[R-meta] meta-analysis of 0 events in one or both arms

Gerta Ruecker ruecker @end|ng |rom |mb|@un|-|re|burg@de
Fri Apr 3 11:34:17 CEST 2020

Dear Irene,

Double-zero studies can be safely ignored for relative measures such as 
RR and OR, because they do not contribute to the likelihood (see, for 
example, https://www.ncbi.nlm.nih.gov/pubmed/32065224 ).

Studies with a zero in only one arm (single-zero studies) are included 
with the Mantel-Haenszel method, without need of a continuity 
correction. In the meta package, to avoid a continuity correction, one 
has to set incr = 0. The Peto method includes one-zero studies always 
without a continuity correction, but likewise ignores double-zero studies.

The sentence you cited from the meta help page means that in order to 
include studies with zero events in both groups you have to set 
allstudies=TRUE. You need a continuity correction. If not, they are 

In netmeta, it is similar: If you set allstudies=TRUE, all studies are 
included, but with an increment, by default incr=0.5.

For network meta-analysis, instead of using the netmeta() function, you 
may consider using function netmetabin(), which uses one-stage methods 
like the Mantel-Haenszel method. See example(netmetabin).

Summarizing this,

  * it is no problem to include single-zero studies without needing a
    continuity correction when using the Mantel-Haenszel estimator (or
    other one-stage methods).
  * Double-zero studies can only be included by using an increment
  * But this is not necessary/recommended because they are not
    informative for relative measures.



Am 03.04.2020 um 10:15 schrieb Bighelli, Irene:
> Dear all,
> I am dealing with meta-analysis and network meta-analysis of dichotomous data where the number of event in one or both arms is = 0. I would like to find a way to include these studies in the analysis, without applying a continuity correction. Is it possible?
> I know there are different ways to deal with this,
> in metabin: I understand that a continuity correction is applied by default (https://cran.r-project.org/web/packages/meta/meta.pdf page 60-62<https://cran.r-project.org/web/packages/meta/meta.pdf%20page%2060-62>): "For studies with a zero cell count, by default, 0.5 is added to all cell frequencies of these studies; if incr is "TACC" a treatment arm continuity correction is used instead (Sweeting et al., 2004; Diamond et al., 2007). For odds ratio and risk ratio, treatment estimates and standard errors are only calculated for studies with zero or all events in both groups if allstudies is TRUE." Does it mean that with allstudies=TRUE only studies with zero events are counted, and the ones with some events excluded?
> in netmeta: I read in the manual of the pairwise function (https://cran.r-project.org/web/packages/netmeta/netmeta.pdf), where the argument "allstudies=TRUE" allows to include in the calculations such studies ("A logical indicating if studies with zero or all events in two treatment arms are to be included in the meta-analysis"). However, I was not able to find a description of how this works, and whether it applies a continuity correction.
> Thanks a lot in advance for your help,
> Irene
> ________________
> Irene Bighelli  PhD
> Technical University of Munich | School of Medicine | Klinikum rechts der Isar
> Department of Psychiatry and Psychotherapy
> Section for Evidence Based Medicine in Psychiatry
> Ismaningerstr. 22, 81675 M�nchen, Germany
> Tel: +4908941404243
> Mail: irene.bighelli using tum.de<mailto:irene.bighelli using tum.de>
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Dr. rer. nat. Gerta Rücker, Dipl.-Math.

Institute of Medical Biometry and Statistics,
Faculty of Medicine and Medical Center - University of Freiburg

Stefan-Meier-Str. 26, D-79104 Freiburg, Germany

Phone:    +49/761/203-6673
Fax:      +49/761/203-6680
Mail:     ruecker using imbi.uni-freiburg.de
Homepage: https://www.imbi.uni-freiburg.de/persons/ruecker/person_view

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