ACR Challenges FDA Guidance on Thyroid Monitoring for Young Children Exposed to Iodinated Contrast Media

The American College of Radiology (ACR) has issued a new statement that challenges a March 2022 guidance from the Food and Drug Administration (FDA) about thyroid monitoring in children three years old and younger within three weeks of exposure to iodinated contrast media (ICM).

The ACR statement, published in the Journal of the American College of Radiology, raises several questions about the literature used to support the FDA guidance.

Out of the 11 studies cited by the FDA, the authors of the ACR statement pointed out the following:

• Two of the cited studies found no impact on thyroid function from ICM exposure.

• Two separate studies found that ICMs are “well tolerated in premature and term infants, with only transient alterations in thyroid function observed.”

• The largest control group, among the three prospective studies that had control groups, was comprised of 26 patients.

• The majority of the FDA-cited studies prohibited extrapolation of the findings to a broader pediatric population due to a focus on pediatric subpopulations including five studies involving neonates or infants with congenital heart disease, three studies involving term neonates and four studies that focused on premature infants with low birth weight.

“At this time, no convincing scientific evidence exists to support routine thyroid function testing in children older than 3 months with or without congenital heart disease after intravascular ICM,” wrote Jonathan R. Dillman, MD, MSc, associate chief of research in the Department of Radiology and the medical director of the Imaging Research Center within the Division of Radiology at the Cincinnati Children’s Hospital Medical Center, and colleagues.

The authors of the ACR statement also noted potential adverse consequences of the FDA guidance, including exposure to gadolinium-based contrast, sedation or anesthesia associated with increased use of contrast-enhanced magnetic resonance imaging (MRI). Dillman and colleagues also noted the possibility of increased health-care costs due to increased office visits and thyroid testing as well as the potential for delayed diagnosis due to concerns over CT use.

In light of the research cited by the FDA, Dillman and colleagues say the risk of hypothyroidism is “quite low” for children under the age of three months and “minimal to absent” for those children older than three months of age.

“On the basis of the existing literature, we believe that the decision to perform thyroid function testing after intravascular contrast material exposure should be made on a patient-by-patient basis after review of each patient’s specific risk factors,” maintained Dillman and colleagues. “Universal testing in all young children is not warranted or supported by the literature at this time.”