Biphasic, refractory, and life-threatening anaphylactic reactions to iodinated contrast media: A 10-year...

Iodinated contrast media (ICM) is widely used in computed tomography (CT) imaging, with approximately 120 million doses administered globally annually. Although generally safe, ICM-induced anaphylactic reactions remain a clinical concern.

To evaluate the frequency of anaphylactic reactions to ICM during contrast-enhanced CT imaging and to classify reactions as monophasic, biphasic, refractory, and life threatening.

We performed a retrospective single-center observational study (January 2014-November 2024) including outpatient, inpatient, and emergency settings. No age limits were imposed after manual chart review anaphylaxis cases were included if they met National Institute of Allergy and Infectious Diseases/Food Allergy and Anaphylaxis Network anaphylaxis diagnostic criteria. Cases were categorized as monophasic, biphasic, refractory (requiring ≥3 appropriate doses of epinephrine or initiation of an intravenous epinephrine infusion along with symptom-directed medical management), or life threatening (Dribin grade 5 severity). Descriptive statistics and 95% CIs were calculated.

A total of 702,917 CT scans involving ICM were performed, and 143 patients with anaphylaxis were included. The overall incidence of ICM-induced anaphylaxis was 20.3 cases per 100,000 scans (95% CI: 17.2-24.0) and 47.9 cases per 100,000 patients (95% CI: 40.5-56.6). There were 4 cases of biphasic reactions (3%, 95% CI: 1%-7%), 14 cases of refractory anaphylaxis (10%, 95% CI: 6-16), and 19 cases of life-threatening anaphylaxis (13%, 95% CI: 8-20), including 1 fatal reaction.

Although ICM-induced anaphylaxis is rare, a substantial proportion of cases can be severe, underscoring the need for rapid recognition and treatment.