The Utility of BAT in Diagnosing Treenut Allergy
Monday, March 6, 2017: 2:45 PM
Thomas B. Murphy Ballroom 3-4 (Georgia World Congress Center, Building B)
Michael R Goldberg, MD,PhD, , , , ,
Rationale:   Patients with known allergy to a single tree-nut are often sensitized to other tree-nuts, requiring an oral food challenge (OFC) for definitive diagnosis. Since OFCs are time-consuming and not without risk, we evaluated the utility of the basophil activation test (BAT) to diagnose true clinical allergy.

Methods: Patients with a history of reaction to tree nuts (walnut, hazelnut, cashew, pistachio, almond, and pecan) were evaluated.  OFCs were performed to confirm clinical reactivity for all nuts except if they were being currently consumed or clinically contraindicated based on a recent severe reaction.  Induced basophil CD63 expression was determined and evaluated against the patients' clinical allergic status for each nut, respectively.

Results: The allergic status of patients was determined (walnut:23/30 [77%], hazelnut: 7/28 [25%], cashew: 12/28 [43%], pistachio: 6/27 [22%], pecan: 13/28 [46%]). No patients were found allergic to almond (0/29). The performance of BAT for allergy diagnosis was evaluated  by Receiver operating characteristic (ROC) curve analysis, yielding an area under the curve (AUC) ± SE of 0.96±0.035, 0.87±0.067, 0.99±0.014, 0.91±0.059, 0.93±0.060 for walnut, hazelnut, cashew, pistachio, and pecan, respectively.  Using a critical test value of  5% CD63 induction, we obtained paired sensitivities and specificities of 96%, 86% (walnut);  86%,76% (hazelnut);  83%,100% (cashew); 100%, 86% (pistachio);  85%, 100% (pecan). False positive BAT (>5% CD63) were observed for 3/14 (21%) of patients with zero or one nut allergies, and 6/16 (38%) patients with multiple nut allergies.

Conclusions:   Depending on the nut tested, BAT may obviate the need for OFC to diagnose or rule out treenut allergy.