Radiocontrast media hypersensitivity: skin testing differentiates allergy from non-allergic reactions and identifies a safe alternative as proven by intravenous provocation

Summary Background Hypersensitivity reactions occurring within minutes after intravascular injection of iodinated radiocontrast media (RCM) are common and have been previously considered to be non-allergic. However, in the last decades, evidence is increasing that also genuine RCM allergy may present as either full-blown anaphylaxis or delayed exanthematous skin reaction. Objectives We aimed to assess whether allergy diagnostics including skin and provocation testing can differentiate between non-allergic and allergic RCM hypersensitivity by identifying the causative RCM as well as tolerated alternative RCM. Methods We retrospectively evaluated clinical and diagnostic data from 45 consecutive patients with RCM hypersensitivity. Results Immediate non-allergic RCM hypersensitivity was diagnosed in 21 patients, immediate-type RCM allergy in 11, delayed-type RCM allergy in 11, and delayed-type iodine allergy in two. All patients with immediate-type RCM allergy had a history of moderate to severe anaphylaxis. Eleven of 13 patients with delayed-type allergic reactions including the two cases of iodine allergy suffered from maculopapular exanthem developing several hours to days after exposure, one was a systemic hypersensitivity syndrome and one a fixed drug eruption. Of 18 RCM-allergic patients tested, all tolerated an alternative RCM in the intravenous provocation. Conclusions The diagnostic sensitivity of intradermal RCM testing to identify allergic patients is high in both, immediate-type and delayed-type RCM allergy. Intravenous provocation with a skin test-negative RCM is safe and enables identification of a tolerated alternative RCM. Additional skin testing of iodine solution is required to identify patients with iodine allergy.