Non-invasive imaging compared with intra-arterial angiography in the diagnosis of symptomatic carotid stenosis: a meta-analysis

doi:10.1016/S0140-6736(06)68650-9

The Lancet

Volume 367, Issue 9521, 6–12 May 2006, Pages 1503-1512

https://doi.org/10.1016/S0140-6736(06)68650-9 Get rights and content

Summary

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.

Introduction

The clinical burden of stroke and transient ischaemic attack now exceeds that of coronary heart disease.¹ Effective stroke prevention is vital to reduce this burden. Carotid endarterectomy reduces the risk of ipsilateral ischaemic stroke in patients with 70–99% symptomatic carotid stenosis (North American Symptomatic Endarterectomy Trial [NASCET] criteria),² and also in some patients with 50–69% stenosis, if the stenosis is removed quickly.³

Endarterectomy trials have measured the percentage of carotid stenosis from intra-arterial angiography (IAA), an invasive, risky,⁴ and expensive procedure that could require admission to hospital. The wait for a hospital bed and limited availability of IAA delays surgery, and the strokes that the endarterectomy should prevent may occur during the wait.⁵

The carotid endarterectomy trials were undertaken during the 1980s, up to the mid-1990s. Since then, non-invasive and much less risky, carotid imaging techniques have become widely available. Techniques of Doppler ultrasound (DUS), computed tomographic angiography (CTA), magnetic resonance angiography (MRA), and contrast-enhanced MRA (CEMRA), have gradually replaced intra-arterial angiography,⁶ but on what evidence is this based? Primary studies testing non-invasive carotid imaging accuracy, while numerous, are usually small. A systematic review allows an unbiased pooling of available evidence regarding the efficacy of any given intervention, but previous systematic reviews of carotid imaging were either done some years ago,7, 8, 9, 10 only included some non-invasive imaging modalities,7, 8, 9, 11, 12, 13, 14, 15 or included studies with possibly7, 9, 10, 11 or definitely8, 16 sub-optimal study design.¹⁷

For example, studies in which researchers interpreting non-invasive tests were not blinded to the reference standard could overestimate non-invasive test accuracy.8, 16 None examined heterogeneity or undertook sensitivity analyses. Thus, it remains unclear whether, and in what circumstances, these non-invasive tests (individually or in combination) could replace IAA as the definitive diagnostic test before carotid endarterectomy.

We therefore systematically reviewed published reports to determine the accuracy of DUS, CTA, MRA, or CEMRA, alone or in combination, compared with IAA for diagnosing clinically-relevant carotid stenosis by the NASCET method in patients with carotid territory ischaemic symptoms.

Section snippets

Design

We used the Standards for Reporting of Diagnostic Accuracy (STARD) criteria and Cochrane Database of Systematic Reviews (CDSR) methods.¹⁷ Key STARD criteria include factors such as whether: the study population was relevant to the clinical question being addressed; there was a careful description of the population from which the patients were drawn, as well as actual inclusions and exclusions; recruitment and the mode of sampling were carefully described; researchers interpreting the

Results

Our search yielded 672 primary studies, of which 625 (93%) were excluded (figure 1). The main reasons for exclusion were publication between 1980 and 1986 (n=161, the Doppler ultrasound technology was not relevant to current colour Doppler techniques), other reasons such as preliminary reports of new technologies, poor methodologies (n=131), and when it was impossible to tell what proportion of patients or arteries were symptomatic (n=108). Of the remaining 47 reports, six were secondary

Discussion

Our systematic review suggests that DUS, MRA, CTA, and CEMRA all have high sensitivities and specificities for diagnosing 70–99% carotid stenosis in patients with ipsilateral carotid territory ischaemic symptoms, but might be substantially less accurate for 50–69% stenosis. CEMRA seems marginally more accurate, but it is a relatively new technique—early publications concerning new techniques tend to be over-positive—and the published studies so far come from research environments and not

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ArticlesNon-invasive imaging compared with intra-arterial angiography in the diagnosis of symptomatic carotid stenosis: a meta-analysis

Summary

Background

Methods

Results

Interpretation

Introduction

Section snippets

Design

Results

Discussion

Population-based study of event-rate, incidence, case fatality, and mortality for all acute vascular events in all areterial territories (Oxford Vascular Study)

