"Collectively, these limitations might explain much of the differences in use according to physician billing status," wrote Dr. Hollenbeck and Dr. Nallamothu.
They acknowledge that the findings are "robust," but they also say that "It is uncertain whether the observed increase in imaging utilization is entirely a bad thing."
A shift from the inpatient to the outpatient setting over the last decade or so has been linked to a dramatic decline in mortality from cardiac disease, they said. Office-based imaging might improve quality of care by leading to potentially earlier diagnosis, and keeping referrals close by may also increase the coordination of care, said Dr. Hollenbeck and Nallamothu.
But they also note that cardiology has been shifting back to the hospital, and that government regulators are creating policies that will likely encourage that move. That could lead to higher costs again, they said.
"Moving forward in the current era of health care reform, the focus should be less about eliminating incentives altogether, and more about getting the price right in the first place," wrote Dr. Hollenbeck and Dr. Nallamothu.
The study was funded by United Healthcare, and one study author was a United Healthcare employee. Dr. Nallamothu reported no conflicts. Dr. Shah and Dr. Hollenbeck both received grants from the Agency for Health Care Research and Quality.