Accuracy and Feasibility of Non-Sonographer Acquisition and Measurement of Carotid Intima–Media Thickness

Background: Carotid intima–media thickness (IMT) is a marker of subclinical atherosclerosis and may be valuable in guiding primary prevention therapy. Equipment miniaturisation and automation have improved the feasibility of use in primary care. We sought the feasibility and accuracy of training non-sonographers to perform imaging and measurement of IMT. Methods: We studied 82 primary prevention patients (29 men; 51 ± 6 years, Framingham 5 year risk 2.6 ± 2.1%). A trained study nurse and an experienced sonographer acquired IMT in the far wall of the common carotid artery within 2 cm of the bifurcation in three planes. Images were measured off-line using automated edge tracking software by both observers. Image quality was assessed by an independent observer using a Likert score. Bland–Altman analysis, paired t-tests and linear regression analysis were used to compare results. Results: Each observer measured 492 loops. Mean IMT was 0.63 ± 0.11 mm. Image quality was significantly higher for the sonographer; there was no significant difference in feasibility of measurement (98% vs. 96%; p = NS). Linear regression showed high concordance for the left (R2 = 0.97), right (R2 = 0.91) and mean IMT (R2 = 0.96) (all p < 0.0001). Paired differences between observers were low for left (0.012 ± 0.02), right (0.016 ± 0.03) and mean IMT (0.013 ± 0.02) (all p < 0.0001). Bland–Altman analysis showed minimal bias and 95% CI within 0.04 mm. Conclusions: Imaging and measurement of carotid IMT by a trained nurse is feasible and the results show minimal differences from those obtained by an experienced sonographer. The anticipated benefits of rapid access to IMT for risk stratification in primary prevention require further study.