Immediate hypersensitivity reactions to iodinated contrast media despite drug prophylaxis-a comparative retrospective cohort study of breakthrough reactions in Bern (Switzerland) and Seoul (South Korea)

Background: Although several studies deal with breakthrough reactions (BTRs) in patients with contrast media (CM) hypersensitivity reactions, the phenomenon is still unclear. Therefore, this study aimed to analyse in depth patients with BTR in two countries. Methods: We retrospectively analysed the electronic medical records of in- and outpatients (random sample enrolment) from two academic hospitals of tertiary care (Seoul/South Korea, with a special monitoring system exclusively for CM hypersensitivity, and Bern/Switzerland, manually operated) with respect to basic epidemiological data, number of BTRs per patient, and severity grades of severity in follow-up analyses. The study period lasted from 2013 (2000 Bern) to 2017. Results: We identified 445 BTR-patients (91.5% from Seoul) with 691 BTRs (94.5% from Seoul). Most reactions were mild, 11% moderate and 3.9% severe. In Seoul, we found patients with up to 10 BTRs, and in Bern, there were only patients with one BTR. Fatal reactions or deaths did not occur. In most cases, the severity of the BTRs and of the index reactions were identical (80.8%). Mild index reactions remained constant in 90.6%. In contrast, in moderate index reactions the severity decreased/remained identically in 86.8% and increased in 13.2%. In severe index reactions, 55.6% of BTR reactions were severe again, in 44.4% the severity decreased. In 158 BTRs (22.9%) the culprit iodinated contrast medium (ICM) of the index reaction induced the BTR. In the other 482 BTRs (69.8%) the culprit ICM was changed to another Conclusions: To the best of our knowledge, this is the largest study on patients with BTRs, and the first study showing BTRs in two centers in two countries of two continents. The main differences between the two centers result from the different hospital size, the number of patients, and the different documentation [manual (Bern) vs. electronical screening (Seoul)]. BTRs are no contraindications for further ICMapplication. We recommend performing an allergy skin test as basis for the decision-making process of the next contrast-enhanced image-guided examination.