Introduction: Common carotid artery (CCA) intima-media thickness (IMT), lumen diameter, and maximum plaque thickness were assessed on ultrasound images. The objective of the study was to evaluate the intra- and inter-reader reproducibility of the measurements following a standardised protocol.
Methods: Two readers performed the off-line measurements on B-mode ultrasound images of the distal CCA, in a randomly selected subset (n = 60) from a Flemish population cohort (FLEMENGHO). We calculated the coefficient of variation, the interclass correlation coefficient (ICC) and reproducibility according to the Bland-Altman method.
Results: The intra-reader bias for the measurements of left and right side CCA IMT were -0.003 ± 0.04 mm (p = 0.55) and 0.01 ± 0.04 mm (p = 0.03), respectively. The intra-reader bias of the lumen diameter was -0.04 ± 0.25 mm (p = 0.27) for the left and 0.02 ± 0.22 mm (p = 0.45) for the right side. The measurements for the maximum plaque thickness showed no intra-reader differences with bias 0.07 ± 0.2 mm (p = 0.26) for the left and -0.03 ± 0.2 mm (p = 0.55) for the right side. The inter-reader analysis showed good reproducibility for the left and right side CCA IMT with bias 0.004 ± 0.06 mm (p = 0.57) and -0.008 ± 0.05 mm (p = 0.19), respectively, but the lumen diameter measurements showed inter-reader differences, with bias 0.17 ± 0.27 mm (p < 0.0001) for the left and 0.10 ± 0.21 mm (p = 0.0006) for the right side. The inter-reader bias for the maximum plaque thickness were 0.07 ± 0.2 mm (p = 0.21) and -0.1 ± 0.4 mm (p = 0.26) for the left and right side, respectively.
Conclusion: The results demonstrated a reliable reproducibility of carotid wall structural measurements, allowing for an adequate further analysis of the entire population cohort.
Keywords: Carotid artery; Carotid plaques; Intima-media thickness; Reproducibility study.