Which tests are of concern for shellfish allergy due to potential contrast agents?

• A. Ultrasound
• B. Tests with contrast agents such as CT with contrast or MRI with contrast
• C. X-ray
• D. EKG

Answer: (B)

The key idea is that allergy concerns in this context come from imaging tests that use contrast dyes. CT with contrast and MRI with contrast involve iodinated or gadolinium-based agents, which can provoke allergic reactions in some people, so those tests are the ones to watch for in someone with a shellfish allergy. Ultrasound, standard X-ray, and EKG typically don’t use these contrast agents, so they don’t carry the same contrast-related allergy risk. If there’s a known history of contrast reaction, clinicians may premedicate or choose non-contrast imaging or alternative tests.