Hypersensitivity to iodinated contrast media: diagnostic evaluation and re-exposure outcomes

Background. Iodinated contrast media (ICM) are widely used and generally safe, although hypersensitivity reactions (HSR) may occur. This study aimed to characterize the allergological workup of patients with suspected ICM HSR and evaluate outcomes after re-exposure. Methods. We conducted a unicentric  retrospective study of patients referred between January 2012 and December 2024 for suspected ICM HSR. Diagnosis was confirmed by suggestive clinical history (CH) with positive skin tests (skin prick, intradermal, and/or patch tests), with or without positive basophil activation test (BAT) or lymphocyte transformation test (LTT), or by a positive drug provocation test (DPT). Diagnosis was considered probable with suggestive CH and positive BAT/LTT, and excluded after negative DPT. Clinical records were reviewed, and patients were contacted to assess re-exposure outcomes. Results. A total of 129 patients were included (57% female; mean age 59 ± 15 years); 10% were atopic. Iopromide was the most frequently suspected agent (66%). Reactions were immediate in 67% and non-immediate in 33%, mainly cutaneous (67%). Among those completing the workup (n = 94), immediate HSR was excluded in 40 patients and confirmed in 22 (NPV 77%). Non-immediate HSR was confirmed in 18, considered probable in 3, and excluded in 10; intradermal and patch tests NPV was 44%. Among 40 patients with confirmed HSR, three were re-exposed to the culprit ICM and two reacted. Of 51 patients with excluded HSR, 25 were re-exposed, with one mild reaction. Conclusions. CH alone overestimates ICM HSR. Diagnosis relies on skin tests and particularly DPT, which supported exclusion of HSR, when negative.