Using BAT As a Predictor for Baked Egg Oral Food Challenge Outcomes
Sunday, March 6, 2016
South Exhibit Hall H (Convention Center)
Opal Kamdar, MD, Maaria Syed, MD, Kristin A Erickson, Ashleigh A. Olson, MD, Christine Szychlinski, Miao Cai, MS, Anne Marie Singh
Rationale: Egg-allergic children are often able to tolerate extensively heated egg products. Although sIgE to ovomucoid has been suggested, tests to predict which patients will safely pass an oral food challenge (OFC) to baked egg are not well described. 

Methods:  A retrospective chart review of 24 OFCs to baked egg and the most recent ovamucoid sIgE were examined to determine cut-off values for sIgE to predict a positive OFC outcome. Basophil activation tests (BAT) were conducted with egg white, ova, and ovamucoid antigens of non-egg allergic (n=22) and egg allergic (n=16) patients. Basophil activation was measured by CD63 expression. A stimulation index (SI) for BAT was calculated as a ratio between basophil degranulation in response to allergen and basophil degranulation in response to negative control. Receiver operative curves were created for BAT results. Severity of reaction for each patient was established using a standardized scoring system and a linear regression model was used to examine its correlation with BAT results.

Results:  Ovamucoid sIgE demonstrated poor accuracy in predicting OFC outcomes to baked egg allergy with a sensitivity of 67%, false positive rate of 29% and AUC ROC=.690. Stimulation Index of BAT to ovalbumin showed a sensitivity of 87.5%, false positive rate of 16%, AUC ROC=.875, with an optimal cut-off of 13.8. BAT results did not correlate with severity of reaction in the small sample size of patients analyzed.

Conclusions:  BAT may be a reliable tool for predicting an oral food challenge outcome to baked egg in egg allergic children.