Accuracy of carotid duplex is laboratory specific and must be determined by internal audit.

Abstract

To assess the accuracy of carotid duplex in a single vascular laboratory at the prediction of an angiographic 70% internal carotid artery stenosis. 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. Peak systolic velocity was used as a primary end-point in carotid duplex examinations with a PSV > 130 cm/s used as an indication for angiographic assessment. Biplanar arch aortography and selective carotid catheterisation were performed as indicated and diameter reduction calculated by the ECST method. 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%. Applying duplex criteria from one centre to another is inappropriate. Laboratory specific audit of duplex and angiography is essential before deciding to abandon preoperative angiography for carotid disease.