Cost-effectiveness of screening for asymptomatic carotid stenosis

Purpose: The benefit of carotid endarterectomy for patients who are asymptomatic with >60% carotid stenosis has been established by the Asymptomatic Carotid Atherosclerosis Study (ACAS). Which screening strategy is most appropriate is still unclear. This study assessed the cost- effectiveness of ultrasound screening for asymptomatic carotid stenosis. Methods: Cost-effectiveness analysis was performed with a Markov model and with data from ACAS and other studies. Results: For 60-year-old patients with a 5% prevalence of 60% to 99% asymptomatic stenosis, duplex ultrasound screening increased average quality-adjusted life years (QALY; 11.485 vs 11.473) and lifetime cost of care ($5500 vs $5012) under base-case assumptions. The incremental cost per QALY gained (cost-effectiveness ratio) was $39,495. Screening was cost-effective with the following conditions: disease prevalence was 4.5% or more, the specificity of the screening test (ultrasound) was 91% or more, the stroke rate of patients who were medically treated was 3.3% or more, the relative risk reduction of surgery was 37% or more, the stroke rate associated with surgery was 160% or less than that of the North American Symptomatic Carotid Endarterectomy Trial or ACAS perioperative complication rates, and the cost of ultrasound screening was $300 or less. A one-time screening, compared with a screening every 5 years, had more QALY (11.485 vs 11.482) and lower cost ($5500 vs $5790). Screening without arteriography, compared with screening with arteriographic verification, provided few additional QALYs (11.486 vs 11.485) at additional cost ($6896 vs $5500). The cost-effectiveness ratio was sensitive to assumptions about the stroke rate of patients who were asymptomatic and other variables. Conclusions: Screening for asymptomatic carotid stenosis can be cost-effective when both screening and carotid endarterectomy are performed in centers of excellence.