Carotid intima-media thickness and hemodynamic parameters: reproducibility of manual measurements with Doppler ultrasound

To evaluate the carotid ultrasound intra- and interobserver agreements in a common clinical scenario when making manual measurements of the intima-media thickness (IMT) and peak systolic (PSV) and end diastolic (EDV) velocities in the common (CCA) and the internal carotid (ICA) arteries. Three different experienced operators performed two time-point carotid ultrasounds in 21 patients with cardiovascular risk factors. Each operator measured freehand the CCA IMT three consecutive times in each examination. The CCA and ICA hemodynamic parameters were acquired just once. For our purpose we took the average (IMTmean) and maximum (IMTmax) IMT values. Quantitative variables were analyzed with the t-student, and ANOVA test. Agreements were evaluated with the Intraclass Correlation Coefficient (ICC). IMTmean intraobserver agreement was better on the left (ICC: 0.930-0.851-0.916, operators 1-2-3) than on the right (ICC: 0.789-0.580-0.673, operators 1-2-3). IMTmax agreements (Left ICC: 0.821-0.723-0.853, operators 1-2-3; Right ICC: 0.669-0.421-0.480, operators 1-2-3) were lower and more variable. Interobserver agreements for IMTmean (ICC: 0.852-0.860; first-second ultrasound) and IMTmax (ICC: 0.859-0.835; first-second ultrasound) were excellent on the left, but fair-good and more variable on the right (IMTmean; ICC: 0.680-0.809; first-second ultrasound; IMTmax; 0.694-0.799; first-second ultrasound). Intraobserver agreements were fair-moderate for PSVs and good-excellent for EDVs. Interobserver agreements were good-excellent for both PSVs and EDVs. Overall, 95% confidence intervals were narrower for the left IMTmean and CCA velocities. Intra and interobserver agreements in carotid ultrasound are variable. In order to improve carotid IMT agreements, IMTmean is preferable over IMTmax.