Prospective validation of a new duplex ultrasound criteria for 70-99% internal carotid stenosis

Background and purpose: With the exception of the European Carotid Surgery Trial, recent trials of carotid endarterectomy utilize the distal cervical internal carotid artery (ICA) as the reference vessel for calculating angiographic ICA stenosis. However, comparison studies of duplex scanning and angiography often utilized other reference sites and categories of stenosis not applicable to those employed in modern endarterectomy trials. Recognizing this, and given the interim results of the North American Symptomatic Carotid Endarterectomy Trial (NASCET), we previously performed an analysis of angiography and duplex and postulated a ratio of the peak systolic velocity (PSV) in the ICA to that in the common carotid artery (CCA) of ≥4.0 should predict a 70-99% ICA stenosis using the distal cervical CIA as the reference. In this study we prospectively tested this hypothesis. Methods: A duplex determined ICA PSV/CCA PSV ratio of ≥0.4 was prospectively and blindly compared to angiography for ability to predict a ≥70% to 99% ICA stenosis in four university affiliated laboratories. Results: An ICA PSV/CCA PSV ratio of ≥4.0 predicted a ≥70% to 99% ICA stenosis with a sensitivity of 90%, specificity of 90%, positive predictive value of 86%, negative predictive value of 94% and 90% accuracy. Conclusions: When the distal cervical ICA is the reference vessel for determining angiographic ICA stenosis a duplex derived ICA/CCA PSV ratio of ≥4.0 predicts well a ≥70-99% ICA stenosis.