The negative correlation between flow-mediated dilation (FMD) and arterial size may be ascribed to a mathematical artefact
Articolo
Data di Pubblicazione:
2008
Citazione:
The negative correlation between flow-mediated dilation (FMD) and arterial size may be ascribed to a mathematical artefact / C.C. Tedesco, F. Veglia, M. Amato, A. Ravani, E. Tremoli, D. Baldassarre. - In: NMCD. NUTRITION METABOLISM AND CARDIOVASCULAR DISEASES. - ISSN 0939-4753. - 18:Suppl. 1(2008), pp. S63-S63. ((Intervento presentato al 22. convegno National Congress of the Italian Society for the Study of Arteriosclerosis (SISA) tenutosi a Roma nel 2008 [10.1016/S0939-4753(08)70124-8].
Abstract:
The use of variables computed as a ratio of two measures, especially in correlation/
regression analysis, has been repeatedly criticized by statisticians.
The brachial artery Flow-Mediated Dilation (FMD%), a non invasive marker
of endothelial function widely applied in clinical studies, is a typical ratio
variable, being calculated as: (absolute diameter change after stimulus)/
(resting diameter) x 100. Unsurprisingly, significant correlations between
FMD% and resting diameter have been repeatedly reported, with coefficients
ranging from -0.2 to -0.8. These correlations have been tentatively explained
by a variety of biological reasons, but instead they may be largely accounted
by a mathematical artifact called mathematical coupling.
To test this hypothesis we used a Monte-Carlo approach by computing a
simulated FMD% in which the numerator and the denominator were lacking of
any real biological or physical relation. We started from real measurements
of resting diameters and of diameter changes obtained from 189 patients
with cardiovascular risk factors attending the Monzino Cardiology Centre in
Milan. To disrupt the biological link between the two variables, we created a
dataset of virtual patients by randomly coupling the resting diameter with the
diameter change belonging to different subjects. FMD% was then computed
from the two unrelated measures according to the above formula. The random
coupling was reiterated 1000 times. The overall mean correlation coefficient
between simulated FMD% and resting diameter was -0.170 (95% confidence
interval -0.166, -0.174), a value very close to that observed in the original
data (-0.168), and in the same range of those reported in the literature.
These results indicate that the correlation between FMD% and artery size at
rest is likely due to mathematical coupling.
Tipologia IRIS:
01 - Articolo su periodico
Elenco autori:
C.C. Tedesco, F. Veglia, M. Amato, A. Ravani, E. Tremoli, D. Baldassarre
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