Pediatric Allergy

Effectiveness of a Cutoff Allergy Test Result to Guide Performance of Baked Egg Challenge Tests in Children with Egg Allergy

Egg allergy is among the more common food allergies in children and can result in significant dietary restrictions. Fortunately, most children with egg allergy eventually tolerate the food as they grow older. Prior to ultimate tolerance of straight eggs, many children will first develop tolerance to baked goods where egg is a listed ingredient. This provides expanded dietary options for these children, and theoretically regular consumption of this type of baked egg may accelerate ultimate tolerance of straight eggs. Food challenge testing currently represents the standard of care for assessment of food allergy status, aided by history, physical exam, percutaneous and serum allergy tests. Correlation studies comparing straight milk challenge results with serum milk-specific IgE (Immunocap method) concentrations, predict an approximate 95% likelihood for a clinical allergic reaction if an older child has an Immunocap result of >14 Ku/L, or if a child under 2 year has a result of >5 Ku/L. These represent suggestive cutoff results, above which challenge testing is not recommended without a history of recent tolerance of an accidental exposure. Similar correlative data for baked egg challenges is not as strong, and an Immunocap result as high as 20 Ku/L has been suggested as the recommended cutoff value. We propose to review our baked egg challenge experience over the four years 2015-2018 to determine the reaction rates at various Immunocap values, in order to give parents and Allergists information to help in their decision-making, and to determine if another cutoff Immunocap value is safer and more appropriate.

Baked Egg Challenge Reactions (N = 101)

2015 - 2018

Baked Egg Reaction Relative to Basleine lgE Titers (N = 101)

2015 - 2018

If we stratify based on an Immunocap value of 4.0 Ku/L, the recommended cutoff from last year’s project, then below 4.0, 58 total challenges had 8 reactions, for a reaction rate of 13.8%. Above 4.0 Ku/L, 43 total challenges had 24 reactions, for a reaction rate of 55.8%. Given this difference, 4.0 Ku/L still seems to represent a valid cutoff value. In general, this is a safe procedure, with only 7/101 challenges having reactions needing Epi, and the Immunocap results for these seven were at 1.05 Ku/L, 6.31 Ku/L, 7.39 Ku/L, 7.76 Ku/L, 18.80 Ku/L, 40.50 Ku/L, and 80.80 Ku/L. As with last year, there was no age correlation with the reaction rates.

This reaction rate for 2018 is lower than that for the previous three years, at 20%, compared to a combined reaction rate for 2015-17 of 35.5%. I would like to think this was due to a behavior change of Allergists and parents in selection of candidates for baked egg challenge based on our previous data suggesting a high success rate for challenges in children with Immunocap titers 4.0 Ku/L or less, and a high reaction rate in children with Immunocap titers above 4.0 Ku/L. However, 11/25, or 44% of 2018 baked egg challenge tests were performed in children with Immunocap titers above 4.0 Ku/L, compared with 46.2% performed on children who had Immunocap titers above 4.0 Ku/L in 2017. This implies that the information presented last year had little impact on the behavior of Allergists and parents in selecting egg-allergic children for baked egg challenge tests, and that other factors resulted in the lower reaction rate in 2018.

Based on these results, I recommend to the QI/Safety team that we will continue to inform parents and remind our Allergy staff regarding these reaction rates for baked egg challenges, namely that there is a 55.8% reaction rate above 4.0 Ku/L, and a 13.8% reaction rate below 4.0 Ku/L. Most will likely wait to perform such a challenge test until their child’s egg Immunocap result drops below 4.0 Ku/L, unless the child in question has had tolerance of an accidental baked egg exposure, or if the potential benefits outweigh the risks of challenge.