Detection of IgE antibody to a radiocontrast medium

Background Very little is known about the mechanisms underlying adverse rea ctions to radiocontrast medium. On the basis of the clinical features of th e adverse reactions, it has generally been considered that an IgE-dependent mechanism is not involved in these adverse reactions, and only a few studi es have demonstrated the presence of IgE antibody to radiocontrast medium i n patient sera. Methods We assayed for IgE antibody to ioxaglic acid (Hexabrix(R)), a repre sentative radiocontrast medium, in the sera of patients who had developed a dverse reactions to ioxaglic acid. A conjugate was prepared by coupling suc cinyl ioxaglic acid to human serum albumin. Enzyme immunoassay and radioimm unoassay for the detection of IgE antibody to ioxaglic acid in patient sera were constructed by physical adsorption or by covalent coupling of the con jugate on solid supports. Results When the radioactivity or the absorbance exceeding the mean plus 3 SD for normal healthy subjects was regarded as positive, IgE antibody was d etected in the sera of 47.1% of the patients who had a past history of adve rse reactions to ioxaglic acid and 16.2% of those who had experienced adver se reactions to ioxaglic acid within 24 h before the blood collection, alth ough the IgE antibody levels were low On the other hand, IgE antibody to io xaglic acid was not detected in the sera of patients with no history of adv erse reactions to ioxaglic acid. Inhibition experiments revealed the presen ce of IgE antibody specific to ioxaglic acid in the serum defined as positi ve for IgE antibody to ioxaglic acid. The presence of IgE antibody to ioxag lic acid did not always correlate with the activation of mast cells due to the occurrence of adverse reactions to ioxaglic acid. Conclusions A small amount of IgE antibody to ioxaglic acid was detected in the sera of some patients with a history of adverse reactions to ioxaglic acid, and these adverse reactions may be partly explained by the presence o f IgE antibody in the serum of at least some patients.