Nut Cross-Reactivity - ACuiring Knowledge for Elimination Recommendations (NUT-CRACKER) Study

Patients will be recruited from the pool of patients referred to the investigators center for evaluation of food allergy. For each tree-nut (walnut, pecan, cashew, pistachio, hazelnut or almond) evaluated, 30 patients (ages 4-45 years old), with allergy to at least one tree-nut will be recruited from the database pool referred to above. Skin prick tests (SPT) using standardized 10 mg/ml tree-nut extracts, and BAT will be performed for all suspected allergens. Sera will be taken and sent to ThermoFisher for IgE and IgG4 binding analysis to purified components. Open OFCs will be performed for each tree-nut, unless clinically contraindicated. The results of the OFC will form the basis to determine the sensitivity and specificity of the component testing. Similarly, 40 patients with suspected sesame allergy will be administered SPT and component analysis for sesame, with correlations to OFC.

The investigators will also utilize BAT to directly test whether the identified purified components are sufficient to elicit reactivity. This objective can be met by either utilizing saved patient sera on naive basophils or directly on a subsequently obtained blood sample from the patient. For patients enrolling in OIT (secondary objective), sera will also be taken after completion of the therapeutic regimen, and IgE as well as IgG4 binding to the same components will be assessed and compared to pre-OIT results.

4.2 STATISTICAL ANALYSIS AND METHODS

4.3 Patients will be grouped by OFC their allergy status result for each tree-nut (patients with a documented IgE-mediated reaction in the previous year or a positive OFC vs. patients with regular consumption of the index food or a negative OFC). Descriptive statistics (proportions for categorical variables, means or medians and standard deviations or inter-quartile range for continuous variables) will be reported for all key participant variables, including baseline and demographic characteristics, SPT, BAT and component testing results.

For the primary objective, the sensitivity and specificity of the diagnostic tests (wheal for SPT, and CD63 induction for BAT) and IgE/IgG4 binding to the purified components in predicting OFC results allergy will be compared by receiver operating characteristic (ROC) analysis. To this end, the investigators will evaluate molecular allergens singly or in groups for their predictive utilities.