[R-meta] Meta-analysis Hedges g - comparisons with same placebo
P. Roberto Bakker
robertobakker at gmail.com
Thu Oct 19 19:24:32 CEST 2017
It is a nice code. Thank you.
1. N1 is not always n1i+n2i - how can I interpret this?
2. I am analysing standardized mean deference *change* - I suppose I can
use the syntax also, correct?
2017-10-19 10:26 GMT+02:00 Viechtbauer Wolfgang (SP) <
wolfgang.viechtbauer at maastrichtuniversity.nl>:
> There is also code for computing the covariance among the standardized
> mean differences in such 'multitreatment' studies here:
> -----Original Message-----
> From: R-sig-meta-analysis [mailto:r-sig-meta-analysis-
> bounces at r-project.org] On Behalf Of Gerta Ruecker
> Sent: Wednesday, 18 October, 2017 13:28
> To: P. Roberto Bakker
> Cc: r-sig-meta-analysis at r-project.org
> Subject: Re: [R-meta] Meta-analysis Hedges g - comparisons with same
> As I wrote in my response, see our paper
> <http://onlinelibrary.wiley.com/doi/10.1002/jrsm.1259/full> .
> Am 18.10.2017 um 13:10 schrieb P. Roberto Bakker:
> > Hi Gerta,
> > Thank you for your reply and suggestions.
> > Our meta-analysis is not a network meta-analysis but a 'regular', i.e.
> > pairwise. Do you have suggestion how to adjust for this?
> > Bw,
> > Roberto
> > Op 18 okt. 2017 10:41 a.m. schreef "Gerta Ruecker"
> > <ruecker at imbi.uni-freiburg.de <mailto:ruecker at imbi.uni-freiburg.de>>:
> > Dear Roberto,
> > it is a network meta-analysis what you are planning? Do you think of
> > multi-arm studies including a placebo group? If so, and if it is the
> > same placebo that is compared to several antidepressants, then I
> > there is no problem. The different placebo groups in different
> > provide independent information and network meta-analysis may in fact
> > increase precision (provided you have loops in your network), but
> > is exactly what network meta-analysis is intended to do.
> > To avoid misunderstandings: What you should not do is to use a
> > group in a multi-arm study twice in a pairwise meta-analysis without
> > adjustment.
> > For an introduction, see
> > http://onlinelibrary.wiley.com/doi/10.1002/jrsm.1259/full
> > <http://onlinelibrary.wiley.com/doi/10.1002/jrsm.1259/full> .
> > Best,
> > Gerta
> > --
> > Dr. rer. nat. Gerta Rücker, Dipl.-Math.
> > Medical Faculty and Medical Center - University of Freiburg
> > Institute for Medical Biometry and Statistics
> > Stefan-Meier-Strasse 26, D-79104 Freiburg, Germany
> > Phone +49 (0)761 2036673 <tel:%2B49%20%280%29761%202036673>
> > Fax +49 (0)761 2036680 <tel:%2B49%20%280%29761%202036680>
> > Mailruecker at imbi.uni-freiburg.de
> > <mailto:Mailruecker at imbi.uni-freiburg.de>
> > Webwww.imbi.uni-freiburg.de/biom/
> > <http://Webwww.imbi.uni-freiburg.de/biom/>
> > Am 18.10.2017 um 08:12 schrieb P. Roberto Bakker:
> > > Hi,
> > >
> > > We are conducting a meta-analysis of RCTs between
> > antidepressants and placebo and calculate Hedges g.
> > > Question:
> > > How can we deal with studies which compare different
> > antidepressants with the same placebo? Our concern is when we
> > include the different antidepressant comparisons with the same
> > placebo in the meta-analysis the placebo size will increase
> > artificially which will lead to more precise spurious results. If
> > our reasoning is correct, how can we deal this?
> > >
> > > Thank you in advance,
> > >
> > > Roberto
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