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920 lines
32 KiB
Plaintext
{smcl}
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{* 7Jul2008}{...}
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{hline}
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help for {hi:metan}, {hi:labbe}
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{hline}
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{title:Fixed and random effects meta-analysis}
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{p 8 12 2}
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{cmd:metan}
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{it:varlist}
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[{cmd:if} {it:exp}]
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[{cmd:in} {it:range}]
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[{it:weight}]
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[{cmd:,}
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{it:measure_and_model_options}
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{it:options_for_continuous_data}
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{it:output_options}
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{it:forest_plot_options}
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]
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{p 12 12 2}
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where {it:measure_and_model_options} may be
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{p 12 12 2}
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{cmd:or}
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{cmd:rr}
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{cmd:rd}
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{cmd:fixed}
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{cmd:random}
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{cmd:fixedi}
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{cmd:peto}
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{cmd:cornfield}
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{cmd:chi2}
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{cmd:breslow}
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{cmdab:noint:eger}
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{cmd:cc(}{it:#}{cmd:)}
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{cmd:wgt(}{it:weightvar}{cmd:)}
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{cmd:second(}{it:model} or {it:estimates and description}{cmd:)}
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{cmd:first(}{it:estimates and description}{cmd:)}
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{p 12 12 2}
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and where {it:options_for_continuous_data} may be
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{p 12 12 2}
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{cmd:cohen}
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{cmd:hedges}
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{cmd:glass}
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{cmd:nostandard}
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{cmd:fixed}
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{cmd:random}
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{p 12 12 2}
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and where {it:output_options} may be
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{p 12 12 2}
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{cmd:by(}{it:byvar}{cmd:)}
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{cmd:nosubgroup}
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{cmd:sgweight}
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{cmd:log}
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{cmd:eform}
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{cmd:efficacy}
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{cmdab:il:evel(}{it:#}{cmd:)}
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{cmdab:ol:evel(}{it:#}{cmd:)}
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{cmd:sortby(}{it:varlist}{cmd:)}
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{cmd:label(}{it:namevar yearvar}{cmd:)}
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{cmd:nokeep}
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{cmd:notable}
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{cmd:nograph}
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{cmd:nosecsub}
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{p 12 12 2}
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and where {it:forest_plot_options} may be
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{p 12 12 2}
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{cmd:legend(}{it:string}{cmd:)}
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{cmdab:xla:bel(}{it:#},...{cmd:)}
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{cmdab:xt:ick(}{it:#},...{cmd:)}
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{cmd:boxsca(}{it:#}{cmd:)}
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{cmd:nobox}
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{cmd:nooverall}
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{cmd:nowt}
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{cmd:nostats}
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{cmd:group1(}{it:string}{cmd:)}
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{cmd:group2(}{it:string}{cmd:)}
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{cmd:effect(}{it:string}{cmd:)}
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{cmd:force}
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{p 12 12 2}
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...with further {it:forest_plot_options} in the version 9 update
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{p 12 12 2}
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{cmd:lcols(}{it:varlist}{cmd:)}
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{cmd:rcols(}{it:varlist}{cmd:)}
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{cmd:astext(}{it:#}{cmd:)}
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{cmd:double}
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{cmd:nohet}
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{cmd:summaryonly}
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{cmd:rfdist}
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{cmdab:rfl:evel(}{it:#}{cmd:)}
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{cmd:null(}{it:#}{cmd:)}
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{cmd:nulloff}
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{cmd:favours(}{it:string} # {it:string}{cmd:)}
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{cmd:firststats(}{it:string}{cmd:)}
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{cmd:secondstats(}{it:string}{cmd:)}
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{cmd:boxopt(}{it:}{cmd:)}
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{cmd:diamopt(}{it:}{cmd:)}
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{cmd:pointopt(}{it:}{cmd:)}
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{cmd:ciopt(}{it:}{cmd:)}
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{cmd:olineopt(}{it:}{cmd:)}
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{cmd:classic}
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{cmd:nowarning}
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{cmd:dp(}{it:#}{cmd:)}
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{it:graph_options}
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{p 8 12 2}
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{cmd:labbe}
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{it:varlist}
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[{cmd:if} {it:exp}]
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[{cmd:in} {it:range}]
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[{it:weight}]
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[{cmd:,}
