Scientific Study

BACKGROUND: Ambiguities exist regarding the diagnosis of tree-nut allergy, necessitating either elimination or performance of oral food challenges (OFC). OBJECTIVE: To examine the co-incidences 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 (SPT) 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 0.75-0.94. Knowledge of co-incident 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.