Relationship between food-specific IgE concentrations and
the risk of positive food challenges in children and adolescents
Sampson HA, Ho DG. J Allergy Clin Immunol. 1997 Oct;100(4):444-51.
Abstract
BACKGROUND: The double-blind, placebo-controlled food
challenge (DBPCFC) is the "gold standard" for diagnosis
of food hypersensitivity. Skin prick tests and RASTs are sensitive
indicators of food-specific IgE antibodies but poor predictors
of clinical reactivity. Previous studies suggested that high
concentrations of food-specific IgE antibody were predictive
of food-induced clinical symptoms. Because the Pharmacia CAP System
FEIA (Pharmacia Diagnostics AB, Uppsala, Sweden) provides
a quantitative assessment of allergen-specific IgE antibody,
this study was undertaken to determine the potential utility
of the Pharmacia CAP System FEIA in diagnosis of IgE-mediated food
hypersensitivity.
METHODS: Sera from 196 patients with food
allergy were analyzed for specific IgE antibodies to egg,
milk, peanut, soy, wheat, and fish by the Pharmacia CAP System
FEIA. Sera were randomly selected from 300 stored samples of
children and adolescents who had been evaluated by history,
skin prick tests, and DBPCFCs. The study population was highly
atopic; all patients had atopic dermatitis, and approximately
50% had asthma and allergic rhinitis at the time of initial
evaluation. The performance characteristics of the Pharmacia
CAP System FEIA were compared with those of skin prick tests
and the outcome of DBPCFCs or "convincing" histories
of anaphylactic reactions
RESULTS: The prevalence of
specific food allergies in the study population varied from
22% for wheat to 73% for egg. Allergy to egg, milk, peanut,
and soy accounted for 87% of confirmed reactions. The performance
characteristics of skin prick tests and the Pharmacia CAP System
FEIA (egg, milk, peanut, fish) were comparable, with excellent
sensitivity and negative predictive accuracy but poor specificity
and positive predictive accuracy. The performance characteristics
of the Pharmacia CAP System FEIA for soy and wheat were poor.
For egg, milk, peanut, and fish allergy, diagnostic levels
of IgE, which could predict clinical reactivity in this population
with greater than 95% certainty, were identified: egg, 6
kilounits of allergen-specific IgE per liter (kUA/L);
milk, 32 kUA/L; peanut,
15 kUA/L;
and fish, 20 kUA/L.
CONCLUSIONS: When compared
with the outcome of DBPCFCs, results of the Pharmacia CAP System
FEIA are generally comparable to those of skin prick tests
in predicting symptomatic food hypersensitivity. Furthermore,
by measuring the concentrations of food-specific IgE antibodies
with the Pharmacia CAP System FEIA, it is possible to identify
a subset of patients who are highly likely (>95%) to experience
clinical reactions to egg, milk, peanut, or fish. This could
eliminate the need to perform DBPCFCs in a significant number
of patients suspected of having IgE-mediated food allergy.
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