The assessment of flow-mediated dilation (FMD) is widely used to quantify endothelial function. Historically, FMD was determined at 60 seconds post-cuff deflation. We investigated whether FMD would be more accurate if determined at maximum dilatory peak (MDP) than at 60 seconds in healthy subjects and subjects with type 2 diabetes mellitus (T2DM). We studied 95 healthy and 72 subjects with T2DM and assessed FMD at MDP, 60 and 90 seconds. Twenty-four healthy and 12 subjects with T2DM underwent a repeat FMD after 28 days. In healthy subjects, FMD at MDP was higher than at 60 and 90 seconds, with mean difference MDP versus 60 seconds 1.14% (95% CI: 0.6-1.7); P < .0001 and MDP versus 90 seconds 1.9% (95% CI: 1.3-2.5) with similar results in T2DM, that is, 1.0% (95% CI: 0.1-1.9) and 2.3% (95% CI: 1.3-3.2), respectively. Intraindividual variability was lowest with MDP compared with 60 and 90 seconds, that is, 15.0 versus 23.2% and 40.0%, respectively, resulting in a more than 2-fold reduction in necessary sample size. In healthy subjects and subjects with T2DM, assessment of FMD using MDP results in a more accurate and precise assessment leading to a substantial reduction in sample size.
Keywords: endothelial dysfunction; flow-mediated dilation; type 2 diabetes.