Wheat allergy: diagnostic accuracy of skin prick and patch tests and specific IgE.Allergy 1999; 54(8):851-6A
Food allergy makes an important contribution to the pathogenesis of atopic eczema in infants. However, clinical data on cereal allergy are scanty. The objective was to study the relevance of patch testing, skin prick tests, and the concentration of wheat-specific IgE antibodies (CAP RAST) in correlation with oral wheat challenge in infants with suspected wheat allergy. In particular, we aimed to determine whether the patch test could increase the diagnostic accuracy in detecting wheat allergy.
The study material comprised 39 infants under the age of 2 years. Of these patients, 36 were suffering from atopic eczema and three had only gastrointestinal symptoms. The patients were subjected to a double-blind, placebo-controlled or open wheat challenge. Wheat-specific IgE was measured by CAP RAST, and skin prick and patch tests were performed.
Of the total 39 wheat challenges, 22 (56%) were positive. Of the positive reactions, five involved immediate-type skin reactions over a period of 2 h from the commencement of the challenge. In 17 patients, delayed-onset reactions of eczematous or gastrointestinal type appeared. Of the infants with challenge-proven wheat allergy, 20% showed elevated IgE concentrations to wheat, 23% had a positive skin prick test, and 86% had a positive patch test for wheat. The specificities of CAP RAST, skin prick tests, and patch tests were 0.93, 1.00, and 0.35, respectively.
Our study demonstrated that patch testing with cereals will significantly increase the probability of early detection of cereal allergy in infants with atopic eczema and is helpful in the planning of successful elimination diets before challenge. The specificity of the patch test was lower than that of other tests. Therefore, confirmation of the diagnosis with the elimination-challenge test is essential in patients with positive patch test results.