Detection of Anisakis simplex-induced basophil activation by flow cytometry

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 mu g/mL (r = 0.80; P < 0.001), 1.5 mu g/mL (r = 0.84; P < 0.001), and 0.15 mu g/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. (c) 2005 International Society for Analytical Cytology.