Reliability of ultrasonography in detecting flow mediated dilation.

The reproducibility, interobserver and intraobserver variability of brachial artery flow-mediated dilation (FMD) has previously been reported. However, no study has compared the brachial artery FMD, detected by ultrasonography, simultaneously with reference imaging technique. The aim of this study was to assess the precision and accuracy of ultrasonography in detecting FMD compared to angiography. The study population consisted of 40 patients (13 females, mean age 56 +/- 8 years) who underwent elective diagnostic coronary angiography. The ultrasonographic FMD (USFMD) measurements have been performed according to established standards with the subjects laying on the angiography table. Selective left brachial angiography was performed while ultrasonographic measurements of the brachial artery were obtained at baseline and during reactive hyperemia. To assess precision, USFMD was compared with angiographic FMD (AGFMD) by linear regression. The accuracy of the ultrasonographic measurement in comparison to the angiographic measurement was assessed by the Bland and Altman analysis. The mean +/- SD of the testing USFMD and AGFMD measurements were 14.1 +/- 7.3 and 14.7 +/- 7.8%, respectively. Linear regression indicated a high correlation (r = 0.93, P < 0.0001) between ultrasonographic and angiographic measures, with a standard error of estimate of 2.7%. Agreement between measurements was reasonable (95% of limits of agreement, -5.481 to 4,674%). Ultrasonography seems to be reliable technique in detecting FMD.