[Relation between the total plasma IgE concentration and the prevalence of the various RAST (radioallergosorbent) classes of allergy].

The aim of this study was to analyze the prevalence of every RAST (Radio-Allergo-Sorbent-Test) class in terms of total IgE serum level, and to establish the existing relationship between the total IgE level and the probability to obtain a definite specific IgE concentration. The analyzed sample was 352 total IgE values obtained by means of RIA in 611 patients of both sexes and ages from 5 to 15 years [corrected], and the RAST results of every one of them. As mathematical model, Logit was used. It was established a mathematical function [p = 1/(1 + K(-1).IgE-beta)], which allows to calculate the probability to obtain a definite RAST class of allergy for a definite total IgE level. The propounded model establishes that, for a plasmatic IgE level lower or equal to 17.0 kU/l (11.5-23.3), the probability to obtain a specific IgE concentration lower than 0.35 kU/l (absence of allergy) is 0.95. For a total IgE level of 23.32 kU/l (16.43-30.91) there is a probability of 0.95 that RAST result to be negative or slightly positive. Finally, for a total IgE level of 62.6 kU/l (49.20-76.55) specific IgE levels of classes 0 or 1 or 2 would be obtained. The mathematical model allows to predict the most probably RAST class of allergy result once known the total IgE level. It makes easier the allergological diagnostic and facilitates, in some cases, to omit the RAST, with the resulting saving of time and money.