ACCURACY OF CAROTID DUPLEX IS LABORATORY SPECIFIC AND MUST BE DETERMINED BY INTERNAL AUDIT

Objective: To assess the accuracy of carotid duplex in a single vascul ar laboratory at the prediction of an angiographic 70% internal caroti d artery stenosis. Design: A retrospective review of all patients who underwent both carotid duplex and angiography in a 1-year period at a vascular unit which participates in the ACST trial. Methods: Peak syst olic velocity was used as a primary end-point in carotid duplex examin ations with a PSV > 130 cm/s used as an indication for angiographic as sessment. Biplanar arch aortography and selective carotid catheterisat ion were performed as indicated and diameter reduction calculated by t he ECST method. Results: The sensitivity of 130 cm/s for the detection of a 70% stenosis was 96% and the specificity 67%. If a PSV of 250 cm /s were used the sensitivity would be only 37% and specificity 96%. Co nclusions: Applying duplex criteria from one centre to another is inap propriate. Laboratory specific audit of duplex and angiography is esse ntial before deciding to abandon preoperative angiography for carotid disease.