[R-meta] Issue with netmeta package
sc at imbi.uni-freiburg.de
Thu Aug 10 11:24:50 CEST 2017
Am 09.08.17 um 19:21 schrieb faniapk at gmail.com:
> Dear Chrysostomos.
> You error arises from the configuration of netmeta::pairwise(): you
> need to give your data in contrast form (one row for each comparison).
> Your 4-arm trial should contribute six rows in the dataframe, not one:
> Topiramate 50mg(route1) vs Topiramate 50mg(route2)
> Topiramate 50mg(route1) vs Topiramate 50mg(route3)
Disadvantage of this valid approach is that the network consists of
three (or more likely four) Topiramate 50mg treatments:
- Topiramate 50mg(route1)
- Topiramate 50mg(route2)
- Topiramate 50mg(route3)
- Topiramate 50mg - if any other study includes Topiramate 50mg and does
not provide information on the route
I see two alternatives:
1) Conducting a meta-regression
2) Pooling of Topiramate 50mg groups
At the moment, meta-regression is not implemented in netmeta. You could
use R package metafor for this with route as a covariate / moderator.
However, I am not sure how to include the Topiramate 50mg group from an
additional study without information on the route. You would have to
assume a certain value for the covariate.
In order to include a single Topiramate 50mg group in the network
meta-analysis, results from the three treatment groups have to be
combined. Different ways to combine or split treatment groups have been
described by us in a paper recently accepted by Research Synthesis
Methods (Rücker et al., 2017). In your case with binary outcomes,
pooling of treatment groups would simply mean to add the number of
events and number of participants (see Method 1 in Rücker et al., 2017).
Note, in your specific example, the above discussion is rather
theoretical as you have 0 events in all four treatment groups.
Therefore, even merging the three Topiramate 50mg groups (Method 1 in
Rücker et al., 2017) would result in 0 events and 33 participants
compared to 0 events and 11 participants in the Topiramate 100mg group.
In this study without any events, risk ratio and odds ratio are not
defined. Obviously, a continuity correction could be used to include the
study in the analysis, however, the resulting risk ratio / odds ratio
would largely depend on the type of continuity correction. Personally, I
do not see meta-regression as a reasonable approach with such scarce data.
Rücker G, Cates CJ, Schwarzer G. Methods for including information from
multi-arm trials in pairwise meta-analysis. Res Synth Methods 2017, Jul 31.
Dr. Guido Schwarzer (sc at imbi.uni-freiburg.de)
Institute for Medical Biometry and Statistics
Stefan-Meier-Str. 26, D-79104 Freiburg | Phone: +49 (0)761 203 6668
http://www.imbi.uni-freiburg.de | Fax: +49 (0)761 203 6680
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