Duplex criteria for determination of 50% or greater carotid stenosis

Recently the North American Symptomatic Carotid Endarterectomy Trial invest igators reported a benefit of carotid endarterectomy compared with medical therapy for symptomatic patients with 50% or greater carotid stenosis. This has necessitated the development of screening parameters for diagnosis of 50% or greater carotid stenosis on the basis of the reference standards use d in the study by the North American Symptomatic Carotid Endarterectomy Tri al. The duplex scans and arteriograms of 110 patients (210 carotid arteries ) were reviewed by blinded readers. Duplex measurements of peak systolic ve locity and end diastolic velocity were recorded, and the ratio of these vel ocities in the internal and common carotid arteries was calculated. The cri teria determined for detection of 50% or greater stenosis were as follows: peak systolic velocity of the internal carotid artery greater than 170 cm/s (sensitivity, 92%; specificity, 90%; positive predictive value, 92%; negat ive predictive value, 90%; and accuracy, 91%); end diastolic velocity of th e internal carotid artery greater than 60 cm/s (sensitivity, 92%; specifici ty, 86%; positive predictive value, 95%; negative predictive value, 79%; an d accuracy, 91%); ratio of peak systolic velocity of the internal carotid a rtery to peak systolic velocity of the common carotid artery greater than 2 (sensitivity, 93%; specificity, 75%; positive predictive value, 83%; negat ive predictive value, 89%; and accuracy, 85%); and ratio of end diastolic v elocity of the internal carotid artery to end diastolic velocity of the com mon carotid artery greater than 2.4 (sensitivity, 96%; specificity, 79%; po sitive predictive value, 88%; negative predictive value, 92%; and accuracy, 89%). It is concluded that 50% or greater carotid artery stenosis can be r eliably determined by duplex criteria. The use of receiver operating charac teristic curves allows the individualization of duplex criteria to the clin ical situation.