CT: Doing more but getting less

Study finds that CT does not necessarily live up to diagnostic yield of exams. Image Source: The Internet Encylcopedia of Science

CHICAGO—Despite continuing technical advances and increased use of CT in clinical practice, the diagnostic yield of CT exams has actually decreased over the past decade, according to research conducted at Massachusetts General Hospital in Boston and presented this week at the 94th scientific assembly and annual meeting of the Radiological Society of North America (RSNA).

“The purpose of our study was to determine if the growth of CT use in clinical practice has been accompanied by a change in the diagnostic yield and recommendations in radiology reports,” said Pragya Dang, MBBS.

A Natural Language Processing program developed at the facility, Leximer, was used to analyze reports of all CT exams performed at the institution from 1996 to 2005.

“We determined finding and recommendation rates in reports of exams for different age groups, gender, single or multi-region exams, body regions scanned and number of CT exams performed,” she said. “The temporal trends for the recommendation and findings rates in the CT reports were also determined.”

In addition to univariate and bivariate statistics, analysis of covariance was performed to test the effect of patient and scan variables on findings and recommendation rates over time, Dang noted.

She reported that the group found there has been a significant growth in volume of CT exams (from 29,481 to 96,522 at the rate of 14 percent per year over the study period), which has far outpaced the increase in recommendation rates for further imaging studies in the radiologist’s report in these exams (13.6 percent to 19.6 percent, increasing by 0.5 percent per year).

“Over this time, the rate of findings in radiology reports changed from 79.5 percent to 75.4 percent, decreasing at a rate of 0.6 percent per year,” Dang said.

She noted that children had lower findings (65.5 percent) and recommendation rates (1.2 percent) than the adults’ findings (77.6 percent) and recommendation rates (18.3 percent). Finding rates were higher in patients with three or more CT exams (80.8 percent) than those who had single exams (72.9 percent). Recommendations for further imaging tests decreased in patients who had three or more CT exams, Dang reported.

“The highest findings rates were noted in extremity and chest CT and highest recommendations rates were seen in chest, 30.7 percent, and head CT, 18.3 percent,” she said.

The researchers found that from 1996 to 2005, recommendation rates increased for all radiology specialties, with the most increase occurring in chest and neuroradiology; however, finding rates decreased for all radiology sub-specialties, except neuroradiology.

“Our assessment of CT exams performed in our academic center over a 10-year period showed a rapid increase in the volume of CT exams and a small, yet significant, decrease in yield while recommendation rates increased slightly,” Dang stated.