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Re: st: Trend test in meta analysis


From   "Tom Trikalinos" <ttrikalin@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Trend test in meta analysis
Date   Fri, 21 Dec 2007 16:59:46 -0500

Hi vijay

I'm not clear what form your data have.

Let me say right off the bat that such a question (dose-response)
could be evaluated on a qualitative basis (with a plot) without giving
a p-value. This should not be discarded as an option, given the strong
assumptions that are inherent in the data-abstraction process during
meta-analysis.

That being said see if the paper by Jesse Berlin et al.
"Meta-analysis of epidemiologic dose-response data." Epidemiology.
1993 May;4(3):218-28. PMID: 8512986 helps.

Two general comments
A.  first summing up the ORs 1 to 10 and then seeing for a trend (e.g.
with a meta-regression) is subject to Simpson's paradox. This is why
you need an approach like the on described in the cited paper.

B.  I'm not sure how metap could help you.  -metap- does a
meta-analysis of significance levels, a whole family of non-parametric
meta-analysis methods (metap implements 3 of numerous approaches).
This is essentially an omnibus test and therefore does not have the
interpretation you would wish. A meta-analysis of p-values asks is
there evidence of significant deviation from the null in AT LEAST ONE
of the studies?  A typical misinterpretaion of metap results is that
this is the p-value for the overall summary effect.


hope these thoughts help

tom



On Dec 21, 2007 3:52 PM, Jayaprakash, Vijay
<Vijay.Jayaprakash@roswellpark.org> wrote:
> Hi Stata users,
>        I'm trying to do a meta analysis of data from 10 different studies. The smoking variable in each study is stratified into categories (Category 1:1-10 cigarettes, Category 2: 10-20 cigs, Category3: 20-30 cigs etc.). I calculated the OR for each category (of smoking) by study.  I then did a meta analysis and calculated the OR for each category by random effects model using the meta command:
> meta  or1 lcl1 ucl1, ci eform
> meta  or2 lcl2 ucl2, ci eform
>
> I found that metap command can provide the p-value for each category (from p-values of each study for that specific category). Is there a way to get the p for trend BETWEEN the categories from the random effects estimate? I would like to report from the meta-analysis results if there is a dose-response relationship of smoking to the disease and if so what the p for trend is.
>
> I will very much appreciate your help.
>
> Thanks
>
> Vijay
>
>
>
>
>
>
>
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