Late elicitation of maculopapular exanthemas to iodinated contrast media after first exposure

Intradermal testing of iodinated contrast media: Should we test up to pure or with diluted compounds only?

BACKGROUND

Intradermal testing (IDT) with iodinated contrast media (ICMs) is an established diagnostic tool in patients with ICM hypersensitivity. Currently, it is unclear which test concentration is the more useful one, up to pure or up to 1:10 diluted ICMs.

METHODS

We searched the literature database PubMed for eligible papers dealing with ICM allergy and their IDT results. We analyzed the data presented by the papers and compared the pooled groups tested with diluted and undiluted ICMs.

RESULTS

We identified 29 eligible original papers, and extracted data of 1137 patients that formed the study population. Although in the cohort tested with diluted ICMs the number of tested ICMs was greater, the percentage of positive tests was significantly less (9.0% vs. 24.7%; P < 0.0001; OR 0.30 [0.26-0.34]). The frequency of positive tested culprit ICMs was also lesser in the group tested with diluted ICMs (31.0% vs. 72.5%; P < 0.0001; OR 0.17 [0.12-0.23]). The number of drug provocation tests (DPTs) was greater in patients with diluted IDTs (374 vs. 89; P < 0.0001; OR 2.54 [1.93-3.36]). We detected an increased sensitivity in patients with undiluted tests (0.774 vs. 0.282) and a nearly identical specificity in both groups (1 vs. 0.983).

CONCLUSIONS

For the first time, we show that IDT up to pure ICM concentrations is superior to using diluted ICMs only. Possibly, we can reduce the number of DPTs when performing IDTs with pure ICMs. In the undiluted group, there were no hints for skin irritations or unspecific test reactions.

Delayed hypersensitivity reaction after oral intake of non-ionic iodinated contrast medium

Following intravenous contrast medium (CM) injection, a small proportion of patients acquires hypersensitivity reactions that occur either immediately or non-immediately (delayed). Although it is now claer that even oral applied CMs are able to cause adverse reactions, many radiologists as well as physicians of other disciplines, still believe that CM-application via the gastrointestinal route does not induce hypersensitivity reactions. Since this kind of misinterpretation may harm the patient, education on this topic is still necessary. Therefore, we describe a case who acquired a delayed hypersensitivity reaction following the oral intake of a non-ionic iodinated CM.

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

Background

Although several papers deal with "cross-reactivity" in patients with iodinated contrast medium (ICM) hypersensitivity reactions (HSRs), there is no in-depth knowledge of this phenomenon. To define ICM-groups as potential reaction partners and to identify any potential clinical relevance in patients with ICM-HSRs.

Methods

The literature database PubMed was searched for eligible papers dealing with ICM-allergy and "cross-reactivity". The data presented by the papers was analyzed and individual patient data was extracted for re-evaluation based on a definition for both 'polyvalent reactivity' and 'cross-reactivity' as well as for chemical structure-dependent ICM-groups.

Results

Twenty-five original papers (with n=340 extracted patients) formed the study population. Incidences of polyvalent reactivity were non-significantly higher than incidences of cross-reactivity (both range from 0% to 100%). Crossover evaluation in reaction pairings (culprit ICM A with ICM B versus culprit ICM B with ICM A) showed concordance of only 30%. Data support rather non-cross-reactivity (individual reaction pattern) than cross-reactivity constellations.

Conclusions

The obtained results favour an individual reaction pattern, rather than a reactivity driven by chemical structures and so-called cross-reactivity.

Adverse reactions during procedures: Hypersensitivity to contrast agents and dyes

OBJECTIVE

This review provides an overview of the literature on hypersensitivity reactions during procedures to commonly used contrast agents and dyes. A synthesis of current knowledge on clinical symptoms, epidemiology and risk factors, pathomechanism, and management of hypersensitivity reactions to these substances is presented.

DATA SOURCES

A literature search was conducted through Medline. Included were peer-reviewed articles written in English between 2000 and 2019.

STUDY SELECTIONS

Relevant clinical studies, experimental studies, and review articles have been selected. Additionally, case reports have been included if they carried significant information about rare clinical forms of hypersensitivity reactions, disease mechanisms, or therapy.

RESULTS

An allergological workup is only indicated for patients with a history of immediate (IHR) and nonimmediate hypersensitivity reactions (NIHR) but not for toxic or unrelated adverse events. Skin tests with or without experimental cellular laboratory tests in patients with previous reactions can provide evidence for an allergic mechanism. Positive skin tests indicating allergy are more common in severe reactions. If the adverse event was allergic, skin testing of alternatives is helpful for the selection of other contrast agents for future procedures. Premedication alone may be insufficient in these cases, and breakthrough reactions occur. For nonallergic reactions, change of contrast agent and premedication is often but not always sufficient to suppress reactions.

CONCLUSION

Patients with previous NIHR or IHR, especially moderate and severe IHR, needing potential re-administration of contrast agents should be skin tested to identify an allergic mechanism as well as alternative agents to be used for future procedures.

Hypersensitivity to contrast media and dyes

This article updates current knowledge on hypersensitivity reactions to diagnostic contrast media and dyes. After application of a single iodinated radiocontrast medium (RCM), gadolinium-based contrast medium, fluorescein, or a blue dye, a hypersensitivity reaction is not a common finding; however, because of the high and still increasing frequency of those procedures, patients who have experienced severe reactions are nevertheless frequently encountered in allergy departments. Evidence on allergologic testing and management is best for iodinated RCM, limited for blue dyes, and insufficient for fluorescein. Skin tests can be helpful in the diagnosis of patients with hypersensitivity reactions to these compounds.