DETERMINATION OF DUPLEX-DOPPLER ULTRASOUND CRITERIA APPROPRIATE TO THE NORTH-AMERICAN SYMPTOMATIC CAROTID ENDARTERECTOMY TRIAL

Background and Purpose The North American Symptomatic Carotid Endarter ectomy Trial (NASCET) demonstrated the benefit of carotid endarterecto my for symptomatic patients with greater than or equal to 70% carotid stenosis. Screening for detection of significant carotid occlusive dis ease has relied on duplex Doppler imaging. However, traditional duplex categories (50% to 79%, 80% to 99%) are not directly applicable to NA SCET. We sought to evaluate duplex criteria for determination of great er than or equal to 70% carotid stenosis. Methods Duplex scans and art eriograms 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 systo lic and end-diastolic velocity (PSV, EDV) were recorded, and ratios of velocities in the internal and common carotid arteries (ICA, CCA) wer e calculated. Receiver-operator characteristic (ROC) curves of sensiti vity, specificity, positive and negative predictive values (PPV, NPV), and accuracy were determined. Results Interobserver agreement for mea surement of arteriographic stenosis was ''almost perfect'' (kappa=0.86 ). The criteria chosen for detection of greater than or equal to 70% s tenosis were PSVICA>210 cm/s (sensitivity, 94%; specificity, 77%; PPV, 68%; NPV, 96%; accuracy, 83%), EDV(ICA)>70 cm/s (sensitivity, 92%; sp ecificity, 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 d uplex Doppler ultrasound. Individual vascular laboratories must valida te their own results.