Usefulness of early serial measurement of specific and total immunoglobulin E in the diagnosis of gastro-allergic anisakiasis

Background Sensitization to Anisakis simplex (A, simplex) has been document ed to produce severe allergic reactions following ingestion of mainly raw o r under-cooked parasitized fish. False positive skin prick tests (SPT) or s pecific IgE against this nematode and cross-reactivity restricts diagnosis. Gastric anisakiasis and gastro-allergic anisakiasis occur if fish is paras itized by live A. simplex Objective To investigate if serial serological analysis could be useful in the diagnosis of acute parasitation by this nematode. Methods We included 41 patients who experienced an allergic reaction and/or abdominal symptoms after ingestion of raw or undercooked fish and displaye d specific IgE against A. simplex. Total and specific IgE were determined t wo times: in the 24-h period after onset of clinical symptoms and after 1 m onth. SPTs were performed against A. simplex and implicated fish. A fibre o ptic gastroscopy was performed in 22 patients. Results Median total IgE was 80.0 (Interquartile range [IQR] 41.5-186.5) kU /L in the first evaluation and 247.0 (IQR 96.5-649.5) kU/L after 1 month. M edian specific IgE against A. simplex was 11.4 (IQR 7.1-33.5) kU/L in the f irst 24 h and 36.8 (IQR 19.5-79.5) kU/L after 1 month. A rise of total IgE was observed in 35 of 41 patients (P < 0.00001) and a rise in specific IgE against A. simplex in 37 of 41 patients (P<0.00001). Mean percentage increm ent was 392% (215-571%; 95% confidence interval [CI]) for total IgE and 339 % (177-502%; 95% CI) for specific IgE. In nine of 22 gastroscopic examinati ons at least one larva, identified as A. simplex, could be detected by our microbiology service. In this group (n = 9) a rise of total and specific Ig E was detected in eight patients (89%) (P = 0.02). Conclusions We consider a rise of total and specific IgE in the first month after an allergic reaction as a useful tool in the diagnosis of gastro-all ergic anisakiasis (together with patient's history), even if the parasite c annot be seen with fibre optic gastroscopy. The important rise of total and specific IgE against A. simplex can be considered as a reaction induced by the live parasitizing larva in the context of a polyclonal immunological s timulation.