Detection of IgE antibody to a radiocontrast medium

Very little is known about the mechanisms underlying adverse reactions to radiocontrast medium. On the basis of the clinical features of the adverse reactions, it has generally been considered that an IgE-dependent mechanism is not involved in these adverse reactions, and only a few studies have demonstrated the presence of IgE antibody to radiocontrast medium in patient sera.

We assayed for IgE antibody to ioxaglic acid (Hexabrix), a representative radiocontrast medium, in the sera of patients who had developed adverse reactions to ioxaglic acid. A conjugate was prepared by coupling succinyl ioxaglic acid to human serum albumin. Enzyme immunoassay and radioimmunoassay for the detection of IgE antibody to ioxaglic acid in patient sera were constructed by physical adsorption or by covalent coupling of the conjugate on solid supports.

When the radioactivity or the absorbance exceeding the mean plus 3 SD for normal healthy subjects was regarded as positive, IgE antibody was detected in the sera of 47.1% of the patients who had a past history of adverse reactions to ioxaglic acid and 16.2% of those who had experienced adverse reactions to ioxaglic acid within 24 h before the blood collection, although the IgE antibody levels were low. On the other hand, IgE antibody to ioxaglic acid was not detected in the sera of patients with no history of adverse reactions to ioxaglic acid. Inhibition experiments revealed the presence of IgE antibody specific to ioxaglic acid in the serum defined as positive for IgE antibody to ioxaglic acid. The presence of IgE antibody to ioxaglic acid did not always correlate with the activation of mast cells due to the occurrence of adverse reactions to ioxaglic acid.

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 of IgE antibody in the serum of at least some patients.