Cardiac CT angiography (CCTA) appears to be cost effective compared with SPECT imaging, and it does not result in higher downstream resource utilization, according to research led by Eddie Hulten, MD, of Walter Reed Medical Center in Washington, D.C., and shared at the Society for Cardiac Computed Tomography (SCCT) conference in July.

Public health officials have called for comparative cost-effectiveness research of CCTA and other diagnostic imaging strategies in assessing angina in low to intermediate risk patients, yet there is a dearth of studies comparing downstream resource utilization of CCTA and myocardial perfusion stress imaging.

Hulten and colleagues retrospectively reviewed 252 symptomatic patients without known coronary artery disease (CAD) who underwent CCTA between May 2006 and April 2008 and a comparison group of 241 age and gender matched symptomatic patients without known CAD who underwent myocardial perfusion SPECT imaging in the same time period.

The primary outcome was the composite utilization of clinical services for persistent symptoms despite negative imaging. Researchers factored in cardiovascular specialist referrals, ER visits, hospital admissions and cardiac testing.

Ninety percent of CCTA patients had no CAD or non-obstructive CAD compared with 94 percent of SPECT patients with no ischemia or prognostically normal results. Composite rates of downstream utilization were nearly equivalent at 23.5 percent and 24.3 percent for CCTA and SPECT, respectively, reported Hulten.

Supporting data
Hulten also summarized other published data about CCTA costs, dividing cost categories into immediate; including test costs, time to diagnosis, hospital duration, safety, patient costs and physician and staff costs; and downstream costs, which include repeat testing, additional testing and incidental findings.

A literature search identified two randomized trials, three observational studies, three theoretical mathematical models and two studies of the costs of incidental findings.

Six studies comparing SPECT and CCTA reported cost savings per patient ranging from $79 to $3,346. Three studies reported that CCTA resulted in more downstream SPECT studies while SPECT resulted in more invasive coronary angiography procedures. A fourth study found that SPECT resulted in more invasive coronary angiograms and CCTA studies. For clinical outcomes assessment, one study reported that CCTA decreased immediate hospital costs and another showed that CCTA decreased time to diagnosis and ER costs.

Incidental CCTA findings in three studies ranged from 34.6 to 43 percent, with downstream costs of incidental findings per CCTA of $15 to $86.

Hulten concluded:

• Outpatient CCTA appears cost-effective compared with SPECT;
• CCTA in the ER for possible acute coronary syndrome patients appears similarly cost-effective without a burden of increased downstream resource utilization; and
• As data accumulate, the paradigm may shift from costly “rule out MI” admissions for serial ECG/enzymes/observation to apparently safe and cost-effective “ER rule out with CCTA.”

However, Hulten cautioned that additional comparative cost-effectiveness studies are needed especially those that focus on CCTA and other modalities.