Clinical carotid endarterectomy decision making: noninvasive vascular imaging versus angiography

Carotid endarterectomy (CEA) is frequently performed based solely on noninvasive vascular imaging (NVI) results (duplex ultrasound, DU; magnetic resonance angiography, MRA; CT angiography, CTA). The authors determined how often intra-arterial contrast angiography (ANGIO) alters a CEA decision as compared to NVI in clinical practice.

Reports of all NVI studies in 569 consecutive patients undergoing ANGIO at an academic medical center (AMC, n = 360) and a community hospital (CH, n = 209) over 3 years were reviewed. Patients were classified as to whether CEA was indicated based on each study. Misclassification rates, sensitivities, specificities, positive (PPV) and negative (NPV) predictive values were calculated.

CTA was performed infrequently (2.5%) and not considered further. Misclassification rates for CEA based on DU in the AMC and CH were similar. The misclassification rate for DU alone was 28% (95% CI: 24,32), and for MRA alone was 18% (95% CI: 11,25). Both NVI were done in 11% of patients, with a misclassification rate of 7.9% (95% CI: 0,16) when the two were concordant (76% of studies). DU had a sensitivity of 87% (95% CI: 83,91), specificity 46% (95% CI: 38,54), PPV 73% (95% CI: 68,78) and NPV 68% (95% CI: 60,77). MRA had a sensitivity of 75% (95% CI: 63,87), specificity 88% (95% CI: 80,96), PPV 84% (95% CI: 73,95) and NPV 80% (95% CI: 70, 90). The sensitivity of concordant NVIs was 96% (95% CI: 88,100), specificity 85% (95% CI: 65,100), PPV 93% (95% CI: 81,100) and NPV 92% (95% CI: 76,100).

These data suggest that surgical decisions should be made with caution if based on the results of noninvasive studies, particularly DU performed alone. Concordant DU and MRA results in a lower misclassification rate than either test used alone.