RAST-based allergen assay methods.

The RAST principle has been utilized for the detection and assay of allergens of various origins. RAST-based methods have the advantage of being convenient, accurate and specific by making use of the IgE antibodies, considered as mediators of the atopic allergic reactions, as reagents in vitro. Two improved assay procedures, a direct titration and an inhibition method, have been used for the estimation of extract potencies and for the assay of separate allergens. The specificity of the assays is determined by the specificity of the IgE (sera from allergic patients) used as the main reagent. Specific assay of separate components in heterogeneous extracts may be achieved in some cases by careful characterization of the sera or by selective blocking of irrelevant IgE. The potency of allergen concentration may be calculated and expressed in arbitrary units, and the accuracy and sensitivity of the two methods are similar. The coefficient of variation is in the range 10 to 25% provided that standardized reagents are used. Sensitivity of the assays is about 200 ng per ml. The lower limit for detection of allergen is 10-100 times lower.