Purpose: To evaluate the relative cost-effectiveness of six non-invasive cardiac imaging tests in stable outpatients with suspected coronary artery disease (CAD) including: 1) stress echocardiography (Echo), 2) stress Echo with contrast agent (Echo+Contrast), 3) stress Echo with contrast agent used only if initial results are not interpretable (Echo>Contrast), 4) 64-slice computer tomography angiography (CTA), 5) cardiac magnetic resonance imaging (CMRI), and 6) stress single-photon emission computed tomography (SPECT).
Method: A decision-analytic Markov model was constructed to simulate the costs and consequences of diagnostic testing in a hypothetical cohort of patients presenting with chest pain in an ambulatory setting, with an intermediate risk of CAD after clinical evaluation. Resource use and costs were derived from Ontario data sources, including the Ontario Health Insurance Plan Schedule of Benefits and Ontario Case Costing Initiative. Estimates of diagnostic test characteristics (sensitivity, specificity) were identified by systematic review and statistically pooled using a bivariate regression approach. Data sources for other model parameters were published data identified by systematic review. The analysis took the perspective the Ontario public health care system and was conducted over a lifetime time horizon. Costs were expressed in 2008-2009 Canadian prices. The primary outcome was quality-adjusted life years (QALYs). Costs and QALYs were discounted at an annual rate of 5%. Cost-effectiveness was evaluated using two conventional willingness-to-pay thresholds: $50,000 per QALY and $100,000 per QALY. Uncertainty around the results was explored with probabilistic sensitivity analysis with 10,000 simulations.
Result: Echo>Contrast was the least expensive test (expected lifetime costs of $21,536) with expected lifetime QALYs of 10.02. CTA was more slightly more expensive ($21,618) and effective (expected lifetime QALYs of 10.05) than Echo>Contrast; thus CTA was cost-effective relative to Echo>Contrast with an incremental cost-effectiveness ratio of $2,958 per QALY. CTA dominated Echo, Echo+Contrast, CMRI, and SPECT, and extendedly dominated Echo. The probability that CTA was cost-effective at a willingness-to-pay of $50,000 per QALY and $100,000 per QALY was 0.929 and 0.934, respectively. Varying individual parameter values across plausible ranges in a series of 1-way sensitivity analyses did not change the finding that CTA was cost-effectiveness.
Conclusion: Sixty-four slice computer tomography angiography appears to be a cost-effective non-invasive cardiac imaging option for intermediate risk patients with suspected CAD in an ambulatory setting.