A review of the appropriateness of outpatient abdominal and pelvic CT and MRI exams conducted by researchers at NYU Langone Medical Center in New York City found that most exams with relevant American College of Radiology Appropriateness Criteria were appropriate and were more likely to lead to a significant result.

However, the retrospective review also found that a large percentage of exams had no matching appropriateness criteria variant that applied, highlighting the need for more dynamic evolution of the criteria, according to Andrew B. Rosenkrantz, MD, MPA, of the Department of Radiology at NYU Langone Medical Center, and colleagues.

The findings were published online October 14 in Academic Radiology.

Rosenkrantz and colleagues were particularly interested in evaluating appropriateness criteria given the recently passed “Protecting Access to Medicare Act of 2014,” which requires providers to consult appropriateness criteria when ordering imaging services. The ACR criteria, which currently cover 197 clinical conditions with more than 900 variants, is expected to a be a primary set of guidelines to fulfill this requirement.

The authors reviewed a total of 304 abdominopelvic CT and 266 MRI studies performed over the course of one month. Only those with available documentation of the clinical encounter generating the imaging order were included.

Results showed that of the exams that had a matching variant to measure appropriateness against, 92 percent of the exams were appropriate (96 percent for CT and 86 percent for MRI). “This high fraction is particularly noteworthy given the absence of any formal clinical decision support to guide imaging orders at our institution at the time of this study,” wrote the authors.

Appropriate exams provided a significant result in 48 percent of cases compared with 24 percent of inappropriate studies. “Examinations that were not appropriate were associated with a variety of preferred alternative approaches,” explained Rosenkrantz and colleagues. “Frequently, either ultrasound or no imaging at all was appropriate, rather than the requested CT or MRI, consistent with the guidelines' aim of avoiding excess cost and unnecessary advanced imaging.”

Despite the fact that most exams with relevant criteria were indeed appropriate, the authors were highly concerned that a majority of cases did not have a relevant variant listed in the appropriateness criteria. Only 45 percent of cases (52 percent for CT and 38 percent for MRI) had a matching criteria variant. The most common indications without matching criteria were colon cancer follow up and melanoma follow up for CT, and hepatocellular carcinoma screening and elevated prostate-specific antigen without prior biopsy for MRI.

Rosenkrantz and colleagues noted that this low frequency of relevant criteria could undermine the impact of the law requiring use of such criteria. “[F]or the legislation to achieve its intended effect of generating more effective and standardized ordering of imaging on a national basis, the ACR [Appropriateness Criteria] will need to be greatly expanded to substantially lower the fraction of exempt requests.”