Predicting Outcomes of Baked Egg and Baked Milk Oral Food Challenges Using a Ratio of Food-Specific IgE to Total IgE

Abstract

Food-specific IgE (sIgE) and skin prick tests are used to risk-stratify patients for oral food challenges (OFCs). More accurate predictors are needed. Our objective was to evaluate the ratio of sIgE to total IgE (tIgE) (the “Ratio”) as a predictor of outcomes for OFCs to baked egg and baked milk and to determine if the Ratio better predicts the outcome of OFCs compared with sIgE alone. Data from all OFCs to baked (extensively-heated) egg and baked milk from January 2010 until January 2016 were reviewed for pre-challenge sIgE and tIgE, post-challenge outcome, and severity of reaction in failed challenges. The Ratio was calculated for egg white, ovomucoid, and milk and assessed as a predictor of OFC outcome with receiver operator characteristic (ROC) curves. The pre-challenge Ratios of egg white and milk were significantly higher in failed challenges as compared to passed challenges, 1.19% vs. 0.71% (p=0.02) for baked egg, and 3.68% vs. 0.75% (p=0.02) for baked milk. The Ratio for ovomucoid was not significantly higher in failed as compared to passed challenges for baked egg, 0.50% vs. 0.44%, (p=0.47). When assessing ROC curves, the Ratio did not perform significantly better than sIgE alone in predicting challenge outcome for egg white, 0.62 vs 0.68 (p=0.24), ovomucoid 0.54 vs. 0.58 (p=0.55), or milk 0.73 vs 0.69 (p=0.70). The Ratios for egg white and milk were predictive of outcomes of baked egg and baked milk challenges, respectively; however, the Ratio was not more predictive than sIgE alone.