D1.260 - Hypersensitivity to Iodinated Contrast Media: Diagnostic Evaluation and Re-exposure Outcomes

Iodinated contrast media (ICM) are widely used due to their safety profile and despite rare, hypersensitivity reactions (HR) can occur. This study characterizes the allergological workup in patients with suspected ICM HR and evaluates re-exposures post-diagnosis.

Retrospective analysis of patients referred (1/2012–12/2024) with suspected ICM HR. Diagnosis was confirmed based on a suggestive clinical history(CH) and positive skin tests (ST) [skin prick tests (SPT), intradermal tests (ID), patch tests (PT)], with or without positive basophil activation test (BAT) or lymphocytic transformation test (LTT), or a positive drug provocation test (DPT). Diagnosis was considered probable based on a suggestive CH and positive BAT/LTT, and excluded following negative DPT. Clinical records were reviewed, and patients were contacted to assess re-exposure outcomes.

A total of 129 patients were included: 57% female, mean age 59 ± 15 years, and 10% atopic. Iopromide was the most implicated agent (66%). Clinical manifestations included skin reactions (67%), anaphylaxis (17%), and malaise (5%). HRs were immediate(I) in 67% (n=87) and non-immediate(NI) in 33% (n=42). Thirty-five patients did not complete the study (18 ongoing and 17 refused).

Among 62 patients with I HR who completed study, diagnosis was excluded in 41 and confirmed in 22: 12 based on DPT, 10 on ID (2 with positive BAT). ID negative predictive value(NPV) was 77%.

Among 31 patients with NI HR with completed study, diagnosis was confirmed in 18 (10 based on DPT, 2 on ST/LTT, 6 on ST), considered probable in 3 (based on LTT), and excluded in 10. ID NPV was 44% and PT NPV was 44%.

Of 40 patients with confirmed HR, 3 were re-exposed to the same ICM implicated in the initial HR. Two patients experienced reactions: 1 with anaphylaxis (initial I RH) and other with cervical edema and oropharyngeal swelling hours after administration (initial NI RH). The 3^th patient had no reaction.

Among 51 patients with excluded HR, 25 were re-exposed: 1 developed urticaria/angioedema with iopromide (initial reaction to ioversol, DPT negative). Ten patients with prior suspected HR avoided ICM despite allergological exclusion of RH.

CH alone overestimates HR. Diagnosis relied on ST and/or DPT for I and NI HR. ID showed moderate NPV for I HR but low NPV for NI HR, indicating false negatives. Re-exposure in confirmed cases carries significant recurrence risk, while unnecessary avoidance persists despite negative testing. The DPT proved to be an important and reliable diagnostic tool for excluding HR, as nearly all patients re-exposed to MCI after a negative DPT did not exhibit any type of reaction.