Background: Diagnosis of egg allergy based on basophil activation testing (BAT) has mainly been performed with an egg white extract or individual egg allergens rather than with clinically more representative whole-egg extracts. The impact of heating on the allergenicity of a whole-egg extract remains unassessed.
Objective: To validate BAT with gradually less heated whole-egg extracts in the diagnosis of egg allergy and as a marker of tolerance.
Methods: CD63-based BAT was performed with 5 progressively less heated extracts from cake, hard-boiled egg, omelet, soft-boiled egg, and raw egg in 10 egg-allergic (EA), 10 complete egg-tolerant (ET), and 12 non–egg-sensitized nonallergic (NEA) children. Cut-offs and diagnostic accuracy measures were established through receiver operating characteristic curve analysis. Changes in basophil response were assessed in 12 baked egg–tolerant children undergoing an 8-month gradual egg reintroduction protocol with BAT and oral food challenges prior to each reintroduction step.
Results: Basophil responses to all egg extracts were increased in EA children, but not in ET and NEA children. Responses decreased progressively with more heated egg extracts. Compared to ET children, EA children showed higher basophil sensitivity for all egg extracts. Negative BAT responses predicted clinical tolerance with 90%-100% sensitivity, 100% specificity, and a false positive rate of 2.78%. In comparison, the specificity of egg sIgE (<0.35 kUA/L) was lower (50%-78%), with a false positive rate of 40%. Basophil reactivity and sensitivity tended to decrease in baked egg–tolerant children undergoing gradual egg reintroduction, concurrent with tolerance development.
Conclusions: BAT with progressively less heated egg preparations is a sensitive and highly specific tool to discriminate EA from ET children.

Key words: Basophil, Basophil activation test, Egg allergy, Baked egg tolerance, Heated egg, Pediatric, Egg sIgE