Value of skin testing in iodinated contrast media hypersensitivity

Published online: January 19, 2018

Iodinated contrast media (ICM) can cause hypersensitivity reactions, both immediately (occurring ≤1h after administration) and non-immediately (occurring from >1h to several days after administration). A minority, and typically those with a severe clinical presentation, are considered to be allergic and can be identified using skin testing. However, the management of ICM hypersensitivity has been a matter of debate and often complete avoidance of all different ICMs, premedication or provocation testing is proposed.

In a recently published article in The Journal of Allergy and Clinical Immunology: In Practice, Chiriac and coworkers investigated the value of skin testing in patients with a previous ICM hypersensitivity reaction to guide the choice for future ICM rechallenge. By contacting 597 patients who underwent skin testing for potential ICM hypersensitivity from 1998-2015 (enrolled in the French Drug Allergy and Hypersensitivity Database, the largest cohort to date) they evaluated the tolerance of re-exposure to a negatively skin tested ICM.

Around two-thirds of patients had a history of immediate ICM hypersensitivity, of whom anaphylaxis (grade 2 or more) was present in around half. Skin testing was able to identify a subgroup (13%) with an allergy to at least one ICM. The authors found that re-exposure to a negatively skin-tested ICM had occurred in 39% of all investigated patients and was tolerated in the majority (93%). In total, 16 patients had a reaction upon re-exposure which was milder or similar compared to the initial event in most cases. Those with a confirmed ICM allergy by skin testing who were rechallenged with a skin-test-negative alternative ICM tolerated this re-exposure. In this study premedication was not systematically advised, although a subgroup of patients (at least 21%) had received H1-antihistamines before re-exposure. Another observation, in line with daily practice, was that skin testing was often delayed beyond the recommended interval of 1-6 months after the initial event.

This report demonstrates that skin testing for potential ICM hypersensitivity can identify safe alternative(s) for ICM re-exposure and supports the idea of an allergologist-driven, clinical history- and skin-test-based approach to guide ICM re-exposure in patients with a prior ICM hypersensitivity reaction. In patients with a confirmed ICM allergy potential skin-test-negative alternatives could be identified, and in those with all negative skin tests, reactions upon re-exposure were infrequent, mostly milder, and considered non-allergic. Re-exposure was recommended in a safe environment and remained contraindicated in severe delayed-type drug allergies (such as DRESS). Finally, the study was not designed to evaluate the role of premedication. Premedication can probably reduce symptoms in non-allergic hypersensitivity reactions as the authors observed in some patients, but. there is ample evidence that premedication is insufficient to prevent severe IgE-mediated reactions, arguing for a stepwise approach using skin testing to identify this subset of patients and to provide them with safe alternatives, rather than relying on premedication only.

The Journal of Allergy and Clinical Immunology: In Practice is the official scientific journal of the AAAAI, focusing on practical information for the practicing clinician.

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