[R-meta] Meta-analysis of mean differences

Tue Feb 1 14:40:04 CET 2022

Hello, thank you all.
I don't quite understand how to test different sensitivity analyzes with different correlation coefficients. What had occurred to me was to use the values after the intervention in the two groups and do a meta-regression using the baseline LDL level as a covariate, and thus adjust the result for it, but I don't know if that would be correct.
In any case, I want to explain the case again, since out there it was interpreted as paired measurements and it is not.
I have group A and Group B, in each group I have a baseline value of LDL and the value after the intervention, and I need to meta-analyze the impact on this variable. I usually do it already having the difference between baseline and post-treatment of the two groups with their deviations, but in this case I only have these data to make a difference of means. That's why I also asked how to do it with change scores, something like that had been explained to me by gerta but I didn't understand.
Thanks a lot

Lorenzo Martín Lobo MTSAC, FACC, FESC
Especialista Jerarquizado en Cardiología
Jefe de Dpto Enf. Cardiovasculares y Cardiometabolismo Hospital Militar Campo de Mayo.
Jefe de Cardiología Hospital Militar Campo de Mayo
Ex Jefe de Unidad Coronaria Hospital Militar Campo de Mayo
Miembro Titular de la Sociedad Argentina de Cardiología
Fellow American College of Cardiology
Fellow European Society of Cardiology
Ex Miembro del Area de Investigación de la SAC
Ex Director del Consejo de Aterosclerosis y Trombosis de la SAC
Miembro Asesor del Consejo de Aterosclerosis y Trombosis de la SAC
Ex Director del Consejo de Epidemiología y Prevención Cardiovascular de la SAC

Miembro Asesor del Consejo de Epidemiología y Prevención Cardiovascular de la SAC

Experto en Lipidos de la Sociedad Argentina de Lipidos.
Miembro de la Sociedad Argentina de Lipidos.
Instructor de ACLS de la American Heart Association

________________________________
De: Michael Dewey <lists using dewey.myzen.co.uk>
Enviado: lunes, 31 de enero de 2022 08:59
Para: Martin Lobo <mlobo4370 using hotmail.com>; Viechtbauer, Wolfgang (SP) <wolfgang.viechtbauer using maastrichtuniversity.nl>; r-sig-meta-analysis using r-project.org <r-sig-meta-analysis using r-project.org>
Asunto: Re: [R-meta] Meta-analysis of mean differences

Dear Martin

I think the relevant part of the link to which Wolfgang directed you is

"In practice, one is likely to encounter difficulties in actually
obtaining those correlations from the information reported in the
articles. In that case, one can substitute approximate values (e.g.,
based on known properties of the dependent variable being measured) and
conduct a sensitivity analysis to ensure that the conclusions from the
meta-analysis are unchanged when those correlations are varied."

I suggest that you choose a range of plausible values for r and fit the
model for each. If the scientific conclusion is unchanged over a range
of values then you have your answer. If the exact value of r makes an
important difference then you are a bit stuck unless you can persuade
any of the authors to supply their r value.

Michael

On 30/01/2022 22:46, Martin Lobo wrote:
> thanks wolfgang, the problem is that I don't get the correlation coefficients. Would it be valid to perform the meta-analysis with the post-treatment values and perform a meta-regression using the pre-treatment value as a covariate to assess whether the result is maintained regardless of the baseline value?
> best reagards
>
>
>
>
> Lorenzo Martín Lobo MTSAC, FACC, FESC
> Especialista Jerarquizado en Cardiología
> Jefe de Dpto Enf. Cardiovasculares y Cardiometabolismo Hospital Militar Campo de Mayo.
> Jefe de Cardiología Hospital Militar Campo de Mayo
> Ex Jefe de Unidad Coronaria Hospital Militar Campo de Mayo
> Miembro Titular de la Sociedad Argentina de Cardiología
> Fellow American College of Cardiology
> Fellow European Society of Cardiology
> Ex Miembro del Area de Investigación de la SAC
> Ex Director del Consejo de Aterosclerosis y Trombosis de la SAC
> Miembro Asesor del Consejo de Aterosclerosis y Trombosis de la SAC
> Ex Director del Consejo de Epidemiología y Prevención Cardiovascular de la SAC
>
> Miembro Asesor del Consejo de Epidemiología y Prevención Cardiovascular de la SAC
>
>
> Experto en Lipidos de la Sociedad Argentina de Lipidos.
> Miembro de la Sociedad Argentina de Lipidos.
> Instructor de ACLS de la American Heart Association
>
>
> ________________________________
> De: Viechtbauer, Wolfgang (SP) <wolfgang.viechtbauer using maastrichtuniversity.nl>
> Enviado: domingo, 30 de enero de 2022 12:27
> Para: Martin Lobo <mlobo4370 using hotmail.com>; r-sig-meta-analysis using r-project.org <r-sig-meta-analysis using r-project.org>
> Asunto: RE: [R-meta] Meta-analysis of mean differences
>
> Dear Lorenzo,
>
> This is relevant:
>
> https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.metafor-project.org%2Fdoku.php%2Fanalyses%3Amorris2008&data=04%7C01%7C%7C917452bf7fa649f2762508d9e4b12212%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637792271704657168%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=mpX54JCpJmlPXjt1nA9ThhqAizRVr0Vb15QCoS5c1vI%3D&reserved=0
>
> Best,
> Wolfgang
>
>> -----Original Message-----
>> From: R-sig-meta-analysis [mailto:r-sig-meta-analysis-bounces using r-project.org] On
>> Behalf Of Martin Lobo
>> Sent: Friday, 28 January, 2022 15:40
>> To: Dr. Gerta Rücker; r-sig-meta-analysis using r-project.org
>> Subject: [R-meta] Meta-analysis of mean differences
>>
>> Hi all. How should I do a meta-analysis of mean differences having the initial
>> and final values with their standard deviations for each group. With the metacont
>> function I can only put mean 1, standard deviation 1 mean 1 and standard
>> deviation 2 with their respective n.
>>
>> I think I should use a meta analysis of score changes but I don't know how to do
>> it in R.
>>
>> regards
>>
>> Lorenzo Martín Lobo MTSAC, FACC, FESC
>> Especialista Jerarquizado en Cardiología
>> Jefe de Dpto Enf. Cardiovasculares y Cardiometabolismo Hospital Militar Campo de
>> Mayo.
>> Jefe de Cardiología Hospital Militar Campo de Mayo
>> Ex Jefe de Unidad Coronaria Hospital Militar Campo de Mayo
>> Miembro Titular de la Sociedad Argentina de Cardiología
>> Fellow American College of Cardiology
>> Fellow European Society of Cardiology
>> Ex Miembro del Area de Investigación de la SAC
>> Ex Director del Consejo de Aterosclerosis y Trombosis de la SAC
>> Miembro Asesor del Consejo de Aterosclerosis y Trombosis de la SAC
>> Ex Director del Consejo de Epidemiología y Prevención Cardiovascular de la SAC
>>
>> Miembro Asesor del Consejo de Epidemiología y Prevención Cardiovascular de la SAC
>>
>> Experto en Lipidos de la Sociedad Argentina de Lipidos.
>> Miembro de la Sociedad Argentina de Lipidos.
>> Instructor de ACLS de la American Heart Association
>
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--
Michael
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