The diagnostic performance of allergy tests is impacted by the immunomodulatory effects of egg consumption, according to recent findings, with the basophil activation test (BAT) being the most reliable assessment among those consuming eggs.¹

These findings were the results of the ‘BAT2’ study assessing and stratifying the diagnostic results of various assessments based on egg consumption status. The research was led by Andreina Marques-Mejias, MD, PhD, from the School of Life Course Sciences’ department of women and children’s health at King’s College London in the United Kingdom.

Prior research had linked levels of allergen-specific immunoglobulin E (IgE) and basophil activation with egg allergy phenotypes, the investigators noted.² Despite this fact, there is currently not an objective marker which can reliably indicate the point at which patients who are egg-allergic may be able to tolerate baked egg.

“Herein, we report the egg consumption status in a cohort of children being assessed for egg allergy and its influence in the diagnostic performance of allergy tests to predict the outcome of (double-blind placebo-controlled food challenges) to (baked egg),” Marques-Mejias and colleagues wrote.

Background and Findings

The investigators conducted the BAT 2 study, beginning with the prospective recruitment of children who were suspected of IgE-mediated allergy to sesame, egg, cow’s milk, or cashew nuts. They specifically looked into children under evaluation for potential egg allergies and implemented double-blind placebo-controlled food challenges.

These challenges were done first with baked egg, and upon passing this, with loosely cooked egg. When the oral food challenge took place, the parents of these participants filled out a food-frequency questionnaire, followed then by skin prick tests, blood collection for serology, and the basophil activation testing for the children.

The families were given questionnaires to report on their child's frequency of egg intake and to approximate the overall amounts of different egg forms consumed, in relation to a typical age-appropriate portion for a child. These questionnaires were carried out at various study time points, including every 2 months for a total of 2 years following the conclusion.

Children with any type of egg ingestion were classified by the investigators as ‘consumers,’ and those who were shown to have kept away from all forms of egg at the point of research entry were labeled by the research team as ‘avoiders.’

The skin prick tests were carried out to assess participants’ IgE sensitization to various types of egg preparations. The investigators’ research, overall, was conducted to compare the overall utility of skin prick tests to egg extract, raw egg, and baked egg in the diagnosing of baked egg and loosely-cooked egg allergies.

The basophil activation test involved basophils being stimulated through the use of various substances. Participants’ total IgE, sIgE, and IgG4 to specific egg elements were assessed by the investigators.

By the outset of the research, the investigators reported that 45% of the subjects were shown to have been egg consumers, and 55% to have been strictly avoiders. Those labeled in the work as avoiders were shown by the team to have higher allergic markers and lower sIgG4 levels compared to those of participants labeled as consumers.

The basophil activation test, among consumers, was shown to have had the most accurate diagnostic performance (area under the curve [AUC] = .912), followed by SPT to raw egg (AUC = 0.805). Next in the list, in order of effectiveness were EW-sIgE (AUC = 0.738) and then OVA-sIgE (AUC = 0.732).

The investigators found that among those who were avoiders, baseophil and EW-sIgE tests were shown to be the most useful (AUC = 0.834 and 0.833, respectively). Through the use of 100% sensitivity and specificity cut-offs, the team noted that consumers needed oral food challenges for 33% with the basophil test, 53% with skin prick test, 61% with OVA-sIgE, and 73% with EW-sIgE.

Among those labeled avoiders, the investigators showed that the percentages were 73% with baseophil, 79% with EW-sIgE, and 93% with skin prick test to egg whites.

“Overall, our study supports the incorporation of BAT in the diagnostic workup of (baked egg) allergy to reduce the number of (oral food challenges) and improve diagnostic accuracy when assessing whether egg-allergic children can tolerate (baked egg),” they wrote.

References

1. ^{Partial Egg Consumption Modifies the Diagnostic Performance of Allergy Tests to Predict Outcome of Double-Blind Placebo-Controlled Food Challenges to Egg. The Journal of Allergy and Clinical Immunology. December 26, 2023. https://doi.org/10.1016/j.jaip.2023.12.036. Date accessed: January 23, 2024.}
2. ^{Berin MC, Grishin A, Masilamani M, et al. Egg-specific IgE and basophil activation but not egg-specific T-cell counts correlate with phenotypes of clinical egg allergy. J Allergy Clin Immunol. 2018; 142: 149-158.e8.}