PURPOSE OF THE STUDY.
To evaluate the usefulness of the molecular diagnostic approach in children with suspected hen’s egg (HE) allergy, the response to skin prick test by using the white boiled HE, and specific immunoglobulin E (IgE) to HE allergens (Gal d 1, Gal d 2, Gal d 3, and Gal d 5).
The study included 68 children, ranging from 1 to 11 years of age, enrolled at the Centre for Molecular Allergology in Rome, Italy. All patients were referred for suspected HE allergy.
Double blind, placebo-controlled HE challenges were performed by using boiled eggs, and if these were tolerated, challenges were performed with raw eggs. Subjects were placed in 3 groups: group A (allergic) subjects were clinically reactive to boiled egg (and were considered likely to be reactive to raw egg); group PT (partially tolerant) reacted to raw egg but tolerated boiled egg; and group ST (sensitized but tolerant) subjects were sensitized to HE but tolerated raw and boiled egg. Total and specific IgE levels for HE white and yolk were detected by using ImmunoCAP (Phadia, Sweden). Specific IgE to Gal d 1, Gal d 2, Gal d 3, and Gal d 5 were measured by using immunosolid phase allergen chip 103 microarray test (PBD, Austria), which tests 103 allergenic molecules for IgE.
Subjects were assigned as follows: group A, 19 subjects (28%); PT, 14 (20.5%); and ST, 35 (51.4%). Most (44 of 47, 94%) Gal d 1 negative patients tolerated boiled egg. Conversely, 20 of 21 Gal d 1 positive patients (95%) reacted to raw egg.
Gal d 1 negative children (specific IgE = 0 kUa/L) showed a high frequency of tolerance to boiled egg (94%), whereas Gal d 1 positive children (>0 kUa/L) showed a high frequency of raw HE allergy (95%). Therefore, Gal d 1 IgE results seem to be a useful tool to predict oral tolerance to boiled eggs.
In recent years, there has been great interest in the measurement of the response to individual allergens, rather than whole extracts, in the management of allergic diseases. This study identifies 1 such allergen, Gal d 1, as a very useful marker for identifying whether a patient may tolerate boiled egg. It should be pointed out that although Gal d 1 performance was a helpful tool, it was <90% sensitive in identifying subjects allergic to boiled egg. A negative Gal d 1 would likely not be a definitive test obviating the need for physician-supervised oral food challenge in a patient with suspected HE allergy. The test used, which is not yet Food and Drug Administration cleared, measures many different allergens, and so one must be careful to avoid diagnosing an allergy based on a sensitization that most often may not be clinically relevant.
- Copyright © 2012 by the American Academy of Pediatrics