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{cmd:nowt}
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{cmdab:per:cent}
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{cmd:or(}{it:#}{cmd:)}
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{cmd:rr(}{it:#}{cmd:)}
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{cmd:rd(}{it:#}{cmd:)}
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{cmd:null}
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{cmd:logit}
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{cmd:wgt(}{it:weightvar}{cmd:)}
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{cmd:symbol(}{it:symbolstyle}{cmd:)}
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{cmd:nolegend}
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{cmd:id(}{it:idvar}{cmd:)}
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{cmd:textsize(}{it:#}{cmd:)}
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{cmd:clockvar(}{it:clockvar}{cmd:)}
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{cmd:gap(}{it:#}{cmd:)}
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{it:graph_options}
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{title:Description}
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{p 4 4 2}
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These routines provide facilities to conduct meta-analyses of data from
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more than one study and to graph the results. Either binary (event) or
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continuous data from two groups may be combined using the {cmd:metan}
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command. Additionally, intervention effect estimates with corresponding
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standard errors or confidence intervals may be meta-analysed. Several
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meta-analytic methods are available, and the results may be displayed
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graphically in a Forest plot. A test of whether
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the summary effect measure is equal to the null is given,
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as well as a test for heterogeneity, i.e., whether the true effect in all
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studies is the same. Heterogeneity is also quantified using the I-squared
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measure (Higgins et al 2003).
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{p 4 4 2}
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{cmd:metan} (the main meta-analysis routine) requires either two, three, four
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or six variables to be declared. When four variables are specified
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these correspond to the number of events and non-events in the experimental group
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followed by those of the control group, and
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analysis of binary data is performed on the 2x2 table.
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With six variables, the data are assumed
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continuous and to be the sample size, mean and standard deviation of
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the experimental group followed by those of the control group.
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If three variables are specified these are assumed to be the effect estimate and
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its lower and upper confidence interval, and it is suggested that these are
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log transformed for odds ratios or risk ratios and the {cmd: eform} option used.
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If two variables are specified these are assumed to be the effect estimate and standard
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error; again, it is recommended that odds ratios or risk ratios are log transformed.
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{p 4 4 2}
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{cmd:labbe} draws a L'Abbe plot for event data (proportion of successes in the
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two groups). This is an alternative to the graph produced by {cmd:metan}.
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{p 4 4 2}
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{cmd:funnel} may be used for producing a "funnel plot", a graph of either the
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study sample size, standard error or precision (inverse of s.e.) against
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the effect size.
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{p 4 4 2}
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Note that the {cmd:metan} command now requires
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Stata version 9 and has been updated
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with several new options. Changes are mainly to graphics options which
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are collected in the section {it: Further options in the v9 update for metan: Forest plot},
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or otherwise marked {it:v9 update}. The previous version is still available under
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the name -metan7-
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{title:Remarks on funnel (discontinued)}
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{p 4 4 2}
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The {cmd:metafunnel} command has more options for
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funnel plots and version 8 graphics; as such {cmd:funnel} has been removed.
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See {help metafunnel} (if installed)
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{title:Options for metan}
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{dlgtab:Specifying the measure and model}
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{p 4 4 2}
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These options apply to binary data.
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{p 4 8 2}
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{cmd:rr} pools risk ratios (the default).
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{p 4 8 2}
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{cmd:or} pools odds ratios.
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{p 4 8 2}
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{cmd:rd} pools risk differences.
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{p 4 8 2}
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{cmd:fixed} specifies a fixed effect model using the method of
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Mantel and Haenszel (the default).
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{p 4 8 2}
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{cmd:fixedi} specifies a fixed effect model using the inverse variance method.
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{p 4 8 2}
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{cmd:peto} specifies that Peto's method is used to pool odds ratios.
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{p 4 8 2}
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{cmd:random} specifies a random effects model using the method of
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DerSimonian & Laird.
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{p 4 8 2}
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{cmd:cornfield} computes confidence intervals for odds ratios by method of
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Cornfield, rather than the (default) Woolf method.
