Background: The incidence of cashew nut anaphylaxis is increasing and there is a need for accurate diagnostic tests. Age-specific cutoffs in children are lacking. Changes in serum tryptase levels are not well documented in pediatric food allergy, except in anaphylaxis. Objective: To evaluate the ability of various tests to diagnose cashew nut allergy and to predict reaction severity. We also investigated changes in tryptase and their correlation to reaction severity. Methods: We performed an open cashew nut challenge on 106 children (aged 1-16 years), who were sensitized to cashew nut with either previous allergic reaction to cashew nut or no known exposure. We analyzed the accu-racy of Ana o 3 immunoglobulin E (IgE), cashew nut IgE, skin prick test, basophil activation test (BAT), and combi-nations thereof to diagnose cashew nut allergy and to predict reaction severity. Tryptase level was measured at the baseline and during an allergic reaction. Results: A total of 72 children had positive challenge outcomes. Ana o 3 IgE seemed to be the best single test to diagnose cashew allergy, with a 0.97 kU/L cutoff exhibiting 94.1 specificity and 61.1 sensitivity. Though BAT values of at least 22.8 best predicted reaction severity, with 91.7 specificity and 60.7 sensitivity, the cutoffs were age-specific. Tryptase levels increased substantially 1 to 2 hours after the first allergic symptoms compared with baseline. Conclusion: Ana o 3 IgE seems to be the best diagnostic test in pediatric cashew nut allergy, and test combina-tions do not seem to improve the diagnostics. Cutoffs are age-specific. BAT is promising in predicting reaction severity. Tryptase levels should be measured 1 to 2 hours after initiation of an allergic reaction. (c) 2021 American College of Allergy, Asthma Immunology. Published by Elsevier Inc. All rights reserved.
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