Iodinated Contrast Media and the Alleged “Iodine Allergy”: An Inexact Diagnosis Leading to Inferior Radiologic Management and Adverse Drug Reactions

Abstract

ZUSAMMENFASSUNGZiel Ziel dieser Studie war die Überprüfung der Hypothese, dass die ungenaue Diagnose "Jodallergie" für Patienten unter radiologischen Routinebedingungen möglicherweise gefährlich ist. ABSTR ACTPurpose To test the hypothesis that the incomplete diagnosis "iodine allergy" is a possibly dangerous concept for patients under routine radiologic conditions. Materials and Methods 300 patients with a history of an "iodine allergy" were retrospectively screened and compared with two age-, sex-, and procedure-matched groups of patients either diagnosed with a nonspecific "iodine contrast medium (ICM) allergy" or an allergy to a specific ICM agent. For all groups, the clinical symptoms of the This document was downloaded for personal use only. Unauthorized distribution is strictly prohibited. most recent past adverse drug reaction (ADR), prophylactic actions taken for subsequent imaging, and ultimate outcome were recorded and analyzed.Results The diagnosis "iodine allergy" was not otherwise specified in 84.3 % patients. For this group, in most cases, the symptoms of the previous ADRs were not documented. In contrast, the type of ADR was undocumented in only a minority of patients in the comparison groups. In the group of patients with an "iodine allergy" the percentage of unenhanced CT scans was greater than within the other two groups (36.7 % vs. 28.7 %/18.6 %). ADRs following prophylactic measures were only observed in the "iodine allergy" group (OR of 9.24 95 % CI 1. 16 -73.45; p < 0.04).Conclusion This data confirms the hypothesis that the diagnosis "iodine allergy" is potentially dangerous and results in uncertainty in clinical management and sometimes even ineffective prophylactic measures.Key points ▪ The term "iodine allergy" is imprecise, because it designates allergies against different substance classes, such as disinfectants with complexed iodine and contrast media containing covalently bound iodine. ▪ There is a clear correlation between the exactness of the diagnosis -from the alleged "iodine allergy" to "contrast media allergy" to naming the exact culprit CM -and the quality of documentation of the symptoms. ▪ Management of patients diagnosed with "iodine allergy" was associated with uncertainty leading to unenhanced scans and sometimes unnecessary prophylactic actions. ▪ The term "iodine allergy" should be omitted, because it is potentially dangerous and can decrease the quality of radiology exams.

Incidence and Risk Factors of Immediate Hypersensitivity Reactions Associated With Low-Osmolar Iodinated Contrast Media: A Longitudinal Study Based on a Real-Time Monitoring System

“…A previous history of hypersensitivity to LOCM is a major risk factor for further hypersensitivity [30], and several preventive strategies have been used in at-risk patients. Accurate documentation of the contrast agent that induced the response and history of iodine allergy should be evaluated [31], because a previous history of hypersensitivity is the main risk factor. Premedication before injection of the LOCM is widely used to lower the incidence of hypersensitivity in patients with previous hypersensitivity, and some studies suggest that stratifying premedication according of immediate hypersensitivity to LOCM gradually increased with the number of previous exposures (P for trend <.001, Figure 2A).…”

Cross-reactivity among iodinated contrast agents: should we be concerned?

“…We need the differentiation between polyvalent reactivity and cross-reactivity, because the cross-reactivity does not depend on the iodine atom. In other words, the alleged "iodine allergy" does not exist (1,5). Moreover, the differentiation between polyvalent and cross-reactivity is one focus of our study.…”

“…Most papers dealing with this topic utilized no definition of the term, and referred to it synonymously with the term polyvalent positive reactions (3,8,26,30). However, this incorrectly implicates the iodine atom as being responsible for the reactivity, thereby resuscitating the old, incorrect concept of the "iodine allergy" (1,5).…”

“…Currently, iodinated contrast media (ICM) are most common used drugs in radiology. Although exact data are unknown, an estimated number of several hundred million doses worldwide per year are administered with increasing frequency (1). This large number of ICMdoses makes hypersensitivity reactions (HSRs) induced by ICMs a challenge in radiology, despite its low incidence of 0.004-3.0% (2,3).…”

Limited duration of hypersensitivity reactions to contrast and exact documentation of such adverse events

“…Take home messages: (1) the duration of CM-induced HRs is limited and (2) the more exact the documentation, the more safe the subsequent CM application 5…”