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{p 4 8 2}
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{cmd:chi2} displays chi-squared statistic (instead of z) for the test
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of significance of the pooled effect size. This is available only for
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odds ratios pooled using Peto or Mantel-Haenszel methods.
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{p 4 8 2}
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{cmd:breslow} produces Breslow-Day test for homogeneity of ORs.
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{p 4 8 2}
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{cmd:cc(}{it:#}{cmd:)} defines a fixed continuity correction to add in the case where
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a study contains a zero cell. By default, {cmd:metan}
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adds 0.5 to each cell of a trial where a zero is encountered when
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using Inverse-Variance, Der-Simonian & Laird or Mantel-Haenszel
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weighting to enable finite variance estimators to be derived.
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However, the {cmd:cc()} option allows the use of other constants
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(including none). See also the {cmd:nointeger} option.
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{p 4 8 2}
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{cmd:nointeger} allows the cell counts to be non-integers. This may be useful
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when a variable continuity correction is sought for studies containing
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zero cells, but also may be used in other circumstances, such as where a
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cluster-randomised trial is to be incorporated and the "effective sample
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size" is less than the total number of observations.
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{p 4 8 2}
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{cmd:wgt(}{it:weightvar}{cmd:)} specifies alternative weighting
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for any data type. The effect size is to be computed by assigning
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a weight of {it:weightvar} to the studies. When RRs or ORs are declared,
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their logarithms are weighted. You should only use this option if you are
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satisfied that the weights are meaningful.
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{p 4 8 2}
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{cmd:second(}{it:model} or {it:estimates and description}{cmd:)} ({it:v9 update})
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A second analysis may be performed using another method, using {cmd:fixed},
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{cmd:random} or {cmd:peto}. Alternatively, the user may define their own
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estimate and 95% CI based on calculations performed externally to {cmd:metan},
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along with a description of their method, in the format
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{it: es lci uci description}. The results of this analysis are then displayed
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in the table and forest plot. Note that if {cmd:by} is used then sub-estimates
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from the second method are not displayed with user defined estimates, for
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obvious reasons.
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{p 4 8 2}
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{cmd:first(}{it:estimates and description}{cmd:)} ({it:v9 update})
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Use of this command completely changes the way {cmd:metan} operates, as results
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are no longer based on any standard methods. The user defines their own
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estimate, 95% CI and description as in the above, and must supply their own
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weightings using {cmd:wgt(}{it:weightvar}{cmd:)} to control display of box sizes. Note
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that data must be supplied in the 2 or 3 variable syntax
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({it:theta se_theta} or {it:es lci uci}) and
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{cmd:by} may not be used used for obvious reasons.
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{dlgtab:Continuous data}
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{p 4 8 2}
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{cmd:cohen} pools standardised mean differences by the method of Cohen
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(the default).
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{p 4 8 2}
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{cmd:hedges} pools standardised mean differences by the method of Hedges.
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{p 4 8 2}
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{cmd:glass} pools standardised mean differences by the method of Glass.
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{p 4 8 2}
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{cmd:nostandard} pools unstandardised mean differences.
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{p 4 8 2}
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{cmd:fixed} specifies a fixed effect model using the inverse variance method
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(the default).
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{p 4 8 2}
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{cmd:random} specifies a random effects model using the DerSimonian & Laird
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method.
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{p 4 8 2}
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{cmd:nointeger} denotes that the number of observations in each arm does not
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need to be an integer. By default, the first and fourth variables specified
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(containing N_intervention and N_control respectively) may occasionally be
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non-integer (see entry for {cmd:nointeger} under binary data).
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{dlgtab:Output}
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{p 4 8 2}
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{cmd:by()} specifies that the meta-analysis is to be stratified
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according to the variable declared.
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{p 4 8 2}
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{cmd:sgweight} specifies that the display is to present the percentage
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weights within each subgroup separately. By default {cmd:metan} presents
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weights as a percentage of the overall total.
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{p 4 8 2}
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{cmd:log} reports the results on the log scale
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(valid for OR and RR analyses from raw data counts only).
