Allergic Immediate Hypersensitivity to Iodinated Contrast Media

Background: Immediate hypersensitivity reactions (IHR) to iodinated contrast media (ICM) have traditionally been considered nonallergic; however, the increasingly frequent reporting of positive skin test and basophil activation test results suggests a specifi c allergic mechanism in some patients. Skin tests have been proposed as a useful tool for diagnosis, although their sensitivity and predictive values remain to be determined. The role of controlled challenge testing has not been assessed. Objective: We aimed to evaluate the role of controlled challenge testing in skin test–positive IHR to ICM. Patients and Methods: We evaluated 106 patients with IHR to ICM by performing skin tests with the agent that caused the reaction. Patients with a positive result were selected. Skin tests were extended to a series of 8 ICMs; 5 patients underwent controlled challenge test with an alternative skin test–negative ICM; a further 2 patients underwent computed tomography with an alternative skin test–negative ICM. No premedication was administered. Results: Intradermal test results were positive to the ICM that caused the reaction in 11 out of 106 patients (10.4%). Five of the 11 patients tolerated a controlled challenge test with an alternative skin test–negative ICM. The 2 patients who underwent computed tomography with an alternative skin test–negative ICM tolerated the medium. Conclusions: Skin tests are useful for the diagnostic workup in patients with an allergic IHR to ICM. Since ICM cannot be avoided in many patients because they are irreplaceable in some diagnostic or therapeutic techniques, an alternative safe ICM should be investigated for future procedures. We propose the use of controlled challenge tests based on skin test results to address this need in skin test–positive reactions in order to identify an alternative non–cross-reactive ICM.