Reliability of sonographic measurements of endothelial function: Flow‐mediated dilation, blood flow velocity, resistive and pulsatility indices

Abstract

Introduction Several established and emerging sonographic measurements of vascular health are used in clinical practice and research. The aim of this study was to compare inter‐rater and intra‐rater reliability of baseline, post‐cuff‐release and percentage change of brachial artery flow‐mediated dilation (FMD); flow velocity; resistive index (RI); and pulsatility index (PI). Methods Healthy, older (45–70 years), overweight (body mass index 27–32 kg/m2) adults were sonographically assessed for arterial diameter, flow velocity and Doppler indices before and after transient ischaemia. Repeat scans were performed by either one rater (n = 10) or two different raters (n = 6) to assess reliability with intra‐class correlation coefficients (ICCs). Results Intra‐class correlation coefficients for intra‐rater reliability were highest for baseline diameter (0.97) and post‐cuff‐release diameter (0.96) but lowest for FMD (0.04). For inter‐rater reliability, ICC for baseline diameter was high (0.93). ICCs for intra‐rater and inter‐rater reliability for percentage change in velocity, percentage change in RI and percentage change in PI were similar. Conclusion Resistive index and PI showed better post‐occlusion reliability than the more common measures of FMD or peak velocity and warrants further investigation.