Non-invasive coronary CT angiography (CCTA) is a cost-effective alternative to invasive cardiac catheterization in the care of patients who have positive stress test results, but less than a 50 percent chance of having coronary artery disease (CAD), according to a study in the May issue of the American Journal of Roentgenology.
In the study, Ethan Halpern, MD, from the department of radiology at Thomas Jefferson University in Philadelphia, and colleagues compared false-negative rates, false-positive rates, costs and radiation exposure of patients for cardiac catheterization with the values associated with initial referral for CCTA.
According to the authors, costs were computed as a combination of professional and technical fees. Professional fees for CCTA and diagnostic cardiac catheterization and technical fees for CTA were obtained from the 2009 physician Medicare fee schedule provided by the Centers for Medicare & Medicaid Services.
The authors found that performing CCTA before triage to cardiac catheterization reduces overall diagnostic costs as long as the prevalence of disease is less than 85 percent. At a 50 percent prevalence of CAD, they found that performing CCTA before cardiac catheterization results in an average cost saving of $789 per patient with a false-negative rate of 2.5 percent and average additional radiation exposure of 1-2 mSv, which is minimal. The cost savings increase more than $1,000 at a CAD prevalence less than 40 percent.
“Sensitivity analysis showed that even with lower specificity, initial use of CCTA reduces overall diagnostic costs as long as the prevalence of disease is less than 75 percent,” the authors wrote.
Regarding radiation dose, the authors found with an assumption of a mean effective dose of 7 mSv for diagnostic cardiac catherization, effective radiation exposure is reduced when coronary CTA is performed with prospective ECG gating as long as the prevalence of disease is less than 30 percent. When CAD prevalence increases to 50 percent, effective radiation exposure increases 1.1 mSv, from 7 mSv to 8.1 mSv.
“Sensitivity analysis showed that at a disease prevalence up to 40 percent, the effective dose can be reduced by initial performance of CCTA provided the specificity is kept to 90 percent,” the authors wrote. “ Even when specificity decreases to a value as low as 64 percent, starting with CCTA increases the effective radiation dose only 1.5 mSv, from 7 to 8.5 mSv, at a disease prevalence of 40 percent.”
“According to our results,” Halpern said, “when a patient with an expected CAD prevalence less than 85 percent is found to have a positive stress test result, CCTA is a less expensive alternative to direct performance of cardiac catheterization.”
“Recent studies have demonstrated that diagnostic cardiac catheterization of patients with atypical symptoms will reveal significant CAD less than half of the time,” he added. “If the pretest probability of CAD is low the CCTA findings are more likely to obviate cardiac catheterization and thereby reduce both the cost and effective radiation dose of the workup.”