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2017 ; 17
(1
): 44
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Standardizing effect size from linear regression models with log-transformed
variables for meta-analysis
#MMPMID28302052
Rodríguez-Barranco M
; Tobías A
; Redondo D
; Molina-Portillo E
; Sánchez MJ
BMC Med Res Methodol
2017[Mar]; 17
(1
): 44
PMID28302052
show ga
BACKGROUND: Meta-analysis is very useful to summarize the effect of a treatment
or a risk factor for a given disease. Often studies report results based on
log-transformed variables in order to achieve the principal assumptions of a
linear regression model. If this is the case for some, but not all studies, the
effects need to be homogenized. METHODS: We derived a set of formulae to
transform absolute changes into relative ones, and vice versa, to allow including
all results in a meta-analysis. We applied our procedure to all possible
combinations of log-transformed independent or dependent variables. We also
evaluated it in a simulation based on two variables either normally or
asymmetrically distributed. RESULTS: In all the scenarios, and based on different
change criteria, the effect size estimated by the derived set of formulae was
equivalent to the real effect size. To avoid biased estimates of the effect, this
procedure should be used with caution in the case of independent variables with
asymmetric distributions that significantly differ from the normal distribution.
We illustrate an application of this procedure by an application to a
meta-analysis on the potential effects on neurodevelopment in children exposed to
arsenic and manganese. CONCLUSIONS: The procedure proposed has been shown to be
valid and capable of expressing the effect size of a linear regression model
based on different change criteria in the variables. Homogenizing the results
from different studies beforehand allows them to be combined in a meta-analysis,
independently of whether the transformations had been performed on the dependent
and/or independent variables.