Use of a comprehensive diagnostic algorithm for Anisakis allergy in a high seroprevalence Mediterranean setting

Background. Diagnosis of anisakis allergy (AA) is based on the skin prick test (SPT) and specific IgE (sIgE) determination. Anyway, false positivity cases are due to cross reactivity with numerous allergens. The aim of the study was to evaluate the reliability of a comprehensive diagnostic algorithm for the AA. Methods. An observational study was conducted on a sample of consecutive subjects accessing the allergology outpatient ambulatories of two hospitals located in Western Sicily. All the recruited outpatients were tested by Skin Prick Test performed using anisakis extracts by ALK-Abello (Madrid, Spain). Specific IgE dosage for anisakis extracts was then performed by using ImmunoCAP250 (Immunodiagnostics Uppsala, Sweden). Consequently, outpatients who tested positive to first line tests underwent sIgE testing for ascaris and tropomyosin. Lastly, outpatients positive to the first line were invited to be further tested by basophil activation test (BAT) by using Flow CAST kit and anisakis commercial extract (Buhlmann Laboratories AG, Schonenbuch, Switzerland), as confirmatory analysis. Results. One hundred and eleven outpatients with an anamnesis suggestive of sensitization to anisakis (AS) and 466 subjects with chronic urticaria (CU) were recruited in the study. Of these, 22 with AS and 41 with CU showed a sensitization to anisakis allergens. The diagnostic algorithm revealed that 8.8% of outpatients who tested positive to sIgE determination were affected by CU, while 82.5% of all the sIgE positivity was related to cross-reactivity. Overall, a genuine anisakis seroprevalence of 2.3% was documented. Within a sub-sample of 15 subjects with clinical symptoms related to AA, n. 8 showed a real positivity after BAT. A greater response to A. pegreffii allergens as compared to A. simplex was reported. Conclusions. Our preliminary findings support the high clinical specificity of BAT for AA diagnosis, suggesting implementing this method in a comprehensive diagnostic algorithm.