AJR: Abdominal CT often changes diagnosis

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Data provided by abdominopelvic CT of emergency department patients with nontraumatic abdominal pain changed treatment plans for almost half of patients and significantly reduced probable hospital admissions, according to a study conducted at Massachusetts General Hospital (MGH) and published in the February issue of the American Journal of Roentgenology.

Other studies have calculated the increasing use of CT in the ER, but have not assessed the benefits of CT in this setting. “This study adds the perspective of the emergency department physician and shows the difficulties that they have in appropriate evaluation and patient management,” lead author Hani Abujudeh, MD, MBA, of MGH Radiology told Health Imaging News.

“The use of CT in the ED may improve overall utilization of healthcare system resources,” offered Abujudeh. That’s because CT impacted management decisions for 42 percent of patients in the study, potentially preventing inappropriate overuse of hospital resources and saving downstream dollars.

"Our report addresses an important question with substantial policy relevance – what is the value of CT scanning in the emergency department setting?" added Scott Gazelle, MD, PhD, MPH, an MGH radiologist and director of the Institute for Technology Assessment, senior author of the study. "We specifically examined how the use of CT for patients with abdominal pain affects physicians' thinking about their patients' diagnosis, their confidence in the diagnosis and the treatment plan; and we found that it significantly affected all three."

Given the increasing scrutiny of CT costs, the researchers sought to define its usefulness and effectiveness for individual patient management. "We've strongly believed that the use of CT in the emergency department can improve efficiency in the workup for many conditions, but we haven't had the evidence we would like to back up that assertion,” explained Gazelle.

Previous studies have demonstrated the impact of CT in altering diagnoses and treatment plans. However, most of the studies were retrospective, provided minimal generalizability or focused on a relatively small patient population.

The MGH team focused on abdominal CT because abdominal pain is a fairly common chief complaint among ED patients. Clearly defined diagnostic guidelines are lacking, exacerbating the diagnostic challenge.

The researchers designed a prospective study based on pre- and post-CT questionnaires assessing most likely diagnoses, level of certainty and intended patient management plans. The study enrolled 584 adults presenting to the ED with nontraumatic abdominal pain between Nov. 12, 2006 and Feb. 26, 2008.

“The use of CT altered the leading diagnoses in 48.6 percent of cases,” reported Abujudeh and colleagues. The researchers calculated a 126 percent decrease in the diagnosis of no acute condition after CT. The five most common pre-CT diagnoses were renal colic, intestinal obstruction, no acute condition, appendicitis and diverticulitis, in order of decreasing frequency. The order switched to no acute condition, renal colic, intestinal obstruction, abscess and appendicitis post-CT.

CT significantly increased diagnostic certainty. The authors found a mean change in certainty of 21.7 percent in cases in which the diagnostic category did not change and 34.9 percent in cases in which the diagnostic category did change.

Finally, the study showed that CT changed the management plan in 42 percent of patients. “For example, the use of CT reduced the number of patients for whom observation was planned by 44 percent … and increased the number of patients discharged from the hospital by 55 percent … Of the 440 patients for whom hospital admissions were planned before CT, 24.1 were discharged after CT. Of the 142 patients for whom discharge was planned before CT, 20.4 percent were admitted after CT. Overall, the use of CT reduced planned admissions by 17.5 percent,” according to the authors.

"Poor diagnostic certainty can lead to poor decision making,” explained Abujudeh. “Decisions made without the benefit of CT may not be best for patients.”

The authors noted several reasons CT influences triage among this patient population. For starters, clinical examinations offer limited diagnostic accuracy for some abdominal conditions. In contrast, abdominal CT provides accurate diagnosis of common acute abdominal conditions and can exclude surgical abdominal conditions.

The current study supports previous studies validating the use of abdominal CT in various acute conditions and demonstrating its influence on disposition and resource utilization, and it bolsters existing knowledge by incorporating various diseases processes, boosting generalizability of the findings. However, the descriptive study did not incorporate a control group nor did researchers gather data about the role of other diagnostic tests.

While the study did not evaluate economic data, the authors wrote, “the increased utilization of each CT unit in recent decades has brought about a lower technical cost per examination and decreased cost-benefit ratio.” They suggested that quantifying cost savings and resource utilization rates requires further investigation.

"While we didn't include a cost analysis in our study, it is fair to say that our results suggest the CT scan might reduce the use of other tests and procedures and therefore lower overall costs. Another benefit is that CT provides rapid results, which makes the workup process more efficient and can reduce both monetary costs and the time required to move patients through the ED," Abujudeh noted.