How to predict, prevent allergic reactions to CT contrast agents

Patients with a family or personal history of allergic reactions to contrast agents are at risk of experiencing similar reactions in the future, according to a new study published in Radiology.

The authors explored data from more than 196,000 patients who underwent CT scans with iodinated contrast media (ICM). All scans took place at one of seven participating institutes in 2017. The average patient age was 59 years old.

Overall, 0.73% of patients experienced a hypersensitivity reaction (HSR). Most HSRs were “mild,” but 16.8% were “moderate to severe.” Factors that could help predict an HSR included a patient’s personal or family story of ICM-related HSRs, hyperthyroidism, drug allergies or asthma.

Switching to an ICM with a different safety profile or using antihistamines, the authors found, helped with reducing reactions from recurring.

“We wanted to emphasize in our study the importance of premedication and change of iodinated contrast media type as useful preventive measures to prevent recurrent hypersensitivity reaction,” co-lead author Min Jae Cha, MD, from the department of radiology at Chung-Ang University Hospital in Seoul, South Korea, said in a prepared statement. “Hypersensitivity reactions to iodinated contrast media are not rare, but many of them are still preventable.”

The finding that patients may have a genetic predisposition to ICM-related HSRs could help researchers limit these reactions, but it will take a significant amount of effort focused on collecting data.

“We hope that we can establish a systematic nationwide integrated registry for ICM-related HSRs in Korea soon, and our study could be a first step toward that goal,” Cha said in the same statement. “Large-scale and long-term registries involving continuous data collection with standardized protocols will help us unravel all aspects of the contributors to the occurrence and recurrence of hypersensitivity reactions to iodinated contrast media.”