Comprehensive clinical study on cashew nut allergy: preliminary results

Background: Clinicians are seeing a growing number of cashew nut allergic patients. One of the peculiarities of this allergy is that a minimal amount of cashew nut allergen may cause severe allergic reactions, suggesting high potency of the allergen comparable to other tree nuts and peanuts. The double blind placebo controlled food challenge (DBPCFC) test is currently the gold standard to establish cashew nut allergy. The development of predictive tools in diagnosing cashew nut allergy is needed and research should be done on cross-sensitization between cashew nut and other botanically related allergens. Method: A Dutch multicenter, prospective study has been started to generate data for developing a multivariate predictive model for cashew nut allergy. The aim is to include two hundred children (aged 2-17 year) with sensitization to cashew nut. Also, these children have a history of positive reaction to cashew nut or an unknown reaction (because of never ingested).The results of clinical features, skin prick tests (SPT) and specific IgE with birch pollen, cashew nut, pistachio, hazelnut, mango and peanut will be analyzed. The children will also undergo a DBPCFC with cashew nut. Results: So far, 185 patients have been included and 170 analyzed. The mean age of the children was 8.7 year (range 2-17 year). Almost 75% (127) of the children had a positive DBPCFC and 39% reacted on dose 1 (1 mg cashew nut protein). Fifteen percent of the children had severe reactions during the DBPCFC. Most children had a combination of gastro-intestinal symptoms, skin symptoms, eye and upper airway symptoms. Mean SPT was 3.29 (HEP-index) and mean sIgE cashew was 19,79 (IE/l). One of the promising preliminary findings is that the results of SPT and sIgE seem to have predictive values for the outcome of the DBPCFC with cashew. Ninety-nine percent of co-sensitization was observed between cashew and pistachio, 74% with hazelnut, 81% with birch pollen, 72% with peanut and 39% with mango. Conclusion: Cashew nuts allergens are highly potent and may cause severe allergic reactions on a low dose. Most seen clinical features were of gastro-intestinal origin. sIgE and SPT results have predictive values for the outcome of the DBPCFC. Extreme high co-sensitization is seen between cashew nut and pistachio of which clinical relevance is unknown.