Reproducibility of carotid ultrasound measurements in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) at baseline

Carotid artery assessment by ultrasound is a non-invasive evaluation of subclinical atherosclerosis and a predictor of cardiovascular events. However, ultrasound examinations are operator-dependent. In the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil), ultrasound images have been acquired from more than 10,000 participants. In this article, we describe the reproducibility of carotid intima-media thickness (CIMT), carotid plaque detection, and carotid plaque score (defined as the number of arterial sites with plaques) using ELSA-Brasil protocol, in a subset of 118 participants. Two board-certified radiologists and a trained technician read carotid images. We calculated intra- and inter-observer intraclass correlation (ICC) for CIMT values. We also present kappa coefficients for plaque detection and weighted kappa coefficients for carotid plaque score. Participants were aged 58.2±6.6 years, and 60 (50.8%) were men. For common carotid artery CIMT measurements, intra- and inter-observer ICC values were very good to excellent, ranging from 0.90 (95% confidence interval [95%CI]: 0.72-0.95) to 0.98 (95%CI: 0.97-0.99). For carotid plaque, intra- (0.96 [95%CI: 0.96-0.96]) and inter- (0.99 [95%CI: 0.99-0.99]) observer weighted kappa coefficients were very good. Intra- and inter-observer Kappa coefficients for the presence of plaques by site were good to very good, ranging from 0.69 to 1.00. In conclusion, we found very good reproducibility for carotid plaque score and CIMT measurements in the ELSA-Brasil at baseline. These results are comparable to the best findings from similar large cohorts that analyzed carotid ultrasound data.