# [R-meta] [netmeta] Error message in network meta-analysis: "Problem with multi-arm studies: Studies with inconsistent treatment estimates"

Rogasch, Rebecca Manuela Madeleine @1rerog@ @end|ng |rom un|-tr|er@de
Sat Feb 8 14:38:23 CET 2020

```Thank you very much for the quick Reply and your advice!

That Explanation makes a lot of sense.

I have now tried using pairwise() to calculate the SMDs:

paired<- pairwise(list(TR1, TR2),
n = list(n_TR1, n_TR2),
mean = list(Mt2TR1, Mt2TR2),
sd = list(SDt2TR1, SDt2TR2),
data = DATA1, studlab = studlab, sm= "SMD")

This is an exerpt from the data Frame;

3-arm study in Purple:

studlab treat1 treat2 n1 mean1   sd1 n2 mean2   sd2           TE      seTE   age females    severity      income
1        1   EMDR     WL 15 22.87 20.27 14 54.21 16.26  -1.65116388 0.4387386 36.54    0.76    clinical      lowmid
44     100    NET     WL 19 55.07 27.01 19 76.86 17.14  -0.94310177 0.3439769 29.40    0.31    clinical high income
45     104    NET   PsEd 17 19.10 11.70 12 21.20  9.40  -0.18860625 0.3779770 32.85    0.62    clinical      lowmid
48     107    MBI   PsEd 68 46.90 18.20 66 55.20 15.30  -0.49022797 0.1754460 47.04    0.17    clinical high income
47     107     PE   PsEd 68 50.60 18.50 66 55.20 15.30  -0.26905282 0.1735963 47.04    0.17    clinical high income
46     107     PE    MBI 68 50.60 18.50 68 46.90 18.20   0.20049752 0.1719418 47.04    0.17    clinical high income
78      11    MBI     WL NA    NA    NA NA    NA    NA  -0.48920000 0.2800000 51.80    0.99        <NA> high income

sample arms        self_exp n_total        tr_size   analysis

1  refugees    2      self-rated      29     very small completers
44 refugees    2 clinician-rated      38     very small        ITT
45 refugees    2      self-rated      29     very small        ITT
48   vetmil    3      self-rated     134          large        ITT
47   vetmil    3      self-rated     134          large        ITT
46   vetmil    3      self-rated     136          large        ITT
78 civilian    2      self-rated      71 small-moderate        ITT

However, I still get the same error message in the Network meta-Analysis.

A more detailed copy of the Output is available if needed.

Any advice is very much appreciated!

Best regards,

Rebecca

________________________________
Von: Guido Schwarzer <sc using imbi.uni-freiburg.de>
Gesendet: Freitag, 7. Februar 2020 17:49:50
An: Rogasch, Rebecca Manuela Madeleine; r-sig-meta-analysis using r-project.org
Betreff: Re: [R-meta] [netmeta] Error message in network meta-analysis: "Problem with multi-arm studies: Studies with inconsistent treatment estimates"

Hi Rebecca,

I assume the problem is related to calculating SMDs in multi-arm
studies. Each pairwise comparison (in a multi-arm study) uses a
different pooled standard deviation to calculate the SMD which leads to
inconsistent effects.

You could / should use pairwise() to calculate the SMDs which considers
the same pooled standard deviation to calculate the SMD in multi-arm
studies.

Best wishes, Guido

--
Dr. Guido Schwarzer
Institute of Medical Biometry and Statistics,
Faculty of Medicine and Medical Center - University of Freiburg

Postal address: Stefan-Meier-Str. 26, D-79104 Freiburg

Phone: +49/761/203-6668
Mail: sc using imbi.uni-freiburg.de
Homepage: http://www.imbi.uni-freiburg.de

ORCID iD: https://orcid.org/0000-0001-6214-9087
R-book: https://www.springer.com/gp/book/9783319214153

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