Clearer picture: Study finds CT scans in the ED have significant impact on diagnosis

CT scans in the ED often lead to key changes in clinical decisionmaking for symptoms commonly seen in ED visits, according to a study published in Radiology. 

Researchers from the Massachusetts General Hospital (MGH) Institute for Technology Assessment reviewed the actions of physicians in the EDs of four major academic medical centers. 

“Emergency department physicians who face increasing pressure to make clinical decisions quickly are sometimes criticized for ordering too many CT scans that may not be clinically justified,” said Pari Pandharipande, MD, MPH, director of the MGH Institute of Technology Assessment, who led the study. “We found that--for patients with abdominal pain, chest pain or shortness of breath, or with headache--physicians’ leading diagnoses and management decisions frequently changed after CT and that diagnostic uncertainty felt by physicians was alleviated.” 

Utilization of CT scanning in EDs has more than tripled in the past 20 years, the authors noted, but the benefits of that increase are unclear. A 2011 MGH study found that ED CT scans changed the diagnosis and management plans of more than 40 percent of nearly 600 ED patients with abdominal pain. That study focused on treatment of a single symptom at just one institution, so the current study was designed to take a broader look at the question. 

The study was conducted at four academic medical centers and covered periods of 15 months between July 2012 and January 2014. Participating ED physicians evaluated patients with abdominal pain, chest pain/shortness of breath or headache and were asked to complete brief surveys after their initial evaluation of the patients and again after receiving CT scan results. Pre-CT surveys asked for their initial diagnosis, their confidence in that diagnosis, any alternative diagnoses that should be ruled out and their current management decisions. Post-CT surveys asked whether the initial diagnosis had changed, whether the CT scan had helped to confirm or rule out alternative diagnoses, and whether management decisions had changed. 

In total, 245 physicians completed both pre- and post-CT surveys for 1,280 patients. After CT, physicians’ leading diagnoses changed for 51 percent of patients with abdominal pain, 42 percent of patients with chest pain/shortness of breath and 24 percent of patients with headache. The CT scan helped to confirm or rule out alternative diagnoses 95 to 97 percent of the time, across all symptom groups. Decisions about admitting patients to the hospital were changed 19 to 25 percent of the time.

“Our evaluation of physicians’ diagnostic confidence revealed compelling results,” said Pandharipande, in a release. “While there was a wide spectrum of diagnostic confidence before CT, the greater a physician’s initial confidence in a diagnosis, the less likely that diagnosis was to change after CT, indicating that physicians were sound judges of their own diagnostic certainty. But even in instances where physicians’ pre-CT confidence in their initial diagnosis was greater than 90 percent, there were still changes in from 4 to 21 percent of cases.”  

The study did not address the costs and risks, such as radiation exposures, that should be included in a full risk/benefit evaluation. But, the size and consistency of the benefits observed in this study indicate that policies solely designed to reduce the use of ED CT scans could compromise patient care. Future research should focus on better methods of identifying patients less likely to benefit from CT scanning without reducing CT use in patients who would benefit, according to the authors.