Use of limited color flow duplex for a carotid screening project

BACKGROUND: Although the efficacy of carotid endarterectomy for asymptomati c carotid stenosis has been established, no cost-effective approach for ide ntification of these patients has yet been devised. The purpose of this stu dy was to develop a limited carotid duplex screening examination to be util ized for the detection of asymptomatic carotid stenoses. METHODS: Carotid screening examinations employed rapid identification of th e carotid bifurcation using color-flow duplex imaging and an immediate Dopp ler-derived velocity of the segment of the internal carotid artery with the most turbulent flow. Complete examinations were then finished using well-e stablished protocols in our accredited vascular laboratory. A total of 512 patients were referred for complete studies based upon standard indications . Criteria for at least a 50% internal carotid artery stenosis on the compl ete examination was defined as a peak systolic velocity (PSV) of at least 1 25 cm/sec. Receiver operator characteristic (ROC) curves were then construc ted to identify the optimal screening velocity criteria as compared with th e final results on the complete examination. RESULTS: Five screening examinations were technically limited yielding a to tal of 507 patients with 1,014 carotid arteries available for analysis. Com parison of screening examinations versus complete examinations for a PSV of 125 cm/sec yielded sensitivity 86%, specificity 98%, positive predictive v alue (PPV) 95%, and a negative predictive value (NPV) 93%, RCC analysis ide ntified a "cut point" of 115 cm/sec on the screening examinations to achiev e sensitivity 91%, specificity 95%, PPV 89%, and NPV 96%, Time to perform s creening examinations averaged 3.2 minutes per patient. Three patients had common carotid lesions not identified on the limited internal carotid scree ning examinations. CONCLUSIONS: Screening carotid examinations are a rapid, reliable, and rela tively inexpensive method for detection of patients with asymptomatic inter nal carotid artery stenosis. Limited screening examinations should be devel oped in each vascular laboratory and utilized in high-risk patients. Am J S urg. 1999;178:174-177. (C) 1999 by Excerpta Medica, Inc.