Money may not be the driving force behind increased medical imaging, according to new research that finds imaging, even when provided through HMOs which do not use a fee-for-service model, has increased significantly over the past 15 years.
“It was a little bit surprising that in a setting where you don’t have those financial incentives, imaging was going up at about the same rate,” said Dr. Rebecca Smith-Bindman, a professor of radiology and biomedical imaging at the University of California at San Francisco and an author on the study, which was published in the Journal of the American Medical Association, Tuesday.
“What’s happened is that we’ve lowered our threshold for testing so far that no one really thinks about it,” she said.
Researchers speculated that when patients weren't paying per service, diagnostic imaging might be less frequent. Instead, they found that over the years, use of tests increased at about the same rate as if they were paying per service, although there was less testing in general among HMO patients.
Use of CT scans increased from 52 per 1,000 patients in 1996, to 149 per 1,000 in 2010, raising concerns about associated radiation exposure and possible increases in cancer risk. CT scans capture cross-sectional images of the body and result in more radiation exposure than X-rays.
The study also found that many individuals received repeat testing, accumulating higher doses. By 2010, nearly 11 percent of patients who received imaging had an annual radiation exposure exceeding 20 millisieverts -- the annual allowable occupational exposure in Europe. (It is 50 mSv in the U.S.)
"While it is not appropriate to set exposure limits when radiation is required for health benefit, the number of patients exposed to such levels highlights the need to consider this potential harm when ordering imaging tests," the study says.
But experts say there is more at play than the risks of exposure, which are real but relatively small. The overuse of advanced imaging can thrust patients into a cycle of unnecessary testing that can be costly and stressful.
"It's not just radiation," said Steven Woloshin, co-director of the Center for Medicine and the Media at the Dartmouth Institute for Health Policy and Clinical Practice, who was not involved with the research.
"The harms of testing include finding stuff that doesn't matter,” he said. “You can get overdiagnosis, which may generate more scans and testing. You can get false positives that generate a lot of harm, because they can scare people."
The question about what is driving such increases, especially if it isn't money, remains.
"The technology really is remarkable, so that may be a big part of it," Smith-Bindman said, stressing that imaging can help detect problems and save lives. "But not all the drivers are necessarily good. Everyone is so enamored of imaging. Patients want it, doctors want it -- there's a really strong demand."
She and her co-authors also said fear of malpractice suits may play a role.
There are some efforts to address concerns. Both Smith-Bindman and Wolshoim pointed to the “Choosing Wisely" campaign, which tasks major medical specialty organizations to list aspects of their specialties that physicians and patients should question to spark conversation about the necessity of various tests and treatment.
The American College of Radiology, for example, has called for a stop in imaging among patients with uncomplicated headaches.
But the continued climb of medical imaging even in HMOs suggests that much of the onus is on patients to try and understand the relative risks and benefits and discuss them with their doctors.
"It's really hard to do, especially if you're sick, but the questions are, 'Do I really need this test?'" Wolshoim explained. "Sometimes the answer is 'yes' and we don't want to scare people about the possible risks. But raising the issue with the doctor may be useful. A lot of time, they expect there's patient demand."