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{p 4 8 2}
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{cmd:nosubgroup} indicates that no within-group results are to be
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presented. By default {cmd:metan} pools trials both within and across
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all studies.
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{p 4 8 2}
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{cmd:eform} exponentiates all effect sizes and confidence intervals
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(valid only when the input variables are log odds ratios or log
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hazard ratios with standard error or confidence intervals).
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{p 4 8 2}
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{cmd:efficacy} expresses results as the vaccine efficacy (the proportion
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of cases that would have been prevented in the placebo group that
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would have been prevented had they received the vaccination).
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Only available with odds ratios (OR) or risk ratios (RR).
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{p 4 8 2}
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{cmd:ilevel(}{it:#}{cmd:)} specifies the coverage (eg 90,95,99 percent) for the
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individual trial confidence intervals. Default: {cmd:$S_level}.
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{cmd:ilevel()} and {cmd:olevel()} need not be the same. See {help set level}.
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{p 4 8 2}
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{cmd:olevel(}{it:#}{cmd:)} specifies the coverage (eg 90,95,99 percent) for the
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overall (pooled) trial confidence intervals. Default: {cmd:$S_level}.
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{cmd:ilevel()} and {cmd:olevel()} need not be the same. See {help set level}.
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{p 4 8 2}
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{cmd:sortby(}{it:varlist}{cmd:)} sorts by variable(s) in {it:varlist}
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{p 4 8 2}
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{cmd:label([namevar=}{it:namevar}{cmd:], [yearvar=}{it:yearvar}{cmd:])}
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labels the data by its name, year or both. Either or both option/s
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may be left blank. For the table display the overall length of the
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label is restricted to 20 characters. The option {cmd:lcols()} will
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override this if invoked.
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{p 4 8 2}
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{cmd:nokeep} prevents the retention of study parameters in permanent
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variables (see saved results below).
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{p 4 8 2}
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{cmd:notable} prevents display of table of results.
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{p 4 8 2}
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{cmd:nograph} prevents display of graph.
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{p 4 8 2}
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{cmd:nosecsub} ({it:v9 update}) prevents the display of sub-estimates
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using the second method if {cmd:second()}
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is used. Note that this is invoked automatically with user-defined
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estimates.
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{dlgtab:Forest plot}
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{p 4 8 2}
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{cmd:effect()} may be used when the effect size and its standard error
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are declared. This allows the graph to name the summary statistic used.
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{p 4 8 2}
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{cmd:nooverall} revents display of overall effect size on graph
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(automatically enforces the {cmd:nowt} option).
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{p 4 8 2}
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{cmd:nowt} prevents display of study weight on the graph.
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{p 4 8 2}
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{cmd:nostats} prevents display of study statistics on graph.
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{p 4 8 2}
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{cmd:counts} ({it:v9 update}) displays data counts (n/N) for each group when using
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binary data, or the sample size, mean and SD for each group if mean
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differences are used (the latter is a new feature).
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{p 4 8 2}
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{cmd:group1(}{it:string}{cmd:)}, {cmd:group2(}{it:string}{cmd:)} may be
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used with the {cmd:counts} option: the text should contain the
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names of the two groups.
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{p 4 8 2}
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{cmd:xlabel()} ({it:v9 update}) defines x-axis labels. This has been modified
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so that any number of points may defined. Also, there are no
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longer any checks made as to whether these points are sensible, so the
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user may define anything if the {cmd:force} option is used. Points must
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be comma separated.
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{p 4 8 2}
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{cmd:xtick()} adds tick marks to the x-axis. Points must
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be comma separated.
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{p 4 8 2}
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{cmd:force} forces the x-axis scale to be in the range specified
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by {cmd:xlabel()}.
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{p 4 8 2}
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{cmd:boxsca()} ({it:v9 update}) controls box scaling.
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This has been modified slightly so that the default is 100 (as in a
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percentage) and may be increased or decreased as such (e.g., 80 or 120 for
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20% smaller or larger respectively)
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{p 4 8 2}
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{cmd:nobox} prevents a "weighted box" being drawn for each study
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and markers for point estimates only are shown.
