Comparison of serum IgE determination by conventional radioimmunoassay (RIST) and by a modified (sandwich) technique (PRIST).

It has been reported that the sandwich technique (PRIST) is a more accurate method for determining serum IgE levels than the conventional radioimmunoassay (RIST), especially for low IgE levels. By using half the volumes prescribed for RIST and by introducing a 3-h preincubation step at room temperature, IgE values in the range of 30-4000 I.U./ml could accurately be established. It is concluded that the proposed modification may replace the conventional RIST for routine purposes, because it offers comparable accuracy, is more exonomical, and provides better results in the low IgE range. Discordant results between RIST and PRIST cannot be correctly interpreted, because interfering serum factors may cause either exaggerated IgE values with RIST, or falsely low values with PRIST.