D1.34 - Hypersensitivity Reactions to Iodinated and Gadolinium-Based Contrast Media: Clinical and Epidemiological Insights

Drug hypersensitivity reactions (DHRs) to iodinated contrast media (ICM) and gadolinium-based agents (GBCA) are a growing concern due to widespread use. Immediate reactions (0.5%-3%) range from urticaria to anaphylaxis, while delayed reactions (up to 1%) mainly manifest as exanthema. Despite advances in this area, significant challenges remain in understanding cross-reactivity and identifying safe alternatives.

Objetive: To characterise the clinical profiles and the allergological studies in patients with reactions to ICM and GBCA, aiming to optimize diagnostic and therapeutic strategies.

Descriptive cross-sectional study of patients with adverse reactions to radiologic contrast media (ICM and GBCA), evaluated in our Allergy Department between January 2023 and December 2024. 

A total of 49 patients (69% female, n=34) with DHRs to radiologic contrast media were included. Twenty-nine patients experienced reactions to ICM and 20 to GBCA. The mean age at the reaction was 52.8 [24–79] years. Atopy was identified in 20% (n=10), and oncological comorbidities in 51% (n=25).

Among ICM-related DHRs, 34% (n=10) exhibited non-specific histamine-releasing reactions, 17.5% (n=5) with mild hypersensitivity reactions (grade 1-2 EAACI), and 27.5% (n=8) experienced anaphylaxis (grades 3–5 EAACI). Additionally, 21% (n=6) had delayed hypersensitivity reactions, including a case of acute generalized exanthematous pustulosis. Non-ionic iodinated agents iohexol and iodixanol were involved in 65% (n=19) of cases.

In GBCA-related DHRs, 75% (n=15) developed anaphylaxis (grades 3–5 EAACI), with 35% (n=7) of anaphylactic shocks. Gadobutrol was most frequently involved. Notably, 65% (n=10) of these GBCA-related anaphylaxis occurred without prior exposure, suggesting a non-IgE-mediated mechanisms like mast cell activation via MRGPRX2.

In the allergy workup, intradermal skin test was positive in 31 patients, 48% showing multiple sensitivities across physicochemical groups, suggesting a pattern of polyvalent reactivity rather than classical cross-reactivity. Negative skin tests guided the selection of a safe alternative contrast, which was subsequently confirmed through intravenous drug challenge in 60% (n=29) of the sample.

Hypersensitivity to contrast media shows diverse clinical manifestations, highlighting the need for improved phenotyping to explore underlying mechanisms and better understand cross-reactivity patterns.