Determination of duplex Doppler ultrasound criteria appropriate to the North American Symptomatic Carotid Endarterectomy Trial

Background and Purpose The North American Symptomatic Carotid Endarterectomy Trial (NASCET) demonstrated the benefit of carotid endarterectomy for symptomatic patients with greater than or equal to 70% carotid stenosis. Screening for detection of significant carotid occlusive disease has relied on duplex Doppler imaging. However, traditional duplex categories (50% to 79%, 80% to 99%) are not directly applicable to NASCET. We sought to evaluate duplex criteria for determination of greater than or equal to 70% carotid stenosis. Methods Duplex scans and arteriograms of 110 patients (210 carotids), performed within 1 month of each other, were reviewed by blinded readers. Arteriographic stenosis was determined by the NASCET method. Duplex measurements of peak systolic and end-diastolic velocity (PSV, EDV) were recorded, and ratios of velocities in the internal and common carotid arteries (ICA, CCA) were calculated. Receiver-operator characteristic (ROC) curves of sensitivity, specificity, positive and negative predictive values (PPV, NPV), and accuracy were determined. Results Interobserver agreement for measurement of arteriographic stenosis was ''almost perfect'' (kappa=0.86). The criteria chosen for detection of greater than or equal to 70% stenosis were PSVICA>210 cm/s (sensitivity, 94%; specificity, 77%; PPV, 68%; NPV, 96%; accuracy, 83%), EDV(ICA)>70 cm/s (sensitivity, 92%; specificity, 60%; PPV, 73%; NPV, 86%; accuracy 77%), PSVICA/PSVCCA >3.0 (sensitivity, 91%; specificity, 78%; PPV, 70%; NPV, 94%; accuracy, 83%), and EDV(ICA)/EDV(CCA)>3.3 (sensitivity, 100%; specificity, 65%; PPV, 65%; NPV, 100%; accuracy, 79%). Conclusions We conclude that greater than or equal to 70% carotid stenosis can be reliably determined by duplex Doppler ultrasound. Individual vascular laboratories must validate their own results.