Validity of duplex ultrasound as a diagnostic modality for internal carotid artery disease

There is an increasing trend to rely on duplex ultrasound rather than angio graphy to measure an internal carotid artery stenosis. The aim of this stud y was to determine the validity of ultrasound assessment of carotid stenosi s performed in community based vascular laboratories. We compared ultrasoun d with angiography in 225 patients referred to us for carotid intervention. Mild lesions were diagnosed by ultrasound with a sensitivity of 54%, speci ficity of 89%, and a positive predictive value of 89% compared with angiogr aphy. Severe lesions had a sensitivity of 93%, a specificity of 67%, and a positive predictive value of 45%. Receiver operator characteristic curves d emonstrated the optimal ultrasound cut-off value of 66% stenosis as a predi ctor of >60% stenosis measured angiographically, is associated with a false positive rate of 38%, and a false negative rate of 9%. Similarly, if a cut -off of 76% on ultrasound is used to predict >70% stenosis measured angiogr aphically, it would be associated with a 29% false positive rate and a fals e negative rate of 11%. Despite the value of non-invasive testing for carot id disease, duplex ultrasonography performed in non-accredited and some acc redited laboratories may produce highly variable results. Using ultrasound as the sole diagnostic test to determine the severity of a carotid stenosis may result in a high number of inappropriate operations and a large propor tion of patients who may not be offered treatment due to false negative dia gnoses. Cathet Cardiovasc Intervent 2001;52:9-15. (C) 2001 Wiley-Liss, Inc.