By Duke Medicine News and Communications

Financial reimbursement and ownership of cardiac imaging equipment appears to influence physicians’ use of cardiac stress testing, according to a new study from Duke University Medical Center.

The study finds that doctors who are reimbursed for both performing the test using their equipment and then interpreting the results were 50 to 100 percent more likely to order cardiac imaging tests on their patients than those who don’t bill the fees.

The study appears today in the Journal of the American Medical Association.

After analyzing claims from a large national insurance company, the Duke researchers found physicians who receive reimbursement for technical fees, which cover facility and equipment costs, and professional fees, which cover time spent interpreting or supervising the tests, were markedly more likely to routinely order stress imaging tests in discretionary situations when compared with physicians who are only reimbursed for professional fees or who do not bill for these procedures.

“The use of cardiac imaging technology has grown rapidly in this country and there is a lot of variation among physicians in terms of when and why they are used,” says Bimal Shah, MD, a cardiologist and assistant professor of medicine at Duke and lead author of the study.

“For the first time, we show that financial reimbursement structures may be yet another factor associated with this variation in testing behavior.”

Shah and his colleagues looked at the use of two types of cardiac stress imaging tests -- nuclear, which uses radioactive material to image blood flow, and echocardiography, which uses ultrasound images. He determined how many patients underwent routine stress testing after percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG).

In this setting, unless provoked by symptoms or a cardiac event, the American College of Cardiology guidelines recommend no early stress testing after these procedures. Despite this, Shah found that many patients still underwent stress tests and that this rate nearly doubled if the patient’s doctor billed for performing and interpreting the test.

Routine stress testing can be problematic for several reasons, according to Eric Peterson, MD, associate director of the Duke Clinical Research Institute, and the paper’s senior author. “It can expose the patients to unneeded radiation, and lead to more invasive downstream testing even when the testing likely doesn’t improve patient outcomes.”

“This study is an important first step,” says Peterson. While the findings in this study raise questions, “we need more detailed clinical data to really determine why the tests were ordered. Thus, more study is needed.” 

“Given that our medical system is already financially constrained,” says Shah, “we need to be sure that our tests are for appropriate indications and not influenced by reimbursement structures.”

Shah is a consultant to Castlight Health, manufacturer of tools that encourage transparency in health care costs.

The study was funded by United Health Care.