Introduction
With the recent advancement in the field of medical imaging equipment, the use of iodinated low osmolar contrast media (LOCM) as a contrast agent for computed tomography (CT) has substantially increased.1 As a result, LOCM-related adverse reactions, usually classified as toxic and rarely immunologically-mediated hypersensitivity (HSR), have also increased.2
The greatest risk factor for the development of recurrent HSR to contrast media is a previous history of HSR.3,4 Two main strategies have been widely used for managing patients with previous immediate hypersensitivity according to severity: premedication,3, 5-7 and change of the culprit LOCM.8,9 The decision of which among these methods is to be used is based on the severity of the HSR. For decades, premedication has been the primary choice of care across the world for preventing HSR .10-12 However, premedication cannot completely prevent the recurrence of HSR, so called ‘breakthrough reactions (BTRs)’, which occur in up to 17.1% of patients who experienced a previous HSR to LOCM despite premedication.3,13 A previous study reported that changing the culprit LOCM to other one without skin test reduced the recurrence of HSR from 31.1% to 7.6% in mild HSR cases.9 However, there is no defined guideline for choosing a safe alternative LOCM to prevent the recurrent HSR other than avoiding the culprit agent. Therefore, it is of interest how to choose the right and safe alternative LOCM which is non-reactive on systemic re-exposure.
Skin testing to all patients who showed a prior HSR to LOCM is not routinely recommended because of its relatively low sensitivity and an unreliable positive predictive value.15 One option for screening safe alternative(s) for re-exposure to contrast media is skin testing with LOCM.14,15 However, its clinical usefulness is not clearly validated yet and the choice of alternative LOCMs is still unsolved problem since certain combinations of alternate LOCM had no prophylactic effect.8 The cross-reactivity by the common N-(2,3-dihydropoxypropyl) carbamoyl side chains found in LOCMs are believed to be a possible clue into choosing safe alternatives for subsequent re-exposure.18,19 There is, however, currently no standard recommendation for deciding the optimal choice of safe alternative LOCMs based on clinical evidence, such as outcomes of re-exposure to contrast media. The aim of this study was to evaluate the cross-reactivity between LOCMs and the outcomes of LOCM re-administration based on the presence of common carbamoyl side chain in patients who had immediate HSR.