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Purpose: To find clinically relevant estimates of the accuracy of noninvasive imaging-Doppler ultrasonography (US), computed tomographic (CT) angiography, magnetic resonance (MR) angiography, and contrast material-enhanced MR angiography-in diagnosing both severe and moderate symptomatic carotid artery stenosis; to ascertain the effect of prespecified clinical factors and clinical setting on diagnostic accuracy; and to estimate the probability of agreement between two noninvasive tests., Materials and Methods: Original principal investigators obtained ethics approval for each data set. All data were anonymized. Individual patient data sets (IPDs) for noninvasive imaging tests were used to determine sensitivity, specificity, and agreement between the tests for symptomatic carotid artery stenosis; to compare ipsilateral with contralateral arteries; to compare IPDs with literature estimates; to compare routine audit and research data; and to determine the effect of age and sex on sensitivity and specificity., Results: Contrast-enhanced MR angiography was the most accurate (sensitivity, 0.85 [30 of 35]; 95% confidence interval [CI]: 0.69, 0.93; and specificity, 0.85 [67 of 78]; 95% CI: 0.76, 0.92) for 70%-99% symptomatic stenosis. Sensitivity for a 50%-69% stenosis was poor, although data were limited. Sensitivity and specificity were generally lower in the ipsilateral than in the contralateral artery. IPD estimates were lower than literature values. Results of comparison of research with audit-derived data were inconclusive. Neither age nor sex affected accuracy. Agreement was better between two Doppler US tests and between two contrast-enhanced MR angiographic tests than it was between Doppler US and contrast-enhanced MR angiography, except for a 70%-99% symptomatic stenosis., Conclusion: Primary studies should distinguish ipsilateral from contralateral arteries and carefully describe the patients' characteristics and study environment. The literature overestimates noninvasive imaging accuracy. More data are needed to inform physicians in routine clinical practice.

Objectives: To determine whether less invasive imaging tests [ultrasound (US), magnetic resonance angiography (MRA), computed tomographic angiography (CTA) and contrast-enhanced MRA (CEMRA)], alone or combined, could replace intra-arterial angiography (IAA), what effect this would have on strokes and deaths, endarterectomies performed and costs, and whether less invasive tests were cost-effective., Data Sources: Electronic databases covering the years 1980-2003 inclusive, updated to April 2004. Key journals from 1990 to the end of 2002., Review Methods: The authors constituted a panel of experts in stroke, imaging, vascular surgery, statistics and health economic modelling. The accuracy of less invasive carotid imaging was systematically reviewed using Standards for Reporting of Diagnostic Accuracy (STARD) methodology, supplemented by individual patient data from UK primary research and audit studies. A systematic review of the costs of less invasive tests, outpatient clinics, endarterectomy and stroke was performed, along with a microcosting exercise. A model of the process of care following a transient ischaemic attack (TIA)/minor stroke was developed, populated with data from stroke epidemiology studies in the UK, effects of medical and surgical interventions, outcomes, quality of life and costs. A survey of UK stroke prevention clinics provided typical timings. Twenty-two different carotid imaging strategies were evaluated for short- and long-term outcomes, quality-adjusted life-years (QALYs) and net benefit., Results: In 41 included studies (2404 patients, median age 60-65 years), most data were available on 70-99% stenosis. CEMRA was the most accurate [sensitivity 0.94, 95% confidence interval (CI) 0.88 to 0.97; specificity 0.93, 95% CI 0.89 to 0.96], compared with US, MRA and CTA, which were all similar (e.g. for US: sensitivity 0.89, 95% CI 0.85 to 0.92; specificity 0.84, 95% CI 0.77 to 0.89). Data for 50-69% stenoses and on combinations of tests were too sparse to be reliable. There was heterogeneity between studies for all imaging modalities except for CTA. The individual patient data (2416 patients) showed that the literature overestimated test accuracy in routine practice and that, in general, tests perform with higher sensitivity and specificity in asymptomatic than in symptomatic arteries. In the cost-effectiveness model, on current UK timings, strategies allowed more patients to reach endarterectomy very quickly, and where those with 50-69% stenosis would be offered surgery in addition to those with 70-99%, prevented most strokes and produced greatest net benefit. This included most strategies with US as first or repeat test, and not those with IAA. However, the model was sensitive to less invasive test accuracy, cost and timing of endarterectomy. In patients investigated late after TIA, test accuracy is crucial and CEMRA should be used before surgery., Conclusions: In the UK, less invasive tests can be used in place of IAA if radiologists trained in carotid imaging are available. Imaging should be carefully audited. Stroke prevention clinics should reduce waiting times at all stages to improve speed of access to endarterectomy. In patients presenting late after TIA, test accuracy is very important and US results should be confirmed by CEMRA, as patients with 50-69% stenosis are less likely to benefit. More data are required to define the accuracy of the less invasive tests, with improvements made in the data collection methods used and how data are presented. Consideration should also be given to the use of new technologies and randomised trials.

Background: Accurate carotid imaging is important for effective secondary stroke prevention. Non-invasive imaging, now widely available, is replacing intra-arterial angiography for carotid stenosis, but the accuracy remains uncertain despite an extensive literature. We systematically reviewed the accuracy of non-invasive imaging compared with intra-arterial angiography for diagnosing carotid stenosis in patients with carotid territory ischaemic symptoms., Methods: We searched for articles published between 1980 and April 2004; included studies comparing non-invasive imaging with intra-arterial angiography that met Standards for Reporting of Diagnostic Accuracy (STARD) criteria; extracted data to calculate sensitivity and specificity of non-invasive imaging, to test for heterogeneity and to perform sensitivity analyses; and categorised percent stenosis by the North American Symptomatic Carotid Endarterectomy Trial (NASCET) method., Results: In 41 included studies (2541 patients, 4876 arteries), contrast-enhanced MR angiography was more sensitive (0.94, 95% CI 0.88-0.97) and specific (0.93, 95% CI 0.89-0.96) for 70-99% stenosis than Doppler ultrasound, MR angiography, and CT angiography (sensitivities 0.89, 0.88, 0.76; specificities 0.84, 0.84, 0.94, respectively). Data for 50-69% stenoses and combinations of non-invasive tests were sparse and unreliable. There was heterogeneity between studies and evidence of publication bias., Interpretation: Non-invasive tests, used cautiously, could replace intra-arterial carotid angiography for 70-99% stenosis. However, more data are required to determine their accuracy, especially at 50-69% stenoses where the balance of risk and benefit for carotid endarterectomy is particularly narrow, and to explore and overcome heterogeneity. Methodology for evaluating imaging tests should be improved; blinded, prospective studies in clinically relevant patients are essential basic characteristics.