On target: High diagnostic yield for chest CT follow up following abnormal x-ray

A follow-up chest CT after abnormal x-ray findings produces a high yield of relevant findings, according to a study published online in Radiology on Dec. 22.

The research team, including H. Benjamin Harvey, MD, of Massachusetts General Hospital and Harvard Medical School, found that the rate of recommendation for additional imaging has increased by 200 percent since 1995.

“Chest radiographic imaging is the most common outpatient diagnostic imaging study performed in the United States, and as many as half of all RAIs that arise from thoracic diagnostic studies are prompted by radiographic imaging of the chest,” the authors wrote. “The purpose of our study was to evaluate the diagnostic yield of recommended chest CT examinations prompted by abnormalities detected at outpatient radiographic examinations of the chest.”

For the study, more than 29,000 x-ray exams were queried to determine if a follow up CT exam of the chest was performed within one year and these CT images were reviewed to determine if an abnormality corresponding to the chest x-ray was discovered. These abnormalities were categorized as clinically relevant or not clinically relevant.

Study results showed that 4.5 percent of the outpatient chest x-ray examinations contained recommendations for a chest CT.

Of these patients, 65 percent underwent the follow up CT exam within one year and clinically relevant abnormalities were present on 41.4 percent of the CT exam results. Additionally, from the pool of follow up CT exams, 20.6 showed nonclinically relevant corresponding abnormalities and 38.1 percent showed no abnormalities.

The most common malignancy detected in the recommended CT scans was adenocarcinoma of the lung, and represented 46.6 percent of detected abnormalities.

The results also showed that older patients and former smokers were more likely to receive recommendations for additional imaging—likely due to a higher likelihood of x-ray abnormalities and a lower threshold for radiologists to recommend additional CT examinations in these patients.

Harvey and colleagues noted that the shift in healthcare to value-based payment models makes validation of radiology work vital.

“Our study demonstrates that chest CT examinations obtained within one year of [recommendations for additional imaging] are associated with a high diagnostic yield of clinically relevant findings, and one in every 13 examinations yielded a previously unknown malignancy,” Harvey and colleagues wrote.  “These findings suggest that [recommendations] for chest CT examinations prompted by outpatient chest radiographic examinations represent a valuable contribution to patient care.”