st: metan and other meta-analysis commands in Stata

[Jonathan Sterne <Jonathan.Sterne@bristol.ac.uk>]

Following the recent posting of an updated metan command on the SSC 
archive, Austin Nichols <austinnichols@gmail.com> commented:


> I for one would much appreciate a comparison of the various
> user-written packages for meta-analysis included in the help file, as
> a supplement to "Also see" section at the bottom of the help file.
We are currently writing Stata Journal articles on the new metan command 
and other new or updated Stata meta-analysis commands. The following is an 
attempt to summarise the facilities of some (though not all) of the 
user-written commands for meta-analysis in Stata.

1. The meta command
This was the first Stata meta-analysis command. It requires the user to 
supply the treatment effect estimate and its standard error for each study. 
It uses inverse-variance weighting to derive fixed- and random-effects 
summary estimates of the treatment effect estimate.

The meta command has not been updated since 1998, and uses Stata 7 
graphics. As explained below, we now regard this command as redundant. We 
are considering releasing a new version of meta that acts as a wrapper for 
metan.

2. The metan command
The original version of the metan comand used as input the cell frequencies 
from the 2x2 table for each study (for binary outcomes) or the mean and 
standard deviation in each group (for numerical outcomes). It provides a 
comprehensive range of methods for meta-analysis, including 
inverse-variance weighted meta-analysis, and also creates new variables 
containing the the treatment effect estimate and its standard error for 
each study. These variables can then be used as input to a number of other 
Stata meta-analysis commands.

All the meta-analysis calculations available in metan are based on standard 
methods, an overview of which may be found in Chapter 15 ("Statistical 
methods for examining heterogeneity and combining results from several 
studies in meta-analysis", by Deeks, Altman and Bradburn), in Egger M, 
Davey Smith G, Altman DG, eds. Systematic reviews in health care: 
meta-analysis in context 2nd ed. London: BMJ Books, 2001."

The metan command has been updated on a number of occasions since it was 
originally released. Because it now allows the user to supply the treatment 
effect estimate and its standard error for each study, it now posesses 
(almost) all the functionality of the meta command. Somewhat confusingly, 
the release of metan that added this facility was made available on the SSC 
archive in a package called "metaaggr" (meta-analysis of aggregate data). 
This may have meant that some users continued with older versions of the 
command.

Other important new facilities added since the original metan command was 
released include the by() option to conduct meta-analyses in subgroups, and 
the recent update to Stata 9 graphics.

3. The metareg command
This command does meta-regression. It was released in 1998, with a major 
update made available on the SSC archive in 2004. It requires the user to 
input the the treatment effect estimate and its standard error for each 
study.

4. The metabias command
This command reports results of the Begg and Mazumdar (1994) and Egger et 
al. (1997) tests for funnel plot asymmetry. It also produces funnel plots 
and Galbraith plots, but these use Stata 7 graphics. It was released in 
1997 and updates have been made available on the SSC archive on a number of 
occasions since then. It requires the user to input the the treatment 
effect estimate and its standard error for each study.

5. The metafunnel command
This command displays funnel plots. It was released in 2004 and uses Stata 
8 graphics. It requires the user to input the the treatment effect estimate 
and its standard error for each study.

6. The metatrim command
This command implements the "trim and fill" method to adjust for 
publication bias in funnel plots. The most recent release was in 2003. It 
requires the user to input the the treatment effect estimate and its 
standard error for each study.

7. The metacum command.
This command performs cumulative meta-analyses, and graphs the results. It 
does this using repeat calls to the meta command. It was released in 1998, 
and has not been updated since then. It uses Stata 7 graphics.

Austin Nichols <austinnichols@gmail.com> also asked:


> Would the authors would be willing to add to the latest release? The
> help file available via view 
http://www.stata.com/stb/stb44/sbe24/metan.hlp
> is not as helpful as one might expect.  The syntax of the required
> varlist is unspecified, but must be inferred from the examples at the
> very end of the help file, e.g. metan n1 m1 sd1 n2 m2 sd2
Austin should ensure that he is looking at the most recent help file for 
metan, by typing -view http://fmwww.bc.edu/repec/bocode/m/metan.hlp- in 
Stata, or by installing the metan package (type -ssc install metan, 
replace- and then -help metan- in Stata). This provides a number of 
clickable examples of the use of the command. The required order of the 
variables is explained in the description of the command: "When four 
variables are specified these correspond to the number of events and 
non-events in the experimental group followed by those of the control 
group".

We hope that Statalist users will find this information helpful.

With best wishes

Jonathan Sterne, Ross Harris and Roger Harbord


----------------------

Jonathan Sterne

Department of Social Medicine
University of Bristol
Canynge Hall
Whiteladies Road
Bristol BS8 2PR
UK

Tel:    0117 928 7396
Fax:    0117 928 7325
E-mail: jonathan.sterne@bristol.ac.uk
web:    www.epi.bris.ac.uk/staff/jsterne.htm

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