Significant discrepancies in emergency department (ED) neuroimaging according to patient and hospital demographics underscore the need for more sound imaging guidelines and greater attention to imaging overuse by ED physicians, not just radiologists, according to research published Feb. 14 in the Archives of Internal Medicine.

Neuroimaging accounts for the greatest increase in CT and MRI use in U.S. EDs, with recent research suggesting that up to 4,000 future cancers may result from head CTs performed in 2007 alone, according to Ali S. Raja, MD, MBA, of the department of emergency medicine at Brigham and Women’s Hospital in Boston, and co-authors. Despite these concerns and heightened scrutiny of imaging overuse, no national benchmarks for ED neuroimaging are available for hospitals to evaluate volume and appropriateness.

In a research letter, the authors calculated head CT and MRI use in U.S. EDs, pulling data from the 2007 National Hospital Ambulatory Medical Care Survey (NHAMCS).

Based on the NHAMCS sample of 35,490 ED visits, Raja and colleagues estimated 117 million visits to 4,891 U.S. EDs in 2007. Head CTs were performed in 6.7 percent of visits and head MRIs in 0.26 percent. The leading reasons for head CTs included trauma (18 percent), headache (13 percent) and dizziness (6 percent).

Increasing age was the strongest predictor of head CT, with one in 34 children and one in seven patients 65 and older undergoing scans. “Current guidelines addressing the use of ED head CT for trauma and acute headache exclude these older patients,” the authors pointed out. “Organizations interested in measuring and reducing neuroimaging will be challenged to define acceptable evidence-based appropriateness standards for older adults.”

Raja and colleagues also found that rural hospitals and facilities owned by state or local governments (as opposed to nonprofit hospitals) were associated with lower CT administration.

Non-Hispanic blacks were significantly less likely to undergo CT, with one in 19 non-Hispanic blacks receiving CTs and one in 14 non-Hispanic whites undergoing the procedure. “[I]t remains unclear whether this difference represents a quality disparity (i.e., underuse) or an overuse disparity because the optimal rate of imaging is unknown and we could not assess appropriateness,” the authors acknowledged.

An accompanying commentary applauded the researchers’ attempt to establish national ED neuroimaging baselines, citing a Canadian study that revealed neuroimaging disparities for minor head trauma by as much as 16 to 70 percent between hospitals and 6 to 80 percent among individual physicians. “Understanding these variations is a key step to determine appropriate use,” wrote the commentary’s authors Jeffrey A. Tabas, MD, and Renee Y. Hsia, MD, MSc, of the department of emergency medicine at the University of California, San Francisco, School of Medicine.

“[T]his study provides a valuable benchmark for national neuroimaging rates,” Tabas and Hsia continued. “What this report cannot answer, however, is whether our current imaging rates are too low (resulting in significant amounts of inappropriately missed disease), just right or too high (resulting in excessive risks from imaging without significant improvements in outcomes).”

Indeed, according to Raja et al, their study was the first nationally representative sample of ED neuroimaging in the U.S. The commentary’s authors reiterated the importance of this lack of information, identifying it as part of systematically ill-understood trends and undefined guidelines for neuroimaging. “[W]hat is the desired outcome?” asked Tabas and Hsia. “Should our goal be the detection of any 'radiologically significant' injury…Or should it be detection of only those injuries requiring neurosurgical intervention…How much specificity is it worth sacrificing to increase our sensitivity for radiologically significant injury?”

These questions get at the underlying, two-fold importance of neuroimaging standards for the ED—the guidelines are pipelines to diagnostic outcomes and they are the groundwork for imaging utilization—use and overuse—of neuroimaging. And in the ED, where the ionizing radiation of CT is a corollary of this highly common modality, patient outcomes must be seen as a balance between adequately and overly sensitive imaging guidelines. “To achieve the best interests of our patients, we must be led by our heads, not by our technology,” concluded Tabas and Hsia.