[R-meta] Assessing publication bias from multilevel modelling

[James Pustejovsky]

I think regtest() is appropriate only for effect sizes that are
statistically independent. It would not be appropriate for Celiia's case,
where there is dependence among multiple effects from a given study.

Egger's regression test can be conducted simply by using the standard
errors of the effect size estimates (i.e., the "sei") as a predictor in a
meta-regression. Using cluster-robust variance estimation with this
meta-regression will take care of the dependence issue. A significant
coefficient on the standard error predictor would indicate funnel plot
asymmetry. (Although as always, a lack of statistically significance does
not *prove* that the funnel plot is symmetric.) When I've used this
technique, I fit the meta-regression without any random effects in the
model so that larger studies are given relatively more weight for
estimating the meta-regression coefficients.

The Henmi-Copas model is limited to univariate models. I don't know of a
way to generalize it for multi-variate meta-analysis.

James

On Wed, Feb 14, 2018 at 11:21 AM, Michael Dewey <lists at dewey.myzen.co.uk>
wrote:

> Dear Célia
>
> As far as I can see regtest can accept the yi, vi or sei parameters so you
> should be OK there. I do not think the HC method is going to be easy to do
> if it is even possible.
>
> Michael
>
>
> On 14/02/2018 16:14, Célia Sofia Moreira wrote:
>
>> Hi!
>>
>> I am studying a pretest-posttest controlled design and I'm using metafor
>> and clubSandwich packages. In some papers, I collected more than one
>> effect
>> size (from the same study sample). For this reason, I did multilevel
>> modelling using rma.mv function, with
>> random = ~ 1 |Study, struct = "UN".
>>
>> I would like to perform a publication bias analysis, using funnel plots,
>> tests for funnel plots asymmetry, and Hemni and copas (HC) model. However,
>> since I am using rma.mv function, I can only depict (multilevel) funnel
>> plots; unfortunately, tests for funnel plots asymmetry and HC model are
>> not
>> available for rma.mv....
>>
>> Do you know any alternative way to test the asymmetry of my "multilevel"
>> funnel plots, as well as to compare with the HC modelling?
>>
>> If not, can anybody please suggest other methods to assess publication
>> bias
>> in this multilevel case?
>>
>> Thank you very much,
>> celia
>>
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>>
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>>
> --
> Michael
> http://www.dewey.myzen.co.uk/home.html
>
>
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