Interrater reliability of plaque morphology classification in patients with severe carotid artery stenosis

Objective - Ultrasonographic assessment of carotid artery plaque morphology is widely used to identify patients at high risk: for stroke. However, the reliability of plaque analysis in high-grade stenosis is uncertain. We det ermined the interrater reliability of sonographic plaque morphology analysi s in patients with severe carotid artery stenosis. Material nnd methods - D uplex Doppler was performed on 114 patients with 80-99% stenosis of the int ernal carotid artery using a Siemens Quantum 2000 D with a handheld 7.5 MHz transducer. B-mode pictures with and without color coding were printed on a Sony color video printer UP-5000 W. Three raters independently evaluated plaque echolucency, heterogeneity, calcification, and surface structure. In terrater agreement was calculated by a jackknife procedure generating kappa values and two-sided 95% confidence intervals. Results - Kappa values and 95% confidence intervals were 0.05 (-0.07 to 0.16) for plaque surface struc ture, 0.15 (0.02 to 0.28) for plaque heterogeneity, 0.18 (0.09 to 0.29) for plaque echogenicity, and 0.29 (0.14 to 0.39) for plaque calcification. The upper bounds of all of the confidence intervals were below the 0.40 level suggested for minimal reliability. Conclusion - The low interrater agreemen t indicated that unaided visual assessment of static B-mode pictures to ass ess plaque morphology in patients with severe carotid artery stenosis is no t reliable. Other evaluation procedures and standardized criteria, as yet u ndeveloped, are needed to improve reliability.