Sensitization to Anisakis simplex: prevalence in an allergy outpatient clinic of Madrid (Spain)

Background: Anisakis simplex is a nematode that has been implicated in IgE-mediated allergic episodes. The aim of this study was to determine the prevalence of clinical and subclinical sensitization to A. simplex in adults attending an allergy outpatient clinic in Madrid (Spain), as well as to assess clinical and laboratory data related to the diagnosis of A. simplex allergy. Methods: We have investigated the alimentary habits (fish ingestion) and the presentation of associated acute or chronic gastrointestinal symptoms in 87 patients referred to our Allergy Outpatient Clinic because of various pathologic conditions. Skin prick tests were performed with an A. simplex extract, and the total and specific (to this parasite) serum IgE levels were measured (CAP-FEIA). Results: Clinical and subclinical sensitization to A. simplex was found in 5.7% and 23% of the patients, respectively. The skin tests and the CAP were positive to A. simplex in 16% and 22% of the patients, respectively, but the two techniques were simultaneously positive in only 9% of the cases. Forty-four per cent of the patients who had sought medical care because of urticaria, angioedema or anaphylaxis of undetermined aetiology showed a positive CAP assay to A. simplex, as compared to 17% of those with other reasons for requesting medical consultation (p<0.01). There were no statistically significant differences between the two groups in regard to the results of the skin prick tests. The alimentary habits in the patients with positive skin prick tests and/or positive CAP assay were not significantly different from those of the patients with negative results. Conclusions. A high proportion of clinical and subclinical sensitization to A. simplex has been detected among patients attending an outpatient allergy clinic in Madrid (Spain). A discrepancy was detected between the skin prick tests and CAP assay results. A habit of fish ingestion and recurrent gastrointestinal episodes do not appear to be associated with a higher frequency of subclinical A. simplex sensitization. The association between chronic and acute recurrent urticaria and the finding of specific serum IgE antibodies to the parasite deserves further study.