Validation and Reproducibility of Total Plaque Thickness in Carotid and Femoral Arteries Using Ultrasound

Objective: Plaque burden quantification by ultrasound improves cardiovascular (CV) risk prediction. However, measuring total plaque volume (TPV) with 3-D ultrasound, the current gold standard, is time consuming. In the present study we investigated the reproducibility of weighted total plaque thickness (wTPT) measured by 2-D ultrasound and its correlation with TPV.Methods: Participants in an ongoing study of subclinical atherosclerosis and CV risk with no known atherosclerotic CV disease but who were found to have one or more plaques in carotid or femoral arteries by 2-D ultrasound were included. A total of 34 women and 26 men (mean age: 59.4 y, standard deviation: 8.7) underwent primary 2-D and 3-D ultrasound examinations. Participants then underwent a 2-D ultrasound examination by another radiologist blinded to the first radiologist's findings. Finally, all participants underwent a follow-up 2-D ultrasound by the first radiologist.Results: Comparison of wTPT measurements between the 2-D studies revealed no significant difference (mean difference: 0.29 mm, 95% confidence interval [CI]: -0.48 to 1.17). Inter-observer and intra-observer analyses revealed intraclass correlation coefficients of 0.97 (95% CI: 0.96-0.98) and 1.0 (95% CI: 0.99-1.00), respectively. wTPT correlated with TPV (Spearman's rho = 0.98, 95% CI: 0.96-0.99). Elapsed time for assessing wTPT was less than that for TPV (mean difference: 36.1 min, 95% CI: 26.0-46.3).Conclusion: wTPT had high reproducibility and correlation with TPV while requiring substantially less time. Future studies addressing the role of wTPT in predicting CV disease are needed.