Evaluating the use of a portable ultrasound machine to quantify intima-media thickness and flow-mediated dilation: agreement between measurements from two ultrasound machines.

Flow-mediated dilation (FMD) and common carotid intima-media thickness (CIMT) are intermediate endpoints for cardiovascular disease. The purpose of this study was to determine whether a portable ultrasound machine was capable of valid measurements of FMD and CIMT compared with a clinic-based machine under similar conditions. Vascular images were taken on 23 apparently healthy young adults with the portable type and clinic type instruments. The analyses revealed a high level of agreement between the two machines for measurements of mean [corrected] CIMT (mean difference [MD] = -0.025 mm, limits of agreement [LOA] = -0.080, 0.029 mm), maximum [corrected] CIMT (MD = 0.001 mm, LOA = -0.065, 0.065 mm) and FMD measures of brachial diameter (baseline MD = 0.199 mm, LOA = -0.210, 0.608 mm, maximum MD = 0.218 mm, LOA = -0.162, 0.597 mm). Reasonable agreement was found for %FMD measurements (MD = 0.27%, LOA = -4.91, 5.44%). The within-machine coefficient of variation results for mean [corrected] CIMT (5.0%), maximum [corrected] CIMT (4.3%), baseline (6.3%) and maximum (5.4%) brachial diameter and %FMD (30.1%) were comparable with normal within-subject variation. We conclude that the portable ultrasound machine can provide measurements of FMD and CIMT that are highly comparable with measurements obtained from a clinic-based machine under similar clinical conditions.