The inter-sonographer reliability of carotid duplex ultrasound

Carotid duplex ultrasound (CDUS) is a non-invasive technique used to assess the severity of carotid artery stenosis. It has been shown to have good correlation with digital subtraction angiography (DSA) but has been criticised for its variability. One source of this is the variation in results between studies responsible for re-validating velocity criteria to match the established treatment thresholds of internal carotid artery (ICA) stenosis. The aim of this study was to develop velocity criteria and determine the presence of inter-sonographer variation of CDUS when grading ICA stenosis in our department. Five sonographers measured the degree of ICA stenosis with CDUS in 33 patients who also underwent DSA. Receiver operator characteristic curve analysis was used to develop optimal velocity criteria for the 50%, 70% and 90% ICA stenosis thresholds as a group and for each individual sonographer. A peak systolic velocity ratio of > or = 3.25 was shown to have the highest accuracy (91.5%) for predicting a 70% stenosis. A moderate value of kappa (0.53 +/- 0.027) was calculated if the optimum velocity criterion was employed for each sonographer. There was no significant variation between the ability of sonographers to grade ICA stenosis (P > 0.05) and an excellent ICC of 0.911 was calculated. This study provides evidence to suggest that CDUS in our department is not an operator-dependant test for the investigation of ICA stenosis.