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{p 4 8 2}
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{cmd:texts()} ({it:v9 update}) specifies font size for text display on graph.
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This has been modified slightly so that the default is 100 (as in a
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percentage) and may be increased or decreased as such (e.g., 80 or 120 for
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20% smaller or larger respectively)
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{dlgtab:Further options for the forest plot in the v9 update}
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{p 4 8 2}
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{cmd:lcols(}{it:varlist}{cmd:)}, {cmd:rcols(}{it:varlist}{cmd:)}
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define columns of additional data to
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the left or right of the graph. The first two columns on the right are
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automatically set to effect size and weight, unless suppressed using
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the options {cmd:nostats} and {cmd:nowt}. If {cmd:counts} is used this
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will be set as the third column. {cmd:textsize()} can be used to fine-tune
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the size of the text in order to acheive a satisfactory appearance.
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The columns are labelled with the variable label, or the variable name
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if this is not defined. The first variable specified in {cmd:lcols()} is assumed to be
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the study identifier and this is used in the table output.
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{p 4 8 2}
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{cmd:astext(}{it:#}{cmd:)}
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specifies the percentage of the graph to be taken up by text.
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The default is 50 and the percentage must be in the range 10-90.
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{p 4 8 2}
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{cmd:double}
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allows variables specified in {cmd:lcols} and {cmd:rcols} to run over two
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lines in the plot. This may be of use if long strings are to be used.
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{p 4 8 2}
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{cmd:nohet}
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prevents display of heterogeneity statistics in the graph.
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{p 4 8 2}
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{cmd:summaryonly}
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shows only summary estimates in the graph (may be of use for multiple
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subgroup analyses)
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{p 4 8 2}
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{cmd:rfdist}
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displays the confidence interval of the approximate predictive
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distribution of a future trial, based on the extent of heterogeneity.
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This incorporates uncertainty in the location and spread of the random
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effects distribution using the formula {cmd: t(df) x sqrt(se2 + tau2)}
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where t is the t-distribution with k-2 degrees of freedom, se2 is the
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squared standard error and tau2 the heterogeneity statistic.
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The CI is then displayed with lines extending from the diamond. Note that
|
|
with <3 studies the distribution is inestimable and effectively infinite, thus
|
|
displayed with dotted lines, and where heterogeneity is zero there is still
|
|
a slight extension as the t-statistic is always greater than the corresponding
|
|
normal deviate. For further information see Higgins JPT, Thompson SG (2006)
|
|
|
|
{p 4 8 2}
|
|
{cmd:rflevel(}{it:#}{cmd:)} specifies the coverage (eg 90,95,99 percent) for the
|
|
confidence interval of the predictive distribution. Default: {cmd:$S_level}.
|
|
See {help set level}.
|
|
|
|
{p 4 8 2}
|
|
{cmd:null(}{it:#}{cmd:)}
|
|
displays the null line at a user-defined value rather than 0 or 1.
|
|
|
|
{p 4 8 2}
|
|
{cmd:nulloff}
|
|
removes the null hypothesis line from the graph
|
|
|
|
{p 4 8 2}
|
|
{cmd:favours(}{it:string} # {it:string}{cmd:)}
|
|
applies a label saying something about the treatment effect to either
|
|
side of the graph (strings are separated by the # symbol). This replaces
|
|
the feature available in {cmd:b1title} in the previous version of metan.
|
|
|
|
{p 4 8 2}
|
|
{cmd:firststats(}{it:string}{cmd:)}, {cmd:secondstats(}{it:string}{cmd:)}
|
|
labels overall user-defined estimates when these have been specified.
|
|
Labels are displayed in the position usually given to the heterogeneity
|
|
statistics.
