Comparison of ultrasensitive methods for the measurement of IgE

Because the study of human IgE synthesis and regulation requires exquisitely sensitive and rapidly performed methods for assay of in vitro IgE production, we compared 4 methods for radiometric immunoassay (RIA) of human IgE: double antibody RIA (DARIA), ultrasensitive enzymatic RIA (USERIA), sensitive paper radioimmunosorbent test (SPRIST) and microtiter solid-phase RIA (MSPRIA). IgE protein was measured in serum samples and cord bloods. The USERIA and the MSPRIA consistently detected levels of IgE as low as 27-35 pg/ml. The DARIA and SPRIST were less sensitive. Comparison of the USERIA and the MSPRIA favored the latter because: (1) it is a more rapidly performed assay, (2) it involves fewer manipulations, and (3) it has less variability. We conclude that the MSPRIA for IgE is superior to the other methods both as a research tool for measuring minute quantities of IgE protein (as in tissue culture supernatants) and for measuring IgE in serum samples where concentrations fall below 1 ng/ml (0.42 IU/ml; 1 IU = 2.4 ng).