NUT Co Reactivity - ACquiring Knowledge for Elimination Recommendations (NUT CRACKER) study.

BACKGROUND: Ambiguities exist regarding the diagnosis of tree-nut allergy, necessitating either their elimination or the performance of oral food challenges (OFCs). OBJECTIVE: To examine the coincidences of allergies among tree-nuts and improve diagnostic testing to minimize the need for OFC. METHODS: Eighty-three patients prospectively evaluated for walnut, pecan, cashew, pistachio, hazelnut, and almond allergy. A history of previous reactions was obtained, and standardized skin prick tests (SPTs) using finely ground tree-nut solution and basophil activation tests (BAT) were performed. Patients underwent OFC for each tree-nut they eliminated and to which a reaction in the previous 2 years was not documented. RESULTS: While most patients were sensitized to 5-6 tree-nuts, over 50% were allergic to only 1-2 tree-nuts. The highest rate of allergy in sensitized patients was observed for walnut (74.6%) and cashew (65.6%). The rate of co-allergy for most tree-nuts was <30%. Two-thirds of walnut- and cashew-allergic patients were also allergic to pecan and pistachio, respectively, while all pecan- and pistachio-allergic patients were allergic to walnut and cashew, respectively. Receiver-operating characteristic analysis for SPT and BAT was tree-nut dependent and yielded area under the curve (AUC) values ranging from 0.75 to 0.94. Knowledge of coincident allergies in these pairs along with the combination of SPT and BAT correctly distinguished allergic from tolerant patients for walnut (87%), pecan (66%), cashew (71%), and pistachio (79%). CONCLUSION: The data presented here should assist in differentiating between allergic and tolerant patients, decrease the need for OFC, and allow for appropriate elimination recommendations.