Contrast media skin tests

Skin test sensitivity—the percentage of skin test-positive patients showing a typical hypersensitivity reaction after administration of contrast media skin test specificity—ftercentage of negative controls with a positive skin test to contrast media See Sect. 4.2.2 See Sect. 4.2.3 See Sect. 4.2.4... 

In 32 patients with a history of rashes after injection of iodinated contrast media, skin tests in six cases strongly suggested a delayed-type allergic hypersensitivity to three different contrast agents in four patients alternative non-ionic monomers were identified by controlled challenge tests... 

Numerous positive delayed skin tests in patients with contrast medium-induced non-immediate skin reactions have been reported when the patients were tested with the culprit contrast medium [summarized in 1]. In a large European multicenter study, 37% of patients with non-immediate reactions were positive in delayed IDEs and/or patch tests [13]. The majority of the patients also reacted to the culprit contrast medium and also to other, structurally similar RCM. Notably, in more than 30% of those skin test-positive patients a RCM had been administered for the first time. Thus, there is a lack of a sensitization phase. Again it may be hypothesized that these previously non-exposed patients may have already been sensitized. Different patterns of RCM cross-reactivity indicate that several chemical entities could be involved. No positive skin tests have been obtained with other contrast medium excipients, such as ethylenediaminetetraacetic acid (EDTA), and only rarely patients have been found to react to inorganic iodide. 

As always, a meticulously recorded and studied history is desirable, but additional clinical and laboratory tests can contribute greatly to an accurate diagnosis and help to identify the mechanism(s) of the reaction. Skin tests, detection, and quantitation of released mediators and serum IgE antibodies may all contribute to establishing a more precise diagnosis of an adverse response to an iodinated contrast medium. 

Evidence that immediate reactions to a contrast medium is IgE antibody mediated is based largely on skin test results with or without tryptase measurements and very occasionally serum IgE and basophil activation tests. Delayed reactions mainly manifest as exan-thematons skin eruptions. They are mediated by antigen-specific effector T cells with as yet poorly defined cytokine involvement. 

Kelly, J. F. and Patterson, R. (1974) A complication of skin testing with iodinated radio-graphic contrast medium. Radiology, 110, 353. 

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