Biphasic, Refractory, and Life-Threatening Contrast Reactions: Key Findings from a Decade of Iodinated Contrast Safety Data

A newly published 10-year retrospective analysis provides one of the most extensive datasets to date on the frequency and severity of anaphylactic reactions to iodinated contrast media (ICM). Authored by Gao, Lu, Saadi Neto, McDonald, et. al, the study was published online on November 16, 2025 in the Annals of Allergy, Asthma & Immunology. The analysis covers CT contrast administrations from January 2014 through November 2024 across inpatient, outpatient, and emergency settings at a single large U.S. institution.

For imaging centers and radiology groups evaluating emergency-readiness and supervision workflows, the findings reinforce an increasingly important message: while severe contrast reactions are rare, they demand reliable, rapid response systems, regardless of whether supervision is on-site or virtual.

Publication Details and Study Design

The study, “Biphasic, Refractory, and Life-threatening Anaphylactic Reactions to Iodinated Contrast Media: A 10-Year Retrospective Analysis,” reviewed an extraordinary dataset: 702,917 CT scans performed with iodinated contrast over a decade. After a detailed manual chart review using NIAID/FAAN diagnostic criteria, the authors identified 143 confirmed cases of anaphylaxis, spanning outpatient, inpatient, and emergency settings and including patients of all ages. Each reaction was then classified into one of four categories—monophasic, biphasic, refractory, or life-threatening—based on clinical course and treatment requirements, with life-threatening events defined using the Dribin grade 5 severity scale. The analysis included descriptive statistics and confidence intervals to give a clearer picture of how often each reaction type occurs in real practice.

Over the ten-year period, the overall incidence of iodinated contrast–induced anaphylaxis was low—20.3 cases per 100,000 scans, or 47.9 cases per 100,000 patients—but the distribution of severe reactions carries important operational implications. While most reactions were monophasic, 3% were biphasic, 10% were refractory, and 13% were life-threatening, including one fatal case. Life-threatening reactions occurred at a rate of 2.7 per 100,000 scans, with a fatality rate of 0.14 per 100,000 scans. Because these numbers are drawn from such a large sample, they serve as some of the most reliable real-world incidence estimates available and help refine what earlier, smaller studies suggested.

The study also revealed striking variation in how reactions were treated, particularly in the use of epinephrine—the first-line therapy for anaphylaxis. Only 50% of patients received epinephrine, even though 76% received antihistamines and 55% received corticosteroids. Emergency departments administered epinephrine far more consistently than inpatient or outpatient settings, with nearly double the rate of use (risk ratio 1.84). This pattern suggests that recognition of anaphylaxis and comfort with guideline-based treatment still differ across clinical environments, even within a single institution.

Understanding the severity categories is more than academic. Biphasic reactions may recur after a symptom-free interval, which means patients need extended observation. Refractory reactions demand familiarity with repeated intramuscular epinephrine and IV infusions—interventions that many outpatient centers do not routinely perform. Life-threatening reactions require immediate escalation because airway compromise, hemodynamic instability, and neurologic decline can emerge within minutes. These distinctions highlight why supervising physicians must be reliably available for rapid consultation, whether physically present or connected through real-time audio-video technology.

The authors acknowledge several limitations: the single-center, retrospective design; the small absolute number of severe events; dependence on subjective diagnostic classification; and inconsistent documentation after patient discharge. Even so, the dataset is one of the most comprehensive published to date and offers a rare, high-volume view of contrast reaction patterns in modern imaging practice.

Relevance t o Virtual Supervision in 2026 and Beyond

This study reinforces several operational principles that align with evolving ACR and CMS supervision policy:

1. Severe reactions remain rare, but unpredictable. Even with premedication, reaction trajectories vary, emphasizing preparedness.

2. Timely physician input matters more than physical proximity. CMS’s 2026 PFS and OPPS rules affirm real-time audio-video as meeting direct supervision requirements for contrast studies. Studies like this one support that rationale.

3. Standardized emergency protocols reduce variation. The variation in epinephrine use across settings highlights the importance of repeatable, system-level training—something virtual supervision models can help standardize across multiple sites.

Tether Supervision’s contrast supervision model is engineered around these operational realities: structured contrast-readiness workflows, on-demand physician availability, and documented response procedures designed to align with ACR accreditation expectations and CMS supervision definitions.

This large-scale retrospective analysis strengthens the evidence base for understanding the true severity distribution of iodinated contrast reactions. While catastrophic events remain rare, the proportion of refractory and life-threatening reactions underscores the importance of readiness, rapid escalation, and consistent emergency protocols—regardless of whether supervision is delivered on-site or via virtual direct supervision.

Citation

Gao H, Lu L, Saadi Neto E, McDonald JS, McDonald RJ, Mullan AF, Hagan JB, Li JT, Campbell RL. Biphasic, Refractory, and Life-threatening Anaphylactic Reactions to Iodinated Contrast Media: A 10-Year Retrospective Analysis. Ann Allergy Asthma Immunol. Published online November 16, 2025. PMID: 41260486. DOI: 10.1016/j.anai.2025.11.004.