Detection of Anisakis simplex‐induced basophil activation by flow cytometry

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Abstract
Background: Laboratory diagnosis of anisakidosis is based on specific serum IgE detection. Recently, detection of allergen‐induced basophil activation by flow cytometry has been proposed as a valuable tool for allergy diagnosis. Objective: To evaluate if detection of Anisakis‐induced basophil activation by flow cytometry is a useful tool in the diagnosis of Anisakis allergy. Methods: Patients with Anisakis allergy (A.s.+, n = 37), patients reporting chronic urticaria or abdominal pain unrelated to fish ingestion (A.s.−, n = 51), and healthy controls (n = 12) were studied. Specific IgE to Anisakis simplex (A. simplex) was quantified with CAP‐FEIA method, and basophil activation test was performed with three different concentrations of an Anisakis crude extract. Basophil gating was performed with CD123 and HLA‐DR, and cellular activation was measured with CD63. Results: A.s.+ patients showed significantly higher age and total IgE levels than did the A.s.− patients. Specific IgE to A. simplex correlated with the activated basophil percentages obtained with 15 μg/mL (r = 0.80; P < 0.001), 1.5 μg/mL (r = 0.84; P < 0.001), and 0.15 μg/mL (r = 0.82; P < 0.001) of A. simplex crude extract. Nine individuals (3 in the A.s.+ group and 6 in the A.s.− group) were nonresponders to basophil stimulation with anti‐IgE. Five A.s.− patients showed positive IgE values to A. simplex while the basophil activation test was negative. According to the receiver operating characteristics curves performed between A.s.+ vs. A.s.− and A.s.+ vs. healthy controls, the cutoff for a positive basophil activation test was ≥21% (specificity = 96%, sensitivity = 100%), and 16% (sensitivity and specificity of 100%) respectively. When nonresponders were included in the A.s.+ vs. A.s.− analysis, sensitivity decreased to 95%. Multivariate logistic analysis showed that the specific basophil activation was a factor independently associated with clinical symptoms of A. simplex allergy. Conclusions: Detection of A. simplex‐induced basophil activation by flow cytometry is a useful laboratory technique for the diagnosis of anisakidosis, supplementing specific IgE determinations.

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