Hypersensitivity reactions and contrast medium injection: are they always related?

Hypersensitivity (allergic or non-allergic) reactions that occur after contrast medium (CM) injection are usually related to the CM. Recent studies, and case reports lack the analysis of alternate causes that could be also responsible in individual cases.We investigated the individual relevant factor/causative agent of adult patients with hypersensitivity reactions that occurred in radiological units during CM-enhanced procedures (CT, angiography, urography, or MR-examinations). Both immediate and non-immediate (delayed) reactions were included. To find out the relevant agent a detailed patients' history was carefully analyzed. In addition, the records were retrospectively reviewed, and if indicated and possible laboratory (e.g. basophil activation test) and skin tests (e.g. prick) and/or provocations with CM-injections under routine conditions were performed.38 patients (men n=21) suspected for CM-hypersensitivity reactions were identified. These reactions were in most cases mild (n=21), moderate reactions occurred in 13 cases, and four patients had severe reactions. In 28 patients the reactions were induced by the CM (iodinated CM in 25 cases). Four patients had reactions that were not CM-related (latex allergy, adenosine reaction, vasovagal reaction, unknown cause) and in six cases the reaction was partly CM-related (immunological activation was present due to the patients' diseases).Our data support the hypothesis that in CM-enhanced procedures not only contrast materials but also a broad range of other factors may also induce hypersensitivity reactions. Therefore, the number of CM-induced hypersensitivity is smaller than initially suspected. The knowledge of the cause of a reaction is essential to effectively prevent its recurrence and to improve safety aspects in patients undergoing CM-injection. Larger trials should be performed to more specifically assess alternate causes in patients who acquire hypersensitivity reactions in CM-enhanced diagnostic procedures.