In vitro diagnosis of atopic allergy The occurrence and clustering of positive RAST results as a function of age and total IgE concentration

Abstract

Specific IgE antibodies were determined on a routine basis in patient sera using the radioallergosorbent test (RAST) with a panel of ten common allergens. Total IgE was also assayed. Of all positive RAST reactions observed, 74% were against the following allergens: horse and cat epithelium, birch and timothy pollen, and house dust. Clustering (occurrence together with significantly elevated frequencies) accompanied both positive reactions to some animal danders and food allergens. Children in all age groups had significantly more positive food RAST results than adults, and this explains the clustering among food allergen results. Children aged 0-4 years had few positive pollen results. Among those with at least one positive RAST result, the mean number of positive results was 3.3, a figure which did not vary with age. In the present patient population 37% had a total IgE above the upper reference (normal) limit, and of these 95% had at least one positive RAST result. A normal or low IgE value was found to be less informative.