Background The demonstration of specific IgE antibodies to egg supports the existence of allergy to this food, but a correct diagnosis can only be obtained after a challenge test. Several studies have assessed different cut-off points in the level of these antibodies as predictors of clinical reactivity.
Objective Validation of the specific IgE antibodies measured by the CAP System Fluorescence enzyme immunoassay (FEIA) technique in the diagnosis of egg allergy in children under 2 years of age.
Methods A prospective study of 81 children with suspected egg allergy was performed. Specific IgE antibodies was quantified for egg white, egg yolk, ovoalbumin and ovomucoid. The diagnostic challenge test was carried out following the previously established criteria. The validity of the specific IgE antibodies was analysed using children with a negative diagnostic challenge test as control group.
Results The prevalence of egg allergy in the group studied was 79% and egg white was the allergen that showed the greatest diagnostic efficacy. The sensitivity and positive predictive value of the prick test and of the CAP to egg white were excellent and the specificity and the negative predictive value had lower values. A level of ≥ 0.35 KUA/L for specific IgE antibodies to egg white predicted the existence of reaction in 94% of the cases.
Conclusions Quantification of the specific IgE antibodies to egg white is useful in the diagnosis of egg allergy. In children under 2 years of age with a background of immediate hypersensitivity after egg ingestion and presence of specific IgE antibodies to egg white of ≥ 0.35 KUA/L, diagnostic challenge test is not necessary to establish the diagnosis of allergy to this food.