Correlation Between Specific Immunoglobulin E Levels and the Severity of Reactions in Egg Allergic Patients
Authors: Pesek Robbie D. , Perry Tamara T. 
Published: October 2008

Benhamou AH, Zamora SA, Eigenmann PA. Pediatr Allergy Immunol. 2008;19(2):173–179

PURPOSE OF THE STUDY. To determine if specific immunoglobulin E (IgE) antibody titers to egg were predictive of the severity of reaction during a standardized food challenge.

STUDY POPULATION. The study was a retrospective review of children who underwent oral food challenges to egg over a 2-year period. Median age of patients was 3.9 years (range: 16 months to 11.9 years). Children with high egg-specific IgE titers and those with a severe reaction &lt;2 years earlier were not tested.

METHODS. Children with immediate-type reactions were tested by open food challenge, and those with atopic dermatitis or equivocal reactions were tested by double-blind, placebo-controlled food challenge. Graded challenges were performed with pasteurized raw egg, cooked egg, or egg hidden in a chocolate testing preparation. The challenge was terminated when the patient reached a total dose of 45 g of egg or if there was unambiguous clinical reactivity and reaction severity was graded.

RESULTS. Of the 51 challenges performed during the study period, 35 (69%) were positive. Thirteen (37%) of the positive challenges were considered severe. An egg radioallergosorbent (RAST) assay result of ≥17.4 kU/L was associated with 95% probability of having a positive challenge; 8.2 kU/L was associated with a 90% probability. For all challenges, egg-specific IgE titers ranged from &lt;0.35 to 14.9 kU/L. The negative challenge group had a median egg-specific IgE titer of 1.17 kU/L (range: 0.35–6.41 kU/L); the mild-to-moderate group median was 2.47 kU/L (range: 0.35–14.9 kU/L); and the severe group median was 3.70 kU/L (range: 1.18–11 kU/L). The differences of median egg-specific IgE levels were statistically significant (P = .006). Children with a positive challenge who received cooked egg were found to have a higher specific IgE level versus those who received raw egg (P = .016), but there was no statistically significant difference between severity of reactions between these groups. The median dose that caused a mild-to-moderate reaction was 6 g (range: 2.5–20 g) and was the same median dose that caused severe reactions (range: 0.5–15 g).

CONCLUSIONS. There is a correlation between median egg-specific IgE levels and the severity of reaction during oral food challenge to egg. These levels may be helpful in predicting a potential reaction to egg.

REVIEWER COMMENTS. It is often assumed that reaction severity correlates with the food-specific IgE level, but most studies have refuted this notion. Here, a relationship was determined. However, it is difficult to assess the clinical utility of these results, because there was considerable overlap of the ranges of egg-specific IgE levels between groups. These findings may be more relevant to the controlled setting of a diagnostic food challenge rather than to the community setting in which a large or uncontrolled dose of egg might be ingested. In a real-life setting, a severe reaction may occur even with a low egg-specific IgE level, particularly if one considers patient-dependent factors such as concurrent diagnosis of asthma or personal history of a previous severe reaction.