The negative correlation between percent flow-mediated dilation (FMD%) and baseline diameter (Dbase) has only recently been recognised as a fundamental ratio-scaling problem, which is not resolved by significance-testing of Dbase inequality between groups/conditions, nor by covariate-adjusting FMD% itself by Dbase. It is resolved appropriately by allometric scaling of the relationship between peak diameter (Dpeak) and Dbase using statistical models. Therefore, we extracted data from a seminal study on FMD%, and re-analysed it using allometric methods. We found that Dpeak did not increase as a constant proportion of Dbase, rendering FMD% a biased estimator of differences in endothelial function between artery sites (brachial vs femoral) and age-groups (children vs. adults). The allometric expression was Dpeak/Dbase≈ 0.90, rather than a simple ratio. In agreement with our previous research, a proper allometric perspective on FMD led to unbiased estimates of endothelial function, with full adjustment for the influence of baseline diameter.
|Number of pages||3|
|Publication status||Published - 1 Feb 2013|