Medicare patients who underwent coronary CT angiography (CCTA) for an initial diagnostic evaluation of suspected coronary artery disease (CAD) were more likely to undergo subsequent invasive procedures and accrue more costs than patients given stress tests, researchers reported in the Nov. 16 issue of the Journal of the American Medical Association.

Jacqueline B. Shreibati, MD, of the Stanford School of Medicine in Stanford, Calif., and colleagues noted that as a diagnostic test, CCTA has been shown to be highly sensitive in detecting coronary stenosis compared with coronary angiography, with the advantage of being noninvasive. They speculated that CCTA might lower spending on follow-up tests if findings ruled out significant CAD.

But CCTA has moderate specificity. Alternatively, the authors argued, CCTA might increase costs if anatomic information on atherosclerotic plaques was inconclusive or positive, leading to more tests and procedures. By comparing CCTA to stress testing on Medicare patients evaluated for CAD in an outpatient setting, they aimed to determine utilization and expenditures.

For the retrospective, observational cohort study, Shreibati and colleagues obtained a 20 percent random sample of Medicare fee-for-service beneficiaries who received noninvasive testing for CAD in an outpatient setting between 2005 and 2008. Patients with prior CAD, who had undergone a prior test, were younger than 66, were in a health maintenance organization or who had an invalid referral were excluded, leaving a cohort of 282,830 patients. The follow-up period was 180 days after the index test.

The analysis found that myocardial perfusion scintigraphy (MPS) was used most frequently (in 46.8 percent of the patients); stress echocardiography came in second (28.5 percent); exercise electrocardiography third (21.6 percent); and CCTA last (3.1 percent).

Patients who underwent CCTA had more additional noninvasive tests compared with MPS (5 percent vs. 3.2 percent); were more likely to have subsequent cardiac catheterization (22.9 percent vs. 12.1 percent); have percutaneous coronary intervention (7.8 percent vs. 3.4 percent); and coronary artery bypass graft surgery (3.7 percent vs. 1.3 percent).

Cost analyses showed that mean total spending and CAD-related spending was higher in the CCTA group compared with MPS. Total spending for CCTA was $4,200 higher than MPS, and CAD-related spending was almost 40 percent higher for patients who underwent CCTA. The researchers attributed much of the cost difference to the increased use of invasive coronary procedures.

"This study documents that patients who undergo CCTA frequently undergo additional cardiac testing, particularly cardiac catheterization, and subsequent coronary revascularization with PCI or CABG surgery, the authors wrote. Our results are consistent with the view that findings from CCTA, compared with those from stress tests, can more frequently trigger the cascade of further testing culminating in revascularization.

They added that they did not track follow-up beyond 180 days and thus could not assess subsequent cardiac events, including possible improvement in survival among the CCTA group. Claims data provided no insights on symptoms or quality of life. The use of Medicare claims and an outpatient setting might not make results representative for patients in other health plans or other care settings, they pointed out.

Shreibati and colleagues concluded that although CCTA made up a small slice of diagnostic testing, its use may grow. Our data suggest that increased use of CCTA may greatly increase subsequent diagnostic testing and invasive cardiac procedures, they warned. The increased use of invasive procedures and the higher spending on care after CCTA documented in this study suggest that clinicians and policy makers should critically evaluate the use of CCTA in clinical practice, based on studies of subsequent outcomes.