Purpose: To assess the effectiveness and cost-effectiveness of state-of-the-art noninvasive diagnostic imaging strategies in patients with a transient ischemic attack (TIA) or minor stroke who are suspected of having carotid artery stenosis (CAS).
Materials and methods: All prospectively evaluated patients provided informed consent, and the local ethics committee approved this study. Diagnostic performance, treatment, long-term events, quality of life, and costs resulting from strategies employing duplex ultrasonography (US), computed tomographic (CT) angiography, contrast material-enhanced magnetic resonance (MR) angiography, and combinations of these modalities were modeled in a decision tree and Markov model. Data sources included a prospective diagnostic cohort study, a meta-analysis, and a review of the literature. Outcomes were costs, quality-adjusted life-years (QALYs), incremental cost-effectiveness ratios, and net health benefits (QALY-equivalents), with a willingness-to-pay threshold of euro 50,000 per QALY and a societal perspective. The strategy with the highest net health benefit was considered the most cost effective. Extensive one-way, two-way, and probabilistic sensitivity analyses to explore the effect of varying parameter values were performed. The reference case analysis assumed that patients underwent surgery 2-4 weeks after the first symptoms, and the effect of earlier intervention was explored.
Results: The reference case analysis showed that duplex US combined with CT angiography and surgery for 70%-99% stenoses was the most cost-effective strategy, with a net health benefit of 13.587 and 15.542 QALY-equivalents in men and women, respectively. In men, the CT angiography strategy with a 70%-99% cutoff yielded slightly more QALYs, at an incremental cost of euro 71,419 per QALY, compared with duplex US combined with CT angiography. In patients with a high-risk profile, in patients with a high prior probability of disease, and when patients could be treated within 2 weeks after the first symptoms, the CT angiography strategy with surgery for 50%-99% stenoses was the most cost-effective strategy.
Conclusion: In diagnosing CAS, duplex US should be the initial test, and, if its results are positive, CT angiography should be performed; patients with 70%-99% stenoses should then undergo carotid endarterectomy. In patients with a high-risk profile, a high probability of CAS, or who can undergo surgery without delay, immediate CT angiography and surgery for 50%-99% stenoses is indicated.