Comparative evaluation of the multiple RAST and discrete RAST for inhalant allergy.

With the conventional, discrete RAST various tests are required to detect IgE of different specificities in the same serum. To overcome this problem and to reduce the costs, a multiple RAST with seven different mixtures was compared with the individual mixture constituents and with the 12 individual allergens currently in use in our department. One grass pollen mixture (gx3), two weed pollen mixtures (wx3, wx4), two tree pollen mixtures (tx5, tx6), one mould mixture (mx1) and one epithelial mixture (ex1) were used. A mixture of mites was not evaluated as there is only one important pathogenic organism in our regions (Dermatophagoides pteronyssinus or House dust mite). For grasses the gx3 mixture offered no advantage over the discrete RAST. The weed mixture wx3 was more sensitive than the most common discrete RAST's but at the cost of specificity. The wx4 mixture should not be used because the specificity is too low. The tree mixtures were not significantly more sensitive than the most common individual tree allergens, and were less specific. Mould mixtures should not be used because there is little cross-reactivity between the individual allergens, thus using a mixture would necessitate the subsequent determination of individual allergens, and the number of tests and the cost would be even higher. Neither should a mixture be used for epithelia because one wants to detect allergies to individual allergens. Moreover, the sensitivity of the epithelial mixture was too low. In general, we suggest the use of a limited panel of discrete RAST's instead of mixtures.