Use of diagnostic imaging tests in the United States has increased across the board in recent years, with more patients getting the tests and more tests being ordered per patient, researchers said on Monday.
Their 10-year study of patients in a large managed care plan showed an advanced type of X-ray called computed tomography or CT scans doubled, and magnetic resonance imaging or MRI scans per patient tripled.
"There was really a profound increase," said Dr. Rebecca Smith-Bindman of the University of California, San Francisco, whose research appears in the journal Health Affairs.
The findings reinforce several studies, including one in July by the Government Accountability Office that found Medicare spending on medical imaging doubled to about $14 billion a year between 2000 and 2006, driven largely by increases in high-tech imaging.
Other studies have found similar increases. Smith-Bindman's team wanted to see what factors were driving those increases, and whether there might be obvious areas for cuts.
"The patterns of increase were consistent among every group and every disease that we looked at, which makes it a little tricky to figure out how we can target one group or one disease to decrease imaging," Smith-Bindman said in a telephone interview. "It's really across the board."
For the study, the researchers analyzed data from 377,000 patients enrolled in the Group Health Cooperative health maintenance organization in Washington state between 1997 and 2006, who had a total of 5 million diagnostic tests.
They found increases in all types of imaging, with the average cost per patient per year almost doubling during the study period to $443 from $229.
Ultrasound use rose 5 percent per year, CT scans rose by 14 percent a year and MRIs rose by 26 percent per year, while use of conventional X-rays — which made up the bulk of the tests — was about flat, Smith-Bindman said.
When they looked to see if particular diseases were driving the increases, nothing really stood out.
"It's increasing everywhere the same," Smith-Bindman said. "That would suggest it's not patient symptoms that are driving the increase but a whole lot of other factors."
Instead of replacing older tests, the study found newer tests were being added on top of the old ones.
Smith-Bindman said the study illustrated the need to curb unnecessary imaging, but said it would take more research to determine which tests do the most good.
She said the benefits of imaging need to be weighed against their risks, including false positive results and the increased radiation exposure associated with CT scans.
"From my point of view, this is a real harm that needs to be balanced against the benefit of CT," Smith-Bindman said.
The study did not address whether the imaging was appropriate and whether the increase was associated with improvements in patient care, she said.