MR angiography effective for diagnosing carotid artery stenosis
The Journal of Family Practice. 2003 September;52(9):664-688
September 1, 2003|The Journal of Family Practice
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- BACKGROUND: Major randomized trials have demonstrated the benefit of carotid endarterectomy for patients with severe symptomatic carotid artery stenosis. This meta-analysis compared duplex ultrasound with MRA and the gold standard, digital subtraction angiography. Because digital subtraction angiography is the standard reference for selecting surgical patients, a noninvasive test with less morbidity and mortality would be preferable.
- POPULATION STUDIED: This meta-analysis included 62 articles yielding 85 separate study populations screened for carotid stenosis with MRA or duplex ultrasound. No information regarding the age, race, or comorbid disorders was given; therefore, it is unknown whether the study population is comparable to a typical family practice setting.
- STUDY DESIGN AND VALIDITY: The authors performed a literature search on PubMed using the keywords “carotid artery” and “angiography” combined with “magnetic resonance” and/or “duplex” or “ultrasound.” Additional articles were obtained using the reference lists of original and review publications. Only articles published in English between 1994 and 2001 were included in the search. They also directly contacted authors when data reporting was not sufficient for their analysis.
- OUTCOMES MEASURED: The primary outcomes measured where pooled sensitivities and specificities for MRA and duplex ultrasound. No patient-oriented outcomes were measured in this study.
- RESULTS: At a prevalence rate of 1%, MRA showed a sensitivity of 95% with a specificity of 90% (positive likelihood ratio [LR+]=9.5; negative likelihood ratio [LR–]=0.06) for severe stenosis, while duplex ultrasound demonstrated a sensitivity of 86% and a specificity of 87% (LR+ = 6.6; LR– = 0.2). Both MRA and duplex ultrasound were nearly 100% sensitive and specific at determining complete occlusion of the carotid arteries.
PRACTICE RECOMMENDATIONS
Magnetic resonance angiography (MRA) is better than duplex ultrasound for diagnosing severe (70%–99%) carotid artery stenosis. Both tests are highly accurate for diagnosing total carotid artery occlusion.
Whether this advantage translates into improved patient outcomes is not known. While cost was not addressed in this study, MRA is 2 to 3 times more expensive than duplex ultrasound.
If cost and effectiveness data support these results, then MRA and duplex ultrasound might replace digital subtraction angiography for carotid artery surgery selection.
