Basophil Activation Test With Aspergillus Molecules: The Case for ABPA.

Background: Allergic bronchopulmonary aspergillosis (ABPA) is an underestimated allergic disease due to Aspergillus fumigatus (AF). The main diagnostic criteria for ABPA rely on the evaluation of immunoglobulin (Ig) E and IgG responses to AF extracts, although these cannot discriminate AF-sensitization from ABPA. Objectives: To evaluate the performance of cellular functional assays with extract and molecular AF allergens in ABPA. Methods: A prospective cohort of 67 patients (6 ABPA) was investigated with basophil activation test (BAT) with AF extract. Twelve patients were further investigated for BAT responses to molecular AF components: Asp f 1, Asp f 2, Asp f 3, Asp f 4, and Asp f 6. Results: BAT with AF extract with an optimized cutoff displayed 100% sensitivity and 77.6% specificity for ABPA diagnosis. Among patients with positive BAT to AF, BAT with Asp f 4 was significantly higher in ABPA patients at 10 ng/mL (mean basophil stimulation index 10.56 in ABPA vs. 1.24 in non-ABPA patients, p = 0.0002). Conclusion: BAT with AF is a promising diagnostic biomarker in the context of suspected ABPA, which can be further improved with AF molecular allergens, especially Asp f 4.