[R-meta] Question about the metafor package

Mon, Aug 17, 2020 9:28 AM

Dear Safa,

You could just do:

mods = ~ Age_TRT_mean + Age_Control_mean + male_TRT_pc + male_Control_pc

(I think this is what you meant).

Since 'yi' is a standardized mean difference here (i.e., it reflects the difference between the two groups), one could also consider a model that directly relates the size of the group difference to the *difference* in the mean age and the *difference* in the proportion of males in the two groups. That would be:

mods = ~ I(Age_TRT_mean - Age_Control_mean) + I(male_TRT_pc - male_Control_pc)

or you could compute these differences beforehand and then include them in the model.

Best,
Wolfgang

-----Original Message-----
From: R-sig-meta-analysis [mailto:r-sig-meta-analysis-bounces at r-project.org]
On Behalf Of Safa Aouinti
Sent: Monday, 17 August, 2020 18:14
To: r-sig-meta-analysis at r-project.org
Subject: [R-meta] Question about the metafor package

Dear all,

I would like to generate a meta-regression using the function rma (package
metafor)?with mods option and I have a question about how we can precise in
mods the covariates in each group (TRT and control) ?

This is an extract of my data and my code:

metadata <- data.frame(? ?Study=factor(c("[Study1, 2008]", "[Study2, 2013]",
"[Study3, 2018]", "[Study4, 2015]")),
? ? ? ? ? ? ? ? ? ? ? ?????????????????N_TRT= c(86, 43, 12, 675),
? ? ? ? ? ? ? ? ? ? ? ?????????????????N_Control=c(55, 86, 23, 264),
? ? ? ? ? ? ? ? ? ? ? ?????????????????mean_TRT= c(12.72, 13.4, 17.58,
31.68),
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?SD_TRT= c(2.56, 0.6, 2.67, 5.3),
? ? ? ? ? ? ? ? ? ? ? ?????????????????mean_Control= c(14.5, 15.3, 18.48,
33.95),
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? SD_Control= c(2.04, 0.3, 1.34,
4.48),
? ? ? ? ? ? ? ? ? ? ? ?????????????????Age_TRT_mean= c(19.2, 23.5, 24.5,
18.49),
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?Age_TRT_SD= c(2.6, 3.8, 3.1, 4.25),
? ? ? ? ? ? ? ? ? ? ? ?????????????????male_TRT_pc= c(57, 27.9, 100, 57.6),
? ? ? ? ? ? ? ? ? ? ? ?????????????????Age_Control_mean= c(21.2, 29.2,
27.04, 19.77),
? ? ? ? ? ? ? ? ? ? ? ????????????????Age_Control_SD= c(6.1, 6.7, 2.91,
4.72),
? ? ? ? ? ? ? ? ? ? ? ?????????????????male_Control_pc= c(60, 46.5, 100,
51.5)
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?)

dat1 <- escalc(measure="SMD", m1i= mean_TRT, sd1i= SD_TRT, n1i=N_TRT,
? ? ? ? ? ? ? ?m2i=mean_Control, sd2i=SD_Control, n2i=N_Control,
data=metadata, digits = 2)

res <- metafor::rma(data = dat1,
? ? ? ? ? ? ? ? ? ? yi = yi, # effect size
? ? ? ? ? ? ? ? ? ? vi = vi,
? ? ? ? ? ? ? ? ? ? method = "DL",mods=~............,
? ? ? ? ? ? ? ? ? ? slab = Study)

I would like to precise in the meta-regression (in mods option) the age in
the group TRT (Age_TRT), the age in the group control?(Age_control_pc), the
percentage of males in the group TRT (male_TRT_pc) and the percentage of
males in the group control (male_control_pc). Is-it possible ? or it should
be treated differently ?

The purpose of this meta-regression is to compare the mean difference of a
medical test between two groups (treatment 'TRT' and control) and see if the
age and the gender (male percentage) influence the results.

Thank you in advance for your help !

Best regards.
--

Safa Aouinti
Ph.D. in applied Mathematics and Statistics

[R-meta] Question about the metafor package

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