Specificity of MR Angiography as a Confirmatory Test for Carotid Artery Stenosis: Is It Valid?

Feasibility of intravenous flat panel detector CT angiography for intracranial arterial stenosis

BACKGROUND AND PURPOSE

I.v. FDCT angiography is an emerging technology for the detection of intracranial vascular disease. This study was conducted to determine the feasibility of i.v. FDCT in estimating major atherosclerotic intracranial arterial stenosis with DSA as the reference.

MATERIALS AND METHODS

DSA and i.v. FDCT were performed simultaneously in patients with transient ischemic attack or acute cerebral infarction. The degree and length of stenosis were measured. The stenotic vessels were categorized into 4 groups by the grade of stenosis: normal (<30%), mild (30%-49%), moderate (50%-69%), or severe (>70%). The vessels of the normal group were excluded from analysis to reduce spectrum bias. Measurement of vessels was recorded by using an electric ruler by a qualified endovascular neurosurgeon and a neuroradiologist.

RESULTS

Eight hundred forty-two vessel segments in 69 patients were calculated. Mild (n = 56), moderate (n = 47) and severe stenosis (n = 46) groups were analyzed. I.v. FDCT had a sensitivity of 97.6%, specificity of 96.9%, and negative predictive value of 96.9% for detecting ≥50% stenosis and respective values of 91.9%, 98.2%, and 97.4% for depicting ≥70% stenosis. The difference of stenotic length between the 2 tests was not significant as an increase in the severity of stenosis (Spearman rank correlation test; r = -0.12, P = .13).

CONCLUSIONS

I.v. FDCT can be a feasible alternative as a noninvasive method for evaluating stenosis of the major intracranial arteries.

Carotid artery stenosis: accuracy of noninvasive tests--individual patient data meta-analysis

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.