Skin testing in patients with hypersensitivity reactions to iodinated contrast media – a European multicenter study

Abstract

Skin testing in patients with hypersensitivity reactions to iodinated contrast media -a European multicenter study Iodinated contrast media (CM) are highly concentrated solutions of iodinated benzene derivatives, used to enhance X-ray procedures (1). Although these products are regarded as relatively safe, they are known to cause both immediate ( £ 1 h) and nonimmediate (>1 h) hypersensitivity reactions in susceptible individuals (2).Background: Iodinated contrast media cause both immediate and nonimmediate hypersensitivity reactions. The aim of this prospective study was to determine the specificity and sensitivity of skin tests in patients who have experienced such reactions. Methods: Skin prick, intradermal and patch tests with a series of contrast media were conducted in 220 patients with either immediate or nonimmediate reaction. Positive skin tests were defined according to internationally accepted guidelines. Seventy-one never-exposed subjects and 11 subjects who had tolerated contrast medium exposure, served as negative controls. Results: Skin test specificity was 96-100%. For tests conducted within the time period from 2 to 6 months after the reaction, up to 50% of immediate reactors and up to 47% of nonimmediate reactors were skin test positive. For immediate reactors, the intradermal tests were the most sensitive, whereas delayed intradermal tests in combination with patch tests were needed for optimal sensitivity in nonimmediate reactors. Contrast medium cross-reactivity was more common in the nonimmediate than in the immediate group. Interestingly, 49% of immediate and 52% of nonimmediate symptoms occurred in previously unexposed patients. Many of these patients were skin test positive, indicating that they were already sensitized at the time of first contrast medium exposure. Conclusions: These data suggest that at least 50% of hypersensitivity reactions to contrast media are caused by an immunological mechanism. Skin testing appears to be a useful tool for diagnosis of contrast medium allergy and may play an important role in selection of a safe product in previous reactors.

Clinical Practice Guidelines for Diagnosis and Management of Hypersensitivity Reactions to Contrast Media

“…Several studies support the finding of specific IgE-mediated immunological mechanisms in immediate reactions, and positive skin test results with ICM have been reported in patients who experience severe immediate reactions [14][15][16]. Some of these patients also react to other ICM to which they had not been previously exposed, probably because the core chemical structure common to ICM is part of the antigenic determinant and thus induces cross-reactivity.…”

“…Several studies of nonimmediate reactions to ICM have shown skin tests to be positive with the ICM involved [15,60,67,68] and with other ICM with similar chemical structures [15,19].…”

“…Some patients react to ICM upon their first exposure [15,19]. One explanation could be that these patients may have been previously sensitized by structurally related molecules.…”

“…Immediate reactions have long been attributed to non-IgEmediated mechanisms [9], although there is growing evidence that tryptase levels increase after the reaction. Furthermore, positive skin test or basophil activation test results could support an IgE-mediated mechanism in some cases [13][14][15][16][17]. The prevalence of nonimmediate hypersensitivity reactions has increased significantly in the last decade, whereas that of immediate reactions has decreased, with the result that nonimmediate reactions are now more frequent than immediate reactions [18].…”

Clinical Pharmacology, Uses, and Adverse Reactions of Iodinated Contrast Agents: A Primer for the Non-radiologist

“…Although skin testing may be used to confirm a reaction to an ICA, the sensitivity of the test may depend on the duration of the administration of the test compared with the timing of initial ICA exposure. 47 Furthermore, a negative predictive value of 97% suggests that skin testing may be more useful to rule out a reaction to ICAs. 48 In patients with a prior reaction, ICAs should be avoided, if possible.…”