|
|
|
|
{p 4 8 2}
|
|
{cmd:boxopt()}, {cmd:diamopt()}, {cmd:pointopt()}, {cmd:ciopt()}, {cmd:olineopt()}
|
|
specify options for the graph routines within the program, allowing the
|
|
user to alter the appearance of the graph. Any options associated with a
|
|
particular graph command may be used, except some that would cause incorrect
|
|
graph appearance. For example, diamonds are plotted using the {help twoway pcspike}
|
|
command, so options for line styles are available (see {help line options});
|
|
however, altering the x-y
|
|
orientation with the option {cmd:horizontal} or {cmd:vertical} is not
|
|
allowed. So, {cmd:diamopt(lcolor(green) lwidth(thick))} feeds into a command
|
|
such as {cmd:pcspike(y1 x1 y2 x2, lcolor(green) lwidth(thick))}
|
|
|
|
{p 8 8 2}
|
|
{cmd:boxopt()} controls the boxes and uses options for a weighted marker
|
|
(e.g., shape, colour; but not size). See {help marker options}
|
|
|
|
{p 8 8 2}
|
|
{cmd:diamopt()} controls the diamonds and uses options for pcspike (not horizontal/vertical).
|
|
See {help line options}
|
|
|
|
{p 8 8 2}
|
|
{cmd:pointopt()} controls the point estimate using marker options.
|
|
See {help marker options} and {help marker label options}
|
|
|
|
{p 8 8 2}
|
|
{cmd:ciopt()} controls the confidence intervals for studies using options
|
|
for pcspike (not horizontal/vertical). See {help line options}
|
|
|
|
{p 8 8 2}
|
|
{cmd:olineopt()} controls the overall effect line with options for an additional
|
|
line (not position). See {help line options}
|
|
|
|
{p 4 8 2}
|
|
{cmd:classic} specifies that solid black boxes without point estimate markers are used as
|
|
in the previous version of metan.
|
|
|
|
{p 4 8 2}
|
|
{cmd:nowarning} switches off the default display of a note warning that studies are
|
|
weighted from random effects anaylses.
|
|
|
|
{p 4 8 2}
|
|
{cmd:dp(}{it:#}{cmd:)} sets the number of decimal places that effect estimates are displayed with
|
|
(default is 2).
|
|
|
|
{p 4 8 2}
|
|
{it:graph_options}
|
|
specifies overall graph options that would appear at the end of a {cmd:twoway}
|
|
graph command. This allows the addition of titles, subtitles, captions etc.,
|
|
control of margins, plot regions, graph size, aspect ratio and the use of schemes.
|
|
As titles may be added in this way previous options {cmd:b2title} etc. are no
|
|
longer necessary. See {search graph options}
|
|
|
|
|
|
{title:Options for labbe}
|
|
|
|
{p 4 8 2}
|
|
{cmd:nowt} declares that the plotted data points are to be the same size.
|
|
|
|
{p 4 8 2}
|
|
{cmd:percent} displays the event rates as percentages rather than proportions.
|
|
|
|
{p 4 8 2}
|
|
{cmd:null} draws a line corresponding to a null effect (ie p1=p2).
|
|
|
|
{p 4 8 2}
|
|
{cmd:or(}{it:#}{cmd:)} draws a line corresponding to a fixed odds ratio of
|
|
{it:#}.
|
|
|
|
{p 4 8 2}
|
|
{cmd:rd(}{it:#}{cmd:)} draws a line corresponding to a fixed risk difference of
|
|
{it:#}.
|
|
|
|
{p 4 8 2}
|
|
{cmd:rr(}{it:#}{cmd:)} draws a line corresponding to a fixed risk ratio
|
|
of {it:#}. See also the {cmd:rrn()} option.
|
|
|
|
{p 4 8 2}
|
|
{cmd:rrn(}{it:#}{cmd:)} draws a line corresponding to a fixed risk ratio
|
|
(for the non-event) of {it:#}.
|
|
The {cmd:rr()} and {cmd:rrn()} options may require explanation.
|
|
Whereas the OR and RD are invariant to the definition of which of
|
|
the binary outcomes is the "event" and which is the "non-event",
|
|
the RR is not. That is, while the command {cmd:metan a b c d , or}
|
|
gives the same result as {cmd:metan b a d c , or} (with direction
|
|
changed), an RR analysis does not. The L'Abbe plot allows the display
|
|
of either or both to be superimposed risk difference.
