What is the accuracy and reliability of ultrasound to detect clinically important CAS?
We found two meta-analyses on the accuracy of ultrasound to detect clinically important stenosis. A recent meta-analysis included studies published from 1993 through 2001, and estimated the accuracy of carotid duplex ultrasound using digital subtraction angiography as the reference standard.29 Carotid duplex ultrasound had an estimated sensitivity of 86% (95% CI, 84% to 89%) and a specificity of 87% (95% CI, 84% to 90%) for detecting CAS of 70%–99%.29 A second meta-analysis of carotid duplex ultrasound found similar sensitivity and specificity for carotid duplex ultrasound to detect 70% or greater stenosis, 90% (95% CI, 84–94%) and 94% (95% CI, 88–97%) respectively.30 To detect CAS ≥ 50%, the authors suggested a cut-point that had a sensitivity of 98% and a specificity of 88%. Reading from a graph in this paper and using the same cut point as was suggested for detecting ≥ 70% CAS, we estimate that the sensitivity of carotid duplex ultrasound to detect CAS ≥ 60% is about 94%, with a spe
