Utilization of cardiac stress tests with imaging has been rising over the past 20 years, with more than one-third of such tests likely to be inappropriate, according to a study published in the Oct. 7 issue of Annals of Internal Medicine. These inappropriate tests were associated with annual costs of more than $500 million.

Joseph Ladapo, MD, PhD, assistant professor in the Departments of Medicine and Population Health at NYU Langone Medical Center in New York City, and colleagues sought to track U.S. trends in cardiac stress testing with imaging, then look at the underlying factors in physician decision making. They also wanted to evaluate whether racial or ethnic disparities exist.

To this end, the authors utilized data from the National Ambulatory Medical Care Survey and National Hospital Ambulatory Medical Care Survey from 1993 to 2010. All patients included in the study were adults without coronary heart disease referred for cardiac stress tests.

Results showed that between the time periods of 1993-1995 and 2008-2010, the annual number of ambulatory visits in the U.S. in which a cardiac stress test was ordered or performed increased by more than 50 percent. Moreover, cardiac stress tests with imaging made up a growing proportion of these tests, with 59 percent of tests involving imaging in 1993-1995 compared with 87 percent in 2008-2010.

At least 34.6 percent of these tests were likely inappropriate, according to Ladapo and colleagues. This amounts to $501 million in annual costs, along with harms stemming from radiation-related cancer. “We estimate that about 500 people get cancer each year in the U.S. from radiation received during a cardiac stress test when, in fact, they most probably didn’t need any radiological imaging in the first place,” said Ladapo in a press release.

While population and provider characteristics contributed to the national growth in cardiac stress testing, the use of imaging cannot be attributed to these factors, wrote the authors. They suggested clinical decision support could reduce unnecessary cardiac stress testing, and that regular exercise treadmill tests or stress testing with ultrasound should be used as opposed to CT imaging.

The study also showed that racial or ethnic health disparities were not widespread. Black patients did not have evidence of a lower likelihood to receive a cardiac stress test with imaging compared with white patients (odds ratio: 0.91), though there was modest evidence of disparity in Hispanic patients (odds ratio: 0.75).

“Cardiac stress testing is an important clinical tool,” said Ladapo, “but we are overusing imaging for reasons unrelated to clinical need. This is causing preventable harm and increasing healthcare costs.”