aim of Work: To prospectively evaluate airway wall thickness as an indicator of remodeling by using thin section HRCT in patients with asthma, and to correlate these CT findings with pulmonary function tests (PFTs) results and other clinical indices in asthmatics. Methods: Forty-one patients with asthma and 20 healthy control subjects took part in the study. Remodeling as measured by the whole airway wall thickness was assessed with HRCT scanning after pretreatment with oral steroids for 2 weeks and inhaled β2 agonist to minimize reversible changes of the airway walls. Thickness-to diameter ratio (TDR) and the percentage wall area (PWA) were determined. Spirometric tests were also performed. Results: TDR and PWA were significantly higher inpatients with asthma than in healthy subjects. Both TDR and PWA were strongly correlated with disease severity and disease duration. Moreover, these two indices of airway wall thickness were inversely correlated with the percentage of predicted forced vital capacity (FVC%), forced expiratory volume in 1 second (FEV1%) and FEV1/FVC ratio and post- broncho-dilator reversibility in patients with asthma. Conclusions: These findings indicate that HRCT is useful non- invasive method for assessment of airway wall thickness and remodeling which can cause irreversible airflow obstruction in patients with asthma. The airway wall thickening occurs more in-patients with moderate and severe asthma. The degree of airway wall thickening is related to the duration and severity of disease and degree of airflow obstruction.