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Wednesday, March 23, 2011

MRI usage continues to increase

Hospital emergency departments have been ordering CT and MRI scans for an increasing percentage of injured patients without any corresponding change in the patient mix that would justify the more expensive imaging, researchers said.

In 2007, 15% of imaging in emergency departments was performed with CT or MRI for injury-related conditions, up from just 6% in 1998 (P<0.001 for trend), according to Frederick Kofi Korley, MD, of Johns Hopkins University, and colleagues.
During that a period of time, the prevalence of life-threatening conditions among emergency patients changed little, they reported in the Oct. 6 issue of the Journal of the American Medical Association.
The researchers stopped short of saying the advanced technologies were being used needlessly. But they called for a hard look at why CT or MRI is increasingly chosen in emergency departments.
"Further work is needed to understand the patient, hospital, and physician factors responsible for this increase and to optimize the risk-benefit balance of advanced radiology use," Korley and colleagues wrote.
Their conclusions were based on data from the CDC's National Hospital Ambulatory Medical Care Survey, which collects information on outpatient (including emergency department) visits at a nationwide sample of 370 nonfederal hospitals.
The data covered 5,237 emergency department visits for injury-related conditions in 1998 and 6,567 in 2007. Over this span, the proportion of visits involving life-threatening conditions increased from 1.7% to 2% (P=0.04 for trend). The fractions resulting in inpatient admission or ICU treatment did not change significantly, Korley and colleagues found.
Use of CT or MRI increased markedly over the same period, after adjusting for potential confounding variables including age, insurance status, pain severity, and the immediacy of when patients should be seen.
Korley and colleagues calculated that the odds ratio of receiving a CT or MRI scan in an emergency department in 2007 versus 1998 was 3.43 (95% CI 2.71 to 4.35).
They also identified certain factors associated significantly with greater likelihood of CT or MRI use (adjusted for confounders):
  • Severe pain, OR 1.41 (95% CI 1.21 to 1.64) versus mild pain
  • Moderate pain, OR 1.26 (95% CI 1.07 to 1.48) versus mild pain
  • Teaching hospital, OR 1.52 (95% CI 1.22 to 1.90) versus nonteaching
  • Age at least 60, OR 2.57 (95% CI 2.27 to 2.91) versus ages 18 to 45
  • Should be seen in less than 15 minutes, OR 2.06 (95% CI 1.80 to 2.36) versus should be seen in 15 to 60 minutes

Notably lacking from this list was insurance status. The odds ratio for advanced imaging for uninsured patients versus those with some form of insurance was 0.94 (95% CI 0.84 to 1.06).
The researchers also determined that, in 2008, patients undergoing CT or MRI scans remained in the emergency department far longer than patients not having such imaging.
Mean visit duration for patients having advanced imaging was 5 hours and 14 minutes (95% CI 297 to 331) compared with 3 hours and 10 minutes (95% CI 180 to 201) for other patients. But these values were not adjusted for severity of injury or other factors potentially accompanying a need for CT or MRI scans that might complicate a case.
Although Korley and colleagues had no data on the reasons for ordering CT or MRI scans rather than conventional x-rays for individual cases, they still found their findings to be worrisome.
"CT scans are more sensitive for detecting serious injuries, but monetary and nonmonetary costs are associated with their use," they wrote.
Nonmonetary costs include health risks, such as the increased radiation exposure relative to conventional x-rays as well as reactions and other adverse effects related to contrast agents. The latter are also an issue with MRI.
On the other hand, Korley and colleagues acknowledged that CT and MRI are simply better than conventional x-rays for diagnosing certain injuries, such as cervical spine fractures.
Other factors that may promote their use include fear of litigation for missed diagnoses, direct-to-consumer advertising, the increased prevalence of CT and MRI machines in or near emergency departments, and advances in the equipment that make it easier to use, the researchers indicated.
"The role of evidence-adoption strategies such as computerized decision support and audit and feedback in promoting adherence to decision rules for imaging needs to be further understood," they concluded.
They noted several limitations to the study, including the absence of detail on injury nature and severity, the lack of data on incidental findings that might have improved patients' overall outcomes, and the database's reliance on retrospective chart review.

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