Objective assessment of immediate iodine-based contrast media hypersensitivity reactions using skin and drug provocation testing

Background With increasing importance of iodine-based contrast media (ICM) in radiology, a label of allergy to ICM has significant impact on patient management, and objective testing for ICM allergy can help guide subsequent administration.Purpose To correlate skin testing with drug provocation test (DPT) outcomes and determine cross-reactivity between our institution's three available ICMs.Material and Methods Eligible patients who presented to our institution's radiology department within a 3-year period with suspected ICM allergy were referred to the allergist for evaluation with skin testing +/- DPT. Patients who tested negative were followed up to evaluate for any reaction after ICM re-exposure in subsequent contrast-enhanced computed tomography scans.Results A total of 72 cases underwent testing. Concordance between skin testing and DPT was 85.7% (6/7) for iohexol, 65.1% (28/43) for iodixanol, and 100% (2/2) for iopromide. Cross-reactivity was in the range of 59.6%-75.9% between iohexol and iodixanol, 75.0%-77.4% between iohexol and iopromide, and 43.3%-60.0% between iodixanol and iopromide. Only 1/14 patients who were skin test and DPT negative developed a reaction on re-exposure to ICM after testing.Conclusion Objective testing for ICM hypersensitivity, particularly within 6 months of initial exposure, allows the majority of patients to be administered the same or an alternative ICM with no adverse reaction, with iodixanol having the lowest cross-reactivity.