Lancet

Analysis of pooled data from the randomised controlled trials of endarterectomy for symptomatic carotid stenosis

Lancet

From subgroups to individuals: general principles and the example of carotid endarterectomy

Lancet

Complications of cerebral angiography in patients with symptomatic carotid territory ischaemia screened by carotid ultrasound

J Neurol Neurosurg Psychiatry

Population-based study of delays in carotid imaging and surgery and the risk of recurrent stroke

Neurology

Carotid artery imaging in the United Kingdom: A postal questionnaire of current practice

Vascular

Meta-analysis of the reliability of noninvasive carotid studies

Biomed Instrument Tech

Noninvasive carotid artery testing: a meta-analytic review

Ann Intern Med

Magnetic resonance angiography and duplex scanning concordance in detecting severe carotid stenosis

Vasc Surg

Specificity of MR angiography as a confirmatory test of carotid artery stenosis

Am J Neuroradiol

A systematic review of the accuracy of diagnosis of 70% carotid artery stenosis by duplex scanning

J Vasc Invest

Use of magnetic resonance angiography to select candidates with recently symptomatic carotid stenosis for surgery: systematic review

BMJ

Systematic review of computed tomographic angiography for assessment of carotid artery disease

Stroke

Sensitivity and specificity of color duplex ultrasound measurement in the estimation of internal carotid artery stenosis: a systematic review and meta-analysis

J Vasc Surg

Duplex ultrasound and magnetic resonance angiography compared with digital subtraction angiography in carotid artery stenosis: a systematic review

Stroke

Critical review of non- or minimally invasive methods (duplex ultrasonography, MR- and CT-angiography) for evaluating stenosis of the proximal internal carotid artery

Eur J Vasc Endovasc Surg

Towards complete and accurate reporting of studies of diagnostic accuracy: the STARD initiative

Clin Radiol

The identification of bias in studies of the diagnostic performance of imaging modalities

Br J Radiol

Publication bias in clinical research

Lancet

Optimal search strategies for retrieving scientifically strong studies of diagnosis from Medline: analytical survey

BMJ

Completeness of reporting of trials published in languages other than English: implications for conduct and reporting of systematic reviews

Lancet

The development of QUADAS: a tool for the quality assessment of studies of diagnostic accuracy included in systematic reviews

BMC Med Res Methodol

Prognostic value and reproducibility of measurements of carotid stenosis: a comparison of three methods on 1001 angiograms. European Carotid Surgery Trialists' Collaborative Group

Stroke

Benefit of carotid endarterectomy in patients with symptomatic moderate or severe stenosis

N Engl J Med

The comparison of proportions from several independent samples: estimation of the marginal mean proportion

Systematic reviews of evaluations of diagnostic and screening tests

Combining independent studies of a diagnostic test into a summary ROC curve: data-analytic approaches and some additional considerations

Stats in Med

Evaluation of carotid stenosis by angiography: potential bias toward overestimated measurements introduced by prior interpretation of Doppler sonograms

Am J Neuroradiol

Comparison of MR angiography with contrast angiography for the diagnosis of carotid artery stenosis

J Assoc Phys India

Computed tomographic angiography for the evaluation of carotid artery stenosis

Stroke

Carotid stenosis: a comparison between MR and spiral CT angiography

Neuroradiol

Three-dimensional ultrasonography for the evaluation of atherosclerotic stenoses of the carotid trunk

Collegium Antropologicum

Combined use of duplex imaging and magnetic resonance angiography for evaluation of patients with symptomatic ipsilateral high-grade carotid stenosis

J Vasc Surg

Preoperative diagnosis of carotid artery stenosis: accuracy of noninvasive testing

Stroke

Outcome, observer reliability, and patient preferences if CTA, MRA, or Doppler ultrasound were used, individually or together, instead of digital subtraction angiography before carotid endarterectomy

J Neurol Neurosurg Psychiatry

Misleading funnel plot for the detection of bias in meta-analysis

Articles
Non-invasive imaging compared with intra-arterial angiography in the diagnosis of symptomatic carotid stenosis: a meta-analysis