Validation of a new ultrasound method for the measurement of carotid artery intima medial thickness and plaque dimensions.

Background: Carotid ultrasound is an accepted method for the detection of subclinical atherosclerosis. Valid methods that allow quantitation of carotid atheroma burden may be useful for stratifying risk.

Objective: To validate the results of intima medial thickness (IMT) and plaque measurements using a newly created software algorithm by comparing them with those obtained using a previously validated method.

Methods: Carotid ultrasound videotapes (n=24) were analyzed by experienced observers using a validated method and a new method. Ultrasound parameters were compared by measuring the difference +/- SD to yield indexes of accuracy and precision. Performance was also assessed using correlation and Bland-Altman analyses.

Results: Average IMT (n=24), plaque area (n=46), and several indexes that integrate IMT and plaque measurements were all found to be comparable with measurements obtained using the previously validated method. For example, the plaque area showed excellent accuracy and precision (-0.17+/-2.0 mm2, P=0.56), excellent correlation (r=0.98, standard error of the estimate = 2.01 mm2, P<0.001) and no evidence of bias using Bland-Altman analyses (Spearman's rho = 0.04, P=0.82).

Conclusions: A new algorithm for the quantitation of carotid atheroma burden yields results that are comparable with those of a previously validated and widely used method. Availability of valid tools for measuring carotid ultrasound should facilitate the incorporation of this procedure into clinical risk stratification paradigms.