Economic Outcomes With Anatomical Versus Functional Diagnostic Testing for Coronary Artery Disease

Abstract

Background: PROMISE (PROspective Multicenter Imaging Study for Evaluation of Chest Pain) found that initial use of at least 64-slice multidetector computed tomography angiography (CTA) versus functional diagnostic testing strategies did not improve clinical outcomes in stable symptomatic patients with suspected coronary artery disease (CAD) requiring noninvasive testing.

Objective: To conduct an economic analysis for PROMISE (a major secondary aim of the study).

Design: Prospective economic study from the U.S. perspective. Comparisons were made according to the intention-to-treat principle, and CIs were calculated using bootstrap methods. (ClinicalTrials.gov: NCT01174550).

Setting: 190 U.S. centers.

Patients: 9649 U.S. patients enrolled in PROMISE between July 2010 and September 2013. Median follow-up was 25 months.

Measurements: Technical costs of the initial (outpatient) testing strategy were estimated from Premier Research Database data. Hospital-based costs were estimated using hospital bills and Medicare cost-charge ratios. Physician fees were taken from the Medicare Physician Fee Schedule. Costs were expressed in 2014 U.S. dollars, discounted at 3% annually, and estimated out to 3 years using inverse probability weighting methods.

Results: The mean initial testing costs were $174 for exercise electrocardiography; $404 for CTA; $501 to $514 for pharmacologic and exercise stress echocardiography, respectively; and $946 to $1132 for exercise and pharmacologic stress nuclear testing, respectively. Mean costs at 90 days were $2494 for the CTA strategy versus $2240 for the functional strategy (mean difference, $254 [95% CI, -$634 to $906]). The difference was associated with more revascularizations and catheterizations (4.25 per 100 patients) with CTA use. After 90 days, the mean cost difference between the groups out to 3 years remained small.

Limitation: Cost weights for test strategies were obtained from sources outside PROMISE.

Conclusion: Computed tomography angiography and functional diagnostic testing strategies in patients with suspected CAD have similar costs through 3 years of follow-up.

Primary funding source: National Heart, Lung, and Blood Institute.

Figure 1

Cumulative Total Costs by Randomized Assignment. Cumulative total costs by randomized assignment (panel A) and mean cost differences with 95% confidence intervals (panel B).

Figure 2

Mean Cost Differences by Cost Categories. Mean cost differences by cost categories A) baseline to 3 months, B) 4 months to 12 months, C) 13 months to 24 months, and D) 25 months to 36 months. Above 0 means more cost for CTA and below 0 means more cost for functional testing. Cath=cardiac catheterization; revasc=revascularization; CV=cardiovascular

Figure 3

Two-year Cost Threshold Differences from Bootstrap Analysis. The curve shows the cumulative distribution function of the mean cost difference (CTA − functional testing) from 1000 bootstrap replications out to 24 months. A cost difference ≤ $500 was seen in 58.6% of samples, a difference ≤$750 in 79.7% of samples, and ≤$1000 in 93.4% of samples.

Figure 4

Three-year Costs in Subgroups. Forest plot for mean differences and 95% confidence interval of CTA minus functional testing 3-year costs in prespecified subgroups. ECG=electrocardiogram, Echo=echocardiogram, CAD=coronary artery disease