CTA Both Clinically, Economically Comparable to Functional Testing for Suspected CAD

An economic substudy of data from the PROMISE trial indicates similar costs related to the use of CT angiography (CTA) and functional diagnostic testing strategies to evaluate nonacute chest pain in symptomatic patients. Evaluating out to 90 days of follow-up, there was only a $254 higher cost associated with the use of CTA, and from 90 days to 1 year, the average difference in cost between the two procedures remained small.

These results, published in Annals of Internal Medicine, are the latest from PROMISE (Prospective Multicenter Imaging Study for Evaluation of Chest Pain). Details of the trial’s main analysis were presented at the American College of Cardiology/i2 Scientific Session in March 2015 and showed that CTA does not yield improved clinical outcomes compared with functional testing.

“For patients similar to those studied in the PROMISE trial, with low-to-intermediate pretest probability and atypical chest pain, the results provide reassurance that CTA is comparable—from an economic and clinical point of view—to functional testing,” Jacqueline Shreibati, MD (Stanford University School of Medicine, Stanford, CA), who was not involved in the study, told TCTMD in an e-mail.

But, Shreibati added, “The trial did not answer the question of whether or not to use CTA versus functional testing in other types of patients, nor did it answer whether any testing makes a difference in outcomes.”

These opinions were echoed in an editorial accompanying the study by Joe X. Xie, MD, and Leslee J. Shaw, PhD (Emory University School of Medicine, Atlanta, GA). “The study by Mark and colleagues provides us with tremendous insight into the cost implications of diagnostic strategies for suspected CAD,” they write. “Yet, our knowledge remains limited, and future funding is required to prioritize the development of novel, efficient, and effective diagnostic approaches for suspected CAD.”

Testing Costs

For the economic substudy, researchers led by Daniel B. Mark, MD, MPH (Duke Clinical Research Institute, Durham, NC), included the 9,649 patients enrolled in PROMISE who were cared for in the fee-for-service sector of the US healthcare system. They collected information on resource use and hospital costs, conducting an intention-to-treat comparison of within-study medical costs.

At 90 days, the average cost for CTA was $2,494 compared with $2,240 for the functional testing group, a difference of $254. This disparity was driven by a higher rate of coronary revascularization (6.2% vs 3.2%) and the costs associated with it among patients who underwent CTA rather than functional testing. By the end of year 1, the mean cost difference between the two groups was $99, for a cumulative cost difference of $353 over the first year.

By year 2, the average cost difference between the two procedures had decreased to $26, and by year 3, the cost difference was $249. The researchers noted that the year 3 results were skewed by a patient in the CTA group who required, unrelated to the PROMISE trial, hospitalization for orthopedic care costing more than $300,000. When this patient was removed from the analysis, the difference in cost at year 3 was $91.

Choosing an Approach

The economic results of the PROMISE trial tell a similar story to the main results of PROMISE, according to Shreibati. PROMISE showed that the overall event rate for the composite primary endpoint of death, myocardial infarction, or hospitalization was similar between patients assigned to CTA or functional testing.

“The overall event rate was low, around 3%. In the short term, within 90 days, however, more CTA patients underwent cardiac catheterization (12.2% versus 8.1%) and revascularization (6.2% versus 3.2%),” Shreibati explained.

Looking at the economic results, CTA and functional stress testing had similar overall costs in the long term. The initial cost of a CTA was lower than functional tests, but the added expense related to catheterization and revascularization resulted in a small but nonsignificant increase in costs.

“The low event rates may in part explain why significant cost differences were not seen,” Shreibati said.

When trying to decide between an anatomical or functional testing approach, clinicians should use their understanding of a patient’s individual risk for CAD, she advised. “If a patient has low-to-intermediate risk of coronary artery disease, either CTA or functional testing can be considered,” Shreibati said. “The choice of one study over another should then be made on the basis of physician and patient preferences.”

Related Stories:

• PROMISE Analyses: Coronary CTA May Hold Some Benefits for Patients with Suspected CAD
• Coronary CTA Fails to Live Up to Its PROMISE in Suspected CAD