[R-meta] Issue with netmeta package
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) [...]
Dear Chrysostomos, 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 Ad 1) 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. Ad 2) 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 (R?cker 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 R?cker 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 R?cker 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. Best wishes, Guido Reference: R?cker G, Cates CJ, Schwarzer G. Methods for including information from multi-arm trials in pairwise meta-analysis. Res Synth Methods 2017, Jul 31. http://onlinelibrary.wiley.com/doi/10.1002/jrsm.1259/full -- 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