Noninvasive Carotid Artery Testing: A Meta-analytic Review

PURPOSE: To compare the operating characteristics of six noninvasive tests for carotid artery stenosis. DATA SOURCES: A structured search was done using MEDLINE, reference lists from selected articles, and bibliographies from neurology textbooks that focused on the diagnosis of carotid artery stenosis in humans. The search yielded 568 articles. STUDY SELECTION: Articles were selected if the noninvasive test results they presented used carotid angiography as the reference standard for comparison, if carotid artery occlusion was considered as a separate category, and if contingency tables could be constructed. DATA EXTRACTION: At least two physicians reviewed all selected articles. Items abstracted included patient demographics, study design, sites of patient enrollment, whether the interpretation of test outcomes was blinded, and specific results. Sensitivity, specificity, receiver operating characteristic (ROC) curves, and summary measures of effectiveness for each test were calculated. RESULTS: Carotid duplex ultrasonography, carotid Doppler ultrasonography, and magnetic resonance angiography have sensitivities between 0.82 and 0.86, specificities at 0.98, and test-effectiveness measures at or exceeding 3.0 when predicting 100% occlusion. For carotid stenosis of 70% or more, these three tests and supraorbital Doppler ultrasonography all have sensitivities of 0.83 to 0.86, specificities of 0.89 to 0.94, test-effectiveness measures approaching 3.0, and composite ROC areas of 0.91 to 0.92. Limiting analysis to studies that enrolled consecutive patients and those in which interpretation of the noninvasive tests was independent of the angiograms did not substantially change our results. CONCLUSIONS: Carotid duplex ultrasonography, carotid Doppler ultrasonography, and magnetic resonance angiography are all similarly successful at predicting 100% carotid artery occlusion and 70% stenosis. Other factors, such as cost, availability, and local experience may influence the decision to use these tests to screen for carotid artery atherosclerosis that may respond to surgery.