Evaluation of IgE serum level by radial immunodiffusion and radioimmunoassay in allergic diseases.

Sensitive radioactive methods are usually required for assay of low or normal serum levels of IgE up to 1.000 I.U./ml. However radioimmunoassay or other radioactive techniques are not always available or practical in routine diagnosis of allergic patients. Therefore, some modifications of the conventional radial immunodiffusion techniques have been tried for IgE. We have studied the comparative results of radioimmunoassay (RIST) and a modified radial immunodiffusion for IgE evaluation in allergic diseases. In 18 subjects a solid phase radio-immunoassay for IgE has been done. In 14 no allergic subjects total IgE serum level determined by the RIST method was 248 +/- 210 (I.U./ml--m +/- 2SD). A double precipitation or a intensification method of immunodiffusion employing Partigen plates (Behring-Werke) has been applied for global IgE assay in routine laboratory work in the last months. Serum IgE levels were studied by this method in 20 normal subjects and 206 patients referred for diagnosis of allergic disease. A modification of the double precipitation technique allowed us to measure IgE levels above 260 I.U. In normal subjects IgE serum level was 355 +/- 182 I.U. (M +/- 2SD). In 120 extrinsic asthmas the range was 9.580--260 I.U. and mean value 2.120 +/- 627 I.I. and the range 1.760--300 I.U. 14 cases of pollinosis were studied during the grass pollen season. Mean values were 1.840 +/- 1.270 I.U. and range 2.760--600 I.U. 18 cases of perennial allergic rhinitis the mean value was 1.868 +/- 1.301 I.U. and the range 2.600--260 I.U. In 12 urticarias the mean value was 1.730 +/- 1.252 I.U. and the range 2.300--260 I.U. Highest IgE serum levels occurred in atopic asthmatics with mite sensitivity. A general positive relationship was observed between the intensity of skin reactivity and elevated serum IgE level. However some exceptions to this rule have been observed. A simultaneous assay of serum immunoglobulins IgG, IgA and IgM by radial immunodiffusion has been done in some subjects. No correlation has been found between serum level of IgE and serum concentrations of IgG, IgA or IgM. The use of a modified immunoradial diffusion technique can therefore be a useful diagnostic tool in the study of allergic diseases. The results obtained confirm that serum IgE level is increased in most of the cases of type I allergic reactions but also in some patients presenting intrinsic asthma.