USING MODELING TO PROJECT OPTMIAL CAROTID STENOSIS SCREENING PRACTICES

USING MODELING TO PROJECT OPTMIAL CAROTID STENOSIS SCREENING PRACTICES

Purpose: Carotid artery stenosis (50-99% extracranial internal carotid artery blockage) is a risk factor for ischemic stroke. The United States Preventive Services Task Force (USPSTF) recently recommended against screening for asymptomatic carotid artery stenosis (ACAS) in the general population, although the USPSTF report also suggested that improved testing approaches could justify some screening. We sought to use simulation modeling to identify potentially efficient ACAS screening practices.

Methods: We developed a decision analytic model to compare the following screening strategies for ACAS in 65-year-olds in the U.S.: 1) general population screening with Duplex ultrasound (DUS); 2) focused DUS screening on individuals at highest risk for ACAS (based on clinical risk factors); 3) screening with confirmatory diagnostic test (ACAS diagnosis requires positive DUS and follow-up magnetic resonance imaging angiography results); 4) focused screening with confirmatory diagnostics (combination of strategies 2 and 3); and 5) no screening. Individuals' stroke risks were based their ACAS state. In the model, patients with positive ACAS test results undergo revascularization (carotid endarterectomy), which reduces the risk of stroke (relative risk of 0.54). ACAS prevalence (1.0%), test performance parameters (including sensitivity and specificity, ranging from 88-98%), and revascularization benefits, risks and costs, were estimated from published sources. Discounted lifetime costs and quality-adjusted life years (QALYs) were projected for each strategy.

Results: Strategy 5 (no screening) had lifetime discounted costs and QALYs of $7,758 and 11.695, respectively. All other strategies were dominated (i.e., had higher costs and lower or equal QALYs), with costs and QALYs ranging from $7,766 (strategy 4)-$9,464 (strategy 1) and 11.695 (strategies 2 and 4)-11.678 (strategy 1). Results were robust to changes in all parameters related to costs inputs, utility values, and revascularization risks and benefits in one-way sensitivity analyses. Results were sensitive to the probability of stroke in ACAS patients the specificity of the DUS test for ACAS (Figure).

Conclusions: The USPSTF recommendation is consistent with our cost-effectiveness results for general population or staged screening for ACAS, although identifying ACAS patients at higher risk for stroke (i.e., risk stratification among ACAS patients) coupled with improved DUS specificity could result in cost-effective ACAS screening strategies.

 

 

 

 

 

 

 

Figure