Interobserver and intraobserver variability of flow-mediated vasodilatation of the brachial artery

Flow-mediated endothelial-dependent vasodilatation (FMD) of the brachial artery is a method capable of detecting endothelial dysfunction. In order to implement this method in future clinical research studies, its reproducibility and precision have to be assessed. The aim of the study is to evaluate the inter- and intraobserver variability of FMD performed in our department. We investigate 40 patients. FMD is measured by two independent observers to test the interobserver variability, and repeated by the first observer to test the intraobserver variability. We compare the baseline and post-ischemic diameter of the brachial artery and the percent dilatation. The correlation coefficients for these comparisons are high (>0.92) with a significance of less than 0.001. The inter- and intraobserver variability is further tested comparing the mean values of the baseline and post ischemic diameter of the brachial artery and the percent dilatation. The absolute values of the mean paired differences and the standard deviations (SDs) of the differences are 0.02850 +/- 0.05942, P = 0.004, 0.01175 +/- 0.08177, P = 0.369 and 0.28375 +/- 1.61561, P = 0.273, respectively for the interobserver variability and 0.00475 +/- 0.04663, P = 0.523, 0.00050 +/- 0.05267, P = 0.952 and 0.15725 +/- 1.19922, P = 0.412, respectively for the intraobserver variability. It can be concluded that the inter- and intraobserver variability for FMD performed in our department is acceptable. FMD can be performed precisely and accurately, with a satisfactory reproducibility and can be safely and reliably implemented in future clinical research studies.