Diagnostic performance of duplex ultrasonography in the detection of high grade internal carotid artery stenosis

Objectives: to establish on a national basis whether the diagnostic accuracy of carotid duplex justifies carotid surgery without preoperative angiography. Design: prospective national multicentre study with 10 participating university and county hospitals. Material and Methods: one hundred and thirty-four patients, aged 69 +/- 9 years, were subjected to routine carotid duplex ultrasonography and angiography. The influence of relevant factors on the relation between ultrasonographic and angiographic variables was evaluated using multiple regression analysis. The capacity of carotid ultrasonography to detect internal carotid artery (ICA) stenosis greater than or equal to80% was assessed by receiver operating characteristic analysis. Results: the correlation between peak systolic velocity in ICA (PSVICA) and the angiographic degree of stenosis was strong and significantly influenced only by the applied Doppler angle. Accordingly, the optimal PSVICA cutpoint values for the diagnosis of ICA stenosis greater than or equal to80% (ECST method) differed substantially (2.1 and 3.2 m/s) between the two considered angle ranges (0-49degrees and 50-62degrees), the ability to identify high grade ICA stenosis being significantly better at small Doppler angles (0-49degrees). Conclusion: ultrasonographic duplex technique identifies high grade ICA stenosis with a high degree of accuracy, which can be further improved by the application of small Doppler angles and the use of angle range specific PSVICA cut-off points.