Variability in measurement of internal carotid artery stenosis by arch angiography and duplex ultrasonography - Time for a reappraisal?

Objectives: to determine the inter- and intra-observer variability of ICA s tenosis measurement using duplex, ECST and NASCET methods. Design: a retrospective review of arch angiograms and carotid duplex scans in 50 patients. Materials and methods: carotid stenoses were calculated by three independen t observers according to NASCET and ECST methods. Variation between observe rs for NASCET and ECST was determined. For each observer, the variation bet ween NASCET and ECST was determined. The variation between duplex and both NASCET and ECST was determined. Results: inter-observer agreement on the degree of ICA stenosis was clinica lly and statistically good for NASCET but was poorer for ECST. For each obs erver, comparison between NASCET and ECST showed 95% limits of agreement of around 50 percentage points. Comparison of duplex with NASCET and ECST sho wed similar 95% limits of agreement. Conclusions: arch angiography allows reproducible measurement of carotid st enosis by the NASCET method between different observers. For the ECST metho d, reproducibility is not so good. Variations in results between NASCET and ECST and between angiography and duplex are significant. In view of the si milar results of the NASCET and ECST trials, this suggests that degree of s tenosis may only be a surrogate marker for outcome following carotid endart erectomy.