Aspergillus sensitization is associated with airflow limitation and bronchiectasis in severe asthma

Background: Abnormalities, including bronchiectasis, that are detectable on high-resolution computed tomography (HRCT) have been associated with severe asthma. Bronchiectasis is associated with the diagnosis of allergic bronchopulmonary aspergillosis (ABPA), which also occurs in patients with severe asthma. We sought to determine the frequency and pattern of HRCT abnormality and the relationship with Aspergillus fumigatus sensitization in one severe asthma population.

Methods: We examined our database of patients attending a supraregional severe asthma service (Manchester, UK). Clinical, physiological and immunological characteristics were compared between those with HRCT evidence of airway disease (specifically bronchiectasis) and those with no radiological abnormality.

Results: Of 133 patients analysed, 111 (83.4%) had an abnormal HRCT with bronchial wall thickening (41.3%), bronchiectasis (35.3%), air trapping (20.3%) and bronchial dilatation (16.5%) occurring most frequently. Radiological evidence of airway disease was associated with more obstructive spirometry (postbronchodilator FEV₁/FVC ratio 73.2%vs 64.8% [difference -8.5%, 95% CI -16.9 to -0.1, P = 0.048]). A. fumigatus sensitization was associated with a 2.01 increased hazard ratio of bronchiectasis (95% CI 1.26 to 3.22, P = 0.005), and more obstructive spirometry (postbronchodilator FEV₁/FVC ratio 57.6 vs 70.3 [difference -12.8, 95% CI -19.8 to -5.7, P = 0.001]). Patients with A. fumigatus sensitization had variable clinical and radiological characteristics that frequently did not conform to the conventional diagnostic criteria for ABPA.

Conclusion: Patients with severe asthma frequently have radiological abnormalities on HRCT. Sensitization to A. fumigatus is associated with bronchiectasis and greater airflow obstruction, even when diagnostic criteria for ABPA are not met.