Delivered by Ingenta to: State University New York At Buffalo IP: 146.185.200.116 On: Sun, 12 Jun 2016 08:04:27 Copyright (c) Oceanside Publications, Inc. All rights reserved. For permission to copy go to https://www.oceansidepubl.com/permission.htm Egg White-Specific IgE Level as a Tolerance Marker in the Follow Up of Egg Allergy Jesus F. Crespo, M.D.,* Cristina Pascual, M.D.,* Angel Ferrer, M.D.,* A. Wesley Burks, M.D.,t J. M. Diaz Pena, M.D.,* and M. Martin Esteban, M.D.* ABSTRACT Forty patients with symptomatic immediate hypersensitiv- ity to egg who did not have atopic dermatitis were evaluated to determine if they continued to remain clinically sympto- matic. Each had specific IgE in vitro and positive prick-test to egg. All patients were on an egg elimination diet. During the follow-up an open egg rechallenge was performed along with a determination of egg white-specific IgE by CAP System. The egg white-specijic IgE values were higher in the positive challenge group than in the negative one (p < 0.01, Mann- Whitney Test). There was a direct proportional relationship between the levels of egg white-specljic IgE and the likelihood of positive challenge. Specific IgE values above 1.20 KUA/L could be adequate grounds for delaying the follow-up of egg challenge. (Allergy Proc 15:73-76, 1994) Key words: Food allergy, egg allergy, specific IgE, CAP System, follow-up. T he prevalence of food allergy is highest during the first years of life, particularly allergic reactions to egg, cow's milk, and peanut. Egg is the food most frequently implicated in immediate food allergy in chil- From the Immunoallergy Laboratory, La Paz Children's Hos- pital, Madrid (Spain)* From Pediatric Immunology Allergy, Arkansas Children's Hospital, Little Rock, Arkansast Address correspondence to Dr. J. F. Crespo. Special Immu- nology, A rkansas Children 's Hospital. 800 Marshall St .. Little Rock, AR 72202-3591 Allergy Proc. dren, both in the United States and in Europe. I . 2 In prospective studies about the natural history of allergic food reactions, it has been observed that 80-87% of confirmed symptoms disappear before the third year of life. 3 It is not known which factors determine the ap- pearance of tolerance once the patient has developed food allergy. However, it seems that both the degree of compliance with the allergen avoidance diet and the kind of allergen involved influence whether tolerance will occur. For example, patients with allergy to fish, shellfish, and nuts rarely outgrow theirhypersensitiv- ity.4On the other hand, allergy to eggsand cow's milk proteins is usually overcome in the first decade oflife. 5 Important advances have been made in the last sev- eral years regarding the knowledge of IgE-mediated food allergy. However, at this time the only effective treatment appears to be avoidance of the offending food. 4 Once an avoidance diet is established, it is diffi- cult to determine how long it should be maintained. There are not any risk markers that reliably predict patients' clinical reactivity. This can only bedetermined based on the clinical response of the patient in relation to 1)involuntary transgressions of the avoidance diet; or 2) periodic oral rechallenges with the offending food. Both could be dangerous, particularly in patients show- ing immediate hypersensitivity in whom the initial clinical reaction was severe (i.e. anaphylaxis).6 Evidence of specific IgE to the offending food is essential for the diagnosis of immediate hypersensitiv- ity. Traditionally, skin prick tests (SPT) and RAST have been the most widely used methods in the dem- onstration of food allergen-specific IgE. However, both supply only semi-quantitative information. Therefore, 73