Initial testing for carotid stenosis should be done with a noninvasive test such as CTA, MRA, or ultrasonog- raphy rather than digital subtraction angiography, with case series finding a risk of stroke ranging Experienced stroke cen- ters typically have a risk of stroke attributable to digital subtraction angiography of <0.5%. For patients at high risk of carotid artery stenosis who can undergo surgery without delay, immediate CTA is the most cost-effective strategy.84 Using consensus interpretation criteria, carotid ultra- sonography has a sensitivity of 38.8%, specific- ity of 91.6%, and accuracy of 87.1% for 70% With the use of a 70% cutoff value for carotid stenosis, CTA and digital subtrac- tion angiography were in agreement in 78 of 81 vessels (95% CI, 90 99) in a series of patients with stroke or TIA.48 Compared with digital sub- traction angiography, a meta-analysis of studies performed in 2008 found the overall sensitivity of time-of-flight MRA for the detection of 70% to 99% internal carotid artery (ICA) stenoses to be 91.2% with a specificity of 88.3%, whereas the sensitivity of contrast-enhanced MRA was 94.6% with a specificity of 91.9%.49 4. An accurate diagnosis of ischemic stroke or TIA is essential for justifying and optimizing stroke preven- tion. Many patients will have had brain imaging in the acute setting to exclude stroke mimics and to include stroke chameleons (stroke initially thought to be an alternative diagnosis). 