[R-meta] Accounting for baseline differences in meta-analysis

[Gerta Ruecker]

Dear Michael,

That's exactly what I wrote in my earlier post below. The new problem 
Gladys describes is that the baseline value are often missing, thus 
accounting for them would reduce sample size and thus precision (even if 
some missing data approaches would be used).

Best,

Gerta

Am 02.02.2021 um 11:15 schrieb Michael Dewey:
> Dear Gladys
>
> If I understand this correctly in a randomised study you can analyse 
> the post treatment values alone or take into account any baseline 
> value you wish. You may get a more precise result if you adjust for 
> baseline.
>
> Michael
>
> On 02/02/2021 08:57, Gladys Barragan-Jason wrote:
>> Dear Gerta,
>> Thanks for your response. I also realized that most of the time 
>> papers do not report the pre-treatment and/or the pre-control values. 
>> Sometimes they just say that the values are not different but do not 
>> report thoses, but more often they do not measure it at all.  Is 
>> there any way to take this into account?...I am not sure about how to 
>> deal with presence vs. absence of such values in the meta-analysis or 
>> whether this just needs to be discussed as a potential limitation.
>> Thanks a lot for your response.
>> Gladys
>>
>> Le jeu. 28 janv. 2021 à 12:35, Dr. Gerta Rücker 
>> <ruecker using imbi.uni-freiburg.de <mailto:ruecker using imbi.uni-freiburg.de>> 
>> a écrit :
>>
>>     Dear Gladys,
>>
>>     An obvious approach would be to take the post values (or,
>>     equivalently, the change scores) as an outcome, and the baseline
>>     values as a covariate in a metaregression model.
>>
>>     Best,
>>
>>     Gerta
>>
>>     Am 28.01.2021 um 10:49 schrieb Gladys Barragan-Jason:
>>>     Dear all,
>>>     I would like to know how to take the baseline difference into
>>>     account in meta-analysis of the impact of a treatment on
>>>     experimental data in which the baseline of the control group is
>>>     different from the baseline of the treatment.
>>>     For now, I am using the post- means and SD of the control and the
>>>     treatment group (and the rma.mv <http://rma.mv> function) and also
>>>     the pre-post values of the treatment group but I don't think this
>>>     is correct and I am not sure how to proceed.
>>>     Any advice?
>>>     Thanks a lot in advance.
>>>     Best regards,
>>>     Gladys
>>>
>>>     --
>>>     ------------------------------------------
>>>
>>>     Gladys Barragan-Jason, PhD.  Website
>>> <https://sites.google.com/view/gladysbarraganjason/home>
>>>
>>>     Station d'Ecologie Théorique et Expérimentale (SETE)
>>>
>>>     CNRS de Moulis
>>>
>>>     image.pngimage.png
>>>
>>>
>>>
>>>
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>>
>>
>>
>> -- 
>>
>> ------------------------------------------
>>
>> Gladys Barragan-Jason, PhD. ____ Website 
>> <https://sites.google.com/view/gladysbarraganjason/home>
>>
>> Station d'Ecologie Théorique et Expérimentale (SETE)____
>>
>> CNRS de Moulis____
>>
>> image.pngimage.png____
>>
>>
>>
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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

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