A study of six large integrated healthcare systems has shown a substantial increase in the use of advanced diagnostic imaging since the mid-1990s, not just among the fee-for-service insured populations but even in HMOs, according to research published June 12 in the Journal of the American Medical Association .
“The use of diagnostic imaging in the Medicare population has increased significantly over the last two decades, particularly using expensive new technologies," such as CT, MRI and PET, wrote lead author Rebecca Smith-Bindman, MD, of the University of California, San Francisco, and colleagues. “The development and improvement in these advanced diagnostic imaging technologies is widely credited with leading to earlier and more accurate diagnoses of disease using noninvasive techniques.”
While previous studies have evaluated imaging patterns among insurance claims for fee-for-service insured populations, where the authors note financial incentives encourage imaging, no large, multisite studies had yet assessed imaging trends in integrated healthcare delivery systems.
"You would have imagined that the rate of increase would be lower," Smith-Bindman said in a release. "Our results showed very similar growth in imaging within these integrated settings as has been shown outside of these settings."
The study consisted of an analysis of electronic records for members of six large integrated health systems from different regions of the U.S. Between one million and two million patients were included each year from 1996 to 2010. In total, patients received 30.9 million imaging exams during the study period, which resulted in an average of 1.18 tests per person per year, 35 percent involving advanced imaging such as CT, MRI or nuclear medicine.
Looking past the totals to the trends, the results showed an approximate tripling of the use of CT and nearly a quadrupling of the use of MRI. In 1996, 52 out of 1,000 enrollees underwent CT, by 2010, that number had risen to 149 out of 1,000. MRI use grew from 17 in 1,000 enrollees to 65 in 1,000 over the same period. Ultrasound use approximately doubled and use of radiography increased 1.2 percent per year.
Nuclear medicine rates decreased, with a 3 percent annual decline over the course of the study, but after 2004, the authors pointed out that PET imaging rates increased from 0.24 per 1,000 enrollees to 3.6 per 1,000 enrollees, a 57 percent annual growth rate.
The data also allowed for an estimation of radiation exposure from selected tests. Utilization of CT was associated with an increase in estimated exposure, with a jump in average per capita effective dose from 1.2 mSv in 1996 to 2.3 mSv in 2010. The percent of enrollees who received high (more than 20 to 30 mSv) or very high (more than 50 mSv) radiation exposure during a given year also approximately doubled during the study period.
"It's not just that we're doing more advanced imaging tests, but we are also doing these tests in such a way that the tests deliver higher–and more variable–doses of radiation," Smith-Bindman said. "I am concerned that physicians have lowered their threshold for advanced imaging so much that it is now used even when they may not believe it is necessary or will really change their management of the patient."
Enormous variation existed from system to system, with some types of imaging being done five to 10 times more often in one system compared with the others.
The authors noted that increases in imaging were likely driven by a number of factors—improvements in technology, patient- and physician-generated demand, defensive medical practices and medical uncertainty.
“The increase in use of advanced diagnostic imaging has almost certainly contributed to both improved patient care processes and outcomes, but there are remarkably few data to quantify the benefits of imaging,” wrote the authors. “Given the high costs of imaging—estimated at $100 billion annually—and the potential risks of cancer and other harms, these benefits should be quantified and evidence-based guidelines for using imaging should be developed that clearly balance benefits against financial costs and health risk.”