Clinical Question: Can noninvasive imaging replace invasive imaging in patients with suspected carotid artery disease?

Setting: Various (meta-analysis)

Study Design: Systematic review

Synopsis: Two members of a research team searched MEDLINE and EMBASE and hand-searched several journals to identify 41 prospective studies of at least 20 patients with suspected carotid artery disease who underwent one or more noninvasive tests and invasive angiography. Any disagreements were settled by discussion with a third reviewer. Similarly, two reviewers extracted the data, and a third reviewer arbitrated any discrepancies. The identified studies included a total of 2,541 patients. Overall, contrast-enhanced magnetic resonance angiography (CE-MRA) performed best, although computed tomographic angiography, magnetic resonance angiography, and Doppler ultrasonography also performed well. The authors found some variability in test performance, mainly because of differences in accuracy on the basis of the degree of stenosis. Depending on the degree of stenosis, CE-MRA provided the most diagnostic information (positive likelihood ratio ranged from 13 to 26, and negative likelihood ratio from 0.04 to 0.24). Generally speaking, the noninvasive tests were not as accurate in patients with moderate stenosis (50 to 69 percent). Because this group also has a narrow surgical risk-benefit margin, diagnostic certainty is critical. Finally, CE-MRA results may be biased because of small study sizes and, as a new technology, the potential for reporting overly positive studies.

Bottom Line: Noninvasive testing, especially CE-MRA, compares favorably with invasive angiography. Because noninvasive testing appears to be less accurate in patients with less severe stenosis, a reasonable strategy might begin with CE-MRA. If it demonstrates a greater than 70 percent stenosis, the diagnosis is confirmed. If the stenosis appears to be less than 70 percent, invasive angiography might be considered. This diagnostic approach needs formal evaluation. (Level of Evidence: 1a–)