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Updated: Apr 23, 2026
Ultrasound Assessment of Flow-Mediated Dilation of the Brachial and Superficial Femoral Arteries in Rats
Published on: November 3, 2016
Potentially spurious correlations between arterial size, flow-mediated dilation, and shear rate
Fabrizio Veglia1, Mauro Amato2, Marta Giovannardi2
1From Centro Cardiologico Monzino IRCCS, Milan, Italy (F.V., M.A., M.G., A.R., C.C.T., B.F., E.T., D.B.); and Dipartimento di Scienze Farmacologiche e Biomolecolari, Università di Milano, Milan, Italy (E.T., D.B.). fabrizio.veglia@ccfm.it.
Widely reported correlations between flow-mediated dilation, artery diameter, and shear rate may be spurious. Adjusting for artery size significantly reduces differences between high-risk and low-risk groups, indicating a mathematical coupling artifact.
Area of Science:
- Cardiovascular Physiology
- Biostatistics
- Medical Research Methodology
Background:
- Indices derived from ratios of variables can introduce spurious correlations.
- Flow-mediated dilation (FMD) is a key measure of endothelial function.
- Reported correlations between FMD, baseline diameter, and shear rate are common in vascular research.
Purpose of the Study:
- To investigate the extent of spurious correlations in FMD measurements.
- To determine the influence of mathematical coupling on observed relationships between FMD, baseline diameter, and shear rate.
- To assess the impact of artery size adjustment on FMD differences in participants with varying vascular risk.
Main Methods:
- Analysis of correlations between percent flow-mediated dilation, baseline diameter, and shear rate in 315 participants.
- Application of a Monte Carlo permutation procedure to assess residual correlations.
- Statistical adjustment for the confounding effect of artery size.
Main Results:
- Observed correlation coefficients were consistent with existing literature.
- Residual correlations after permutation testing remained comparable to original findings.
- Adjusting for artery size halved the mean difference in percent FMD between high-risk and low-risk groups.
Conclusions:
- The commonly observed correlations between FMD, baseline diameter, and shear rate possess a substantial spurious component.
- Percent FMD and shear rate are mathematically coupled to artery size, contributing to these spurious correlations.
- Artery size is a critical confounder that must be accounted for in FMD analysis, particularly when comparing different risk groups.
