Published online: April 10, 2019
Hypersensitivity reactions following intravenous injection of iodinated radiocontrast media (RCM) are not uncommon. The great majority are non-allergic reactions, which are generally mild with symptoms remaining confined to the skin, namely flushing and generalized urticaria. Premedication is recommended for susceptible individuals and effective to prevent future reactions.
The study by Trautmann et al. published in The Journal of Allergy and Clinical Immunology: In Practice aimed to differentiate between RCM hypersensitivity reactions due to non-allergic mechanisms, immediate-type allergy, and delayed-type allergy. Allergy testing (intradermal skin testing) was evaluated in order to identify the culprit and possibly cross-reactive RCM. In case of allergy to one or more specific RCM, authors performed further testing (provocation testing) to identify a tolerated alternative RCM.
The diagnostic sensitivity of skin (intradermal) testing to identify allergic patients is high in both immediate-type RCM allergy and delayed-type RCM allergy. Immediate-type, presumably IgE-mediated RCM allergy is the underlying mechanism of RCM-induced full-blown anaphylaxis with systemic signs besides urticaria, such as dysphonia or hoarseness, deep cough or wheezing, respiratory stridor, drop in blood pressure, abdominal cramps, vomiting, somnolence, impaired vision, and loss of consciousness. Delayed-type RCM allergy commonly causes a measles-like exanthem with an onset hours to days after RCM injection. Intravenous provocation with a skin test-negative RCM appears safe in both delayed-type and immediate-type RCM allergy and enables identification of a tolerated alternative RCM, which can be used in future radiological examinations.
RCM allergy is comparatively rare, but a potential cause of severe clinical reactions. Cross-reactivity between different RCM is common, but intravenous provocation with skin test-negative RCM is safe and reliably identifies a tolerated alternative.
The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.