|
|
|
|
{p 4 8 2}
|
|
{cmd:logit} is for use with the {cmd:or()} option; it displays the
|
|
probabilities on the logit scale ie log(p/1-p). On the logit scale the
|
|
odds ratio is a linear effect, and so this makes it easier to assess the
|
|
"fit" of the line.
|
|
|
|
{p 4 8 2}
|
|
{cmd:wgt(}{it:weightvar}{cmd:)} specifies alternative weighting by the specified variable
|
|
(default is sample size).
|
|
|
|
{p 4 8 2}
|
|
{cmd:symbol(}{it:symbolstyle}{cmd:)} allows the symbol to be changed (see help {help symbolstyle}) the
|
|
default being hollow circles (or points if weights are not used).
|
|
|
|
{p 4 8 2}
|
|
{cmd:nolegend} suppresses a legend being displayed (the default if more than one
|
|
line corresponding to effect measures are specified).
|
|
|
|
{p 4 8 2}
|
|
{cmd:id(}{it:idvar}{cmd:)} displays marker labels with the specified ID variable {it:idvar}.
|
|
{cmd:clockvar()} and {cmd:gap()} may be used to fine-tune the display, which may become
|
|
unreadable if studies are clustered together in the graph.
|
|
|
|
{p 4 8 2}
|
|
{cmd:textsize(}{it:#}{cmd:)} increases or decreases the text size of the id label by specifying
|
|
{it:#} to be more or less than unity. The default is usually satisfactory, but may need to be adjusted.
|
|
|
|
{p 4 8 2}
|
|
{cmd:clockvar(}{it:clockvar}{cmd:)} specifies the position of {it:idvar} around the
|
|
study point, as if it were a clock face (values must be integers- see {help clockposstyle}).
|
|
This may be used to organise labels where studies are clustered together. By default, labels are positioned
|
|
to the left (9 o'clock) if above the null and to the right (3 o'clock) if below. Missing values
|
|
in {it:clockvar} will be assigned the default position, so this need not be specified for all observations.
|
|
|
|
{p 4 8 2}
|
|
{cmd:gap(}{it:#}{cmd:)} increases or decreases the gap between the study marker and the id label by specifying
|
|
{it:#} to be more or less than unity. The default is usually satisfactory, but may need to be adjusted.
|
|
|
|
{p 4 8 2}
|
|
{it:graph_options} are options for Stata 8 graphs (see help on {help graph}).
|
|
|
|
|
|
{title:Remarks on metan}
|
|
|
|
{p 4 4 2}
|
|
For two or three variables, a variance-weighted analysis is performed in
|
|
a similar fashion to the {help meta} command; the two variable syntax
|
|
is {it:theta} and {it:SE(theta)}. The 3 variable syntax is {it:theta},
|
|
{it:lower ci (theta)}, {it:upper ci (theta)}. Note that in this situation
|
|
"{it:theta}" is taken to be the logarithm of the effect size if the odds
|
|
ratio or risk ratio is used. {hi:This differs from the equivalent in the {cmd:meta} command}.
|
|
This program does not assume the three variables need log transformation:
|
|
if odds ratios or risk ratios are combined, it is up to the user to
|
|
log-transform them first. The {cmd:eform} option may be used to change
|
|
back to the original scale if needed. By default the confidence
|
|
intervals are assumed symmetric, and the studies are pooled by taking
|
|
the variance to be equal to (CI width)/2z.
|
|
|
|
{p 4 4 2}
|
|
Note that for graphs on the log scale (that is, ORs or RRs), values
|
|
outside the range [10e-8,10e8] are not displayed, and similarly graphs of
|
|
other measures (log ORs, RDs, SMDs) are restricted to the range [-10e8,10e8].
|
|
A confidence interval which extends beyond this, or the specified scale
|
|
if {cmd:force} is used, will have an arrow added at the end of the range.
|
|
|
|
{p 4 4 2}
|
|
{hi: Further notes on v9 update:} If {cmd:by} is used with a string variable the
|
|
stratification variable is not sorted alpha-numerically and the original
|
|
order that the groups appear in the data is preserved. This may be of use if
|
|
a particular display order is required; if not, {cmd:sortby} may be used.
