Skin Testing for Suspected Iodinated Contrast Media Hypersensitivity

Abstract

The management of iodinated contrast medium (ICM) hypersensitivity has been a matter of debate. Skin testing to identify a subgroup of ICM allergic patients has been proposed, in addition to complete avoidance, provocation testing, or premedication. The objective of this study was to assess the negative predictive value (NPV) of skin testing for ICM. Patients with a hypersensitivity reaction to ICM who underwent skin testing during a 13.5-year period at a single center were evaluated for re-exposure to a negatively skin-tested ICM. Premedication, consisting of second-generation H1-antihistamines twice a day 48 hours before the examination, was advised only for patients with mast cell disorder or chronic urticaria who had negative skin tests. A total of 597 patients tested for 423 (70.9%) immediate, 118 (19.7%) nonimmediate, and 56 (9.4%) hypersensitivity reactions with undetermined chronology were included. Eighty (13.4%) patients were skin test positive. Re-exposure to ICM occurred in 233 (39.0%) patients and was tolerated in 16 of 17 (94.1%) with at least 1 positive skin test and 201 of 216 (93.1%) with all negative skin tests. Reaction intensity was similar in 4, milder in 10, unknown in 1, and worse in 1 patient although this reaction was deemed to be nonallergic in hindsight. Premedication was administered in 20.7% of patients and associated with more reactions (19.4% vs 5.7%, P= .01). The overall NPV of skin testing for ICM was 93.1% (95% confidence interval [CI] 89.1% to 96.0%), and for immediate and nonimmediate hypersensitivity reactions 94.2% (95% CI 89.6% to 97.2%) and 86.1% (95% CI 72.1% to 94.7%), respectively. We cannot exclude some challenges occurred with a different than the initial culprit ICM, possibly overestimating the NPV. Skin testing for potential ICM hypersensitivity can identify safe alternative(s) for ICM re-exposure especially in patients with an immediate hypersensitivity reaction and/or skin test-proven ICM drug allergy. Reactions on re-exposure were infrequent, mostly milder, and occurred in some patients despite premedication.