Neuroepidemiology
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BACKGROUND AND RELEVANCE: Intracranial atherosclerosis is responsible for 70,000 ischemic strokes each year in the USA. Noninvasive testing such as transcranial Doppler ultrasound (TCD) and magnetic resonance angiography (MRA) to identify intracranial atherosclerosis is in widespread use, but has not been rigorously validated against the gold standard, catheter angiography. The recently NIH-funded Warfarin-Aspirin Symptomatic Intracranial Disease (WASID) trial will compare warfarin with aspirin for stroke prevention in patients with intracranial atherosclerosis. WASID requires performance of angiography along with TCD and MRA, providing an opportunity to critically evaluate these noninvasive tests. ⋯ Central readings will be used to validate the cutpoints and to develop measures of negative predictive value, and inter- and intra-observer variability. Sensitivity and specificity will be determined after adjustment for verification bias and employed in receiver-operator characteristic analyses. SONIA will use these techniques to develop TCD and MRA cutpoints that minimize the clinical consequences of test errors occurring in the noninvasive evaluation of patients with suspected intracranial atherosclerosis.