Are quantitative results of serum specific IgE assays clinically meaningful?

In vitro allergy testing is based mainly on the measurement of so-called specific IgEs in serum, commonly referred to as RASTs. Their results are expressed both in semi-quantitative and quantitative units, i.e. classes and kU/l, respectively. Does this double system obscure and therefore limit the clinical utility of quantitative RAST results? Are the results of these blood tests sufficient to establish a diagnosis of allergy or to predict the development of a future allergy in a given patient? And, in this respect, can population-based risk curves, as recently suggested, improve the efficiency of in vitro allergy testing? This article discusses these questions on theoretical grounds as well as on a review of experimental data. It is concluded that quantitative RAST results must not be interpreted independently of clinical information because they do not correlate with the patient's clinical reactions and therefore must be interpreted together with the rest of the patient's record. Risk curves are not the answer because they add another problem to the limitation of quantitative RAST results, i.e., they are strongly dependent on the characteristics of the population from which they were derived (e.g., age, allergic environment, etc.). Therefore, these curves are of limited value for a given patient seen in daily practice. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.