|
|
The option {cmd:counts} is now available for continuous data and displays
|
|
sample size, mean and SD in each group. The estimate for heterogeneity between
|
|
groups from a stratified analysis using the Mantel-Haenszel method, and
|
|
arguably the Peto method, is invalid. Therefore this is not displayed in the
|
|
output for either of these methods.
|
|
|
|
{p 4 4 2}
|
|
Note that there is a small add-on program to calculate the confidence interval for
|
|
the I-squared statistic- type {cmd:i2ci} after running metan. This uses the method
|
|
described by Higgins & Thompson (2002), Appendix A2.
|
|
|
|
|
|
{title:Remarks on labbe}
|
|
|
|
{p 4 4 2}
|
|
By default the size of the plotting symbol is proportional to the sample
|
|
size of the study. If weights are specified the plotting size will be
|
|
proportional to the weight variable. Note that {cmd:labbe} has now been updated to version 8 graphics.
|
|
All options work the same as in the previous version, and some minor graphics options have been added.
|
|
|
|
|
|
|
|
{title:Stored}
|
|
|
|
By default, {cmd:metan} adds the following new variables to the data set:
|
|
|
|
_ES Effect size (ES)
|
|
_seES Standard error of ES
|
|
or, when OR or RR are specfied:
|
|
_selogES the standard error of its logarithm
|
|
_LCI Lower confidence limit for ES
|
|
_UCI Upper confidence limit for ES
|
|
_WT Study percentage weight
|
|
_SS Study sample size
|
|
|
|
|
|
{title:Examples}
|
|
|
|
{p 4 8 2}
|
|
All examples use a simulated example dataset (Ross Harris 2006)
|
|
|
|
{p 8 12 2}
|
|
{stata "use http://fmwww.bc.edu/repec/bocode/m/metan_example_data":. use http://fmwww.bc.edu/repec/bocode/m/metan_example_data}
|
|
|
|
{p 4 8 2}
|
|
Risk difference from raw cell counts, random effects model, "label" specification with counts displayed
|
|
|
|
{p 8 12 2}
|
|
{cmd:. metan tdeath tnodeath cdeath cnodeath, }
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{cmd:rd random label(namevar=id, yearid=year) counts}
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{it:({stata "metan_examples metan_example_basic":click to run})}
|
|
|
|
{p 4 8 2}
|
|
Sort by year, use data columns syntax. Text size increased, specify percentage of graph as text and
|
|
two lines per study; suppress stats, weight, heterogeneity stats and table.
|
|
|
|
|
|
{p 8 12 2}
|
|
{cmd:. metan tdeath tnodeath cdeath cnodeath, }
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{cmd:sortby(year) lcols(id year country) rcols (population) }
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{cmd:textsize(110) astext(60) double nostats nowt nohet notable}
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{it:({stata "metan_examples metan_example_cols":click to run})}
|
|
|
|
{p 4 8 2}
|
|
Analyse continuous data (6 parameter syntax), stratify by type of study, with weights summing to 100 within sub group,
|
|
second analysis specified, display random effects distribution, show raw data counts, display
|
|
"favours treatment vs. favours control" labels
|
|
|
|
{p 8 12 2}
|
|
{cmd:. metan tsample tmean tsd csample cmean csd, }
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{cmd:by(type_study) sgweight fixed second(random) rfdist }
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{cmd:counts label(namevar = id) }
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{cmd:favours(Treatment reduces blood pressure # Treatment increases blood pressure)}
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{it:({stata "metan_examples metan_example_by":click to run})}
|
|
|
|
{p 4 8 2}
|
|
Generate log odds ratio and standard error, analyse with 2 parameter syntax. Graph has exponential form,
|
|
scale is forced within set limits and ticks added, effect label specified.
|
|
|
|
{p 8 12 2}
|
|
{cmd:. gen logor = ln( (tdeath*cnodeath)/(tnodeath*cdeath) )}
|
|
|
|
{p 8 12 2}
|
|
{cmd:. gen selogor = sqrt( (1/tdeath) + (1/tnodeath) + (1/cdeath) + (1/cnodeath) )}
|
|