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Three Part Question

What is the risk of an [adverse reaction] in [patients with iodine or shellfish allergies] who [receive radiocontrast media]?

Clinical Scenario

An emergency department patient needs a computed tomography angiogram to rule out a pulmonary embolism. The patient has a shellfish allergy noted on the medical record and you wonder if it is safe for the patient to receive intravenous radiocontrast.

Search Strategy

Medline 1966-07/19 using PubMed, Cochrane Library (2019), Google Scholar, and Embase
[(contrast media/adverse effects OR contrast media reactions) AND (exp shellfish/adverse effects OR exp iodine/adverse effects OR exp food Hypersensitivity)]. Limit to English language.

Search Outcome

199 studies were identified; one systematic review article specifically addressed the clinical question.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Schabelman E Nov 2010 United States	6 articles were included	Systematic review	Risk of contrast reaction in all cases compared to persons with known allergies to seafood, food allergens, asthma, and prior contrast reactions	Allergies to seafood does not increase the risk of reaction to contrast any more than a history of other allergies or asthma	Several studies are based on high osmolar contrast medium which has been largely replaced by low osmolar contrast medium

Comment(s)

Millions of imaging studies using radiocontrast media are conducted each year, providing vital information for patient care. Adverse reactions to contrast media are rare and are mostly dependent on the osmolar weight of the contrast media. The risk of reaction increases with a history of asthma or food allergy including eggs, milk, chocolate, fruit and seafood. Seafood does not predispose to a greater risk with regards to severity of reaction or incidence of reaction compared to any other allergy. Iodine is found throughout our bodies in thyroid hormones and amino acids and cannot be an allergen.

Clinical Bottom Line

There is no evidence that allergy to shellfish or iodine alters the risk of reaction to intravenous contrast more than any other allergy.

References

1. Schabelman E, Witting M The relationship of radiocontrast, iodine, and seafood allergies: a medical myth exposed J Emerg Med 2010 Nov;39(5):701-7