Baked egg food challenges - clinical utility of skin test to baked egg and ovomucoid in children with egg allergy

Abstract

Background: Many children with IgE-mediated egg allergy can tolerate products containing extensively heated (baked) egg. Aside from food challenge, there are no tests which reliably predict tolerance to baked egg in egg-allergic individuals.

Objectives: To determine if skin prick test (SPT) to baked egg (muffin) and ovomucoid can predict the outcome of baked egg challenges in egg allergic patients.

Methods: In this prospective study, children with a recent history of immediate allergic reactions to egg [and corroborative positive SPT or serum-specific IgE (ssIgE) to egg] or those with SPT/ssIgE > 95% PPV for egg allergy were invited to undergo an open standardized baked egg (muffin) challenge. SPT to egg white, ovomucoid, and fresh muffin were performed immediately prior to challenge.

Results: One hundred and forty-three egg allergic children underwent baked egg challenge and of these, 90 (63%) tolerated 1 g of egg protein in a baked muffin. Of the 53 positive challenges, eight (15%) had respiratory and/or cardiovascular symptoms. The median SPT diameters in positive challenges compared with negative challenges were baked muffin - 6.0 mm/4.0 mm and ovomucoid 7.5 mm/5.0 mm respectively. Receiver operating characteristic (ROC) curves were generated for SPT to baked egg and ovomucoid. The area under the curve was 0.68 for baked egg, and 0.67 for ovomucoid. A muffin SPT of < 2 mm had a negative predictive value of 88% and an ovomucoid SPT ≥ 11 mm had a positive predictive value of 100%.

Conclusions and clinical relevance: A SPT of < 2 mm to muffin had a high negative predictive value to baked egg challenge. Ovomucoid SPT ≥ 11 mm was very likely to predict a reaction to baked egg. In these children, deferring the challenge would be appropriate.

Keywords: baked egg; egg allergy; food challenge; ovomucoid.