Study objectives: To clarify whether structural changes of the airway wall impair respiratory function in patients with mild asthma, and to determine whether mild asthma should be treated with inhaled steroids.
Setting: Showa University Hospital in Tokyo.
Patients: Thirteen healthy nonatopic volunteers (control subjects), 26 patients with mild asthma treated with a bronchodilator alone without oral or inhaled corticosteroids or antiallergic agents, and 10 patients with mild-to-moderate asthma treated with inhaled corticosteroids.
Measurements: We measured the thickness of the epithelial reticular basement membrane (Rbm) of the airway wall in bronchial biopsy specimens from patients with asthma and from healthy control subjects. We also performed spirometry and histamine challenge tests to evaluate airflow obstruction and airway hyperresponsiveness.
Results: The thickness of the Rbm in patients with mild asthma was significantly greater than that in healthy control subjects and was negatively correlated with the FEV1 as a percentage of FVC and the provocative concentration of histamine that caused a 20% decrease in FEV1 from the post-saline solution baseline value. Moreover, the Rbm was thicker in patients with mild asthma not treated with inhaled steroids than in patients with mild-to-moderate asthma treated with inhaled steroids.
Conclusions: The thickness of the Rbm is increased even in mild asthma and is correlated with airway obstruction and hyperresponsiveness. Our results suggests that anti-inflammatory treatment with inhaled steroids should be started in the early stage of bronchial asthma to prevent structural changes from occurring in the airway wall.