Molecular-based Allergy Diagnosis of Allergic Bronchopulmonary Aspergillosis in Aspergillus Fumigatus-sensitized Japanese Patients

Background: Distinguishing between patients with allergic bronchopulmonary aspergillosis (ABPA) and Aspergillus fumigatus (Af)-sensitized asthmatic patients without ABPA is sometimes difficult owing to the IgE-cross-reactivity between Af and other fungal allergens.

Objective: To establish the usefulness of molecular-based allergy diagnostics using allergen components from Af in distinguishing ABPA from Af-sensitized asthma without ABPA.

Methods: Sera from Japanese patients with ABPA (n = 53) and Af-sensitized asthma without ABPA (n = 253) were studied. The levels of IgE and IgG antibodies to allergen components from Af and IgE antibodies to different fugal allergen extracts were measured by ImmunoCAP. Comorbid atopic dermatitis (AD) was taken into consideration in the sensitization profile analysis.

Results: Patients with ABPA possessed significantly higher levels of IgE antibodies to Asp f 1, and Asp f 2 than asthmatic patients without ABPA. The areas under the receiver operating characteristic curves for the levels of IgE to Asp f 1 and Asp f 2 as diagnostic markers of ABPA were 0.75 and 0.78, respectively. The presence of IgE positivity to Asp f 1 and/or Asp f 2 resulted in increased sensitivity while losing little specificity. Comorbid AD was associated with higher levels of IgE to Asp f 6 (manganese superoxide dismutase from Af, a ubiquitous pan-allergen in fungi) and low but positive levels of IgE to other Af-components, which hampered the serological discrimination of ABPA.

Conclusions And Clinical Relevance: The levels of IgE to Asp f 1 and/or Asp f 2 can effectively differentiate ABPA from Af-sensitized asthma, suggesting that the amounts of IgE specific for these molecules are markers for genuine Af-sensitization in ABPA. However, comorbid AD must be taken into consideration in the interpretation of high IgE to Asp f 6. Establishing of IgE-sensitization profiles using panel of Af-allergen components provides valuable information for distinguishing genuine vs. cross-reactive sensitization in Af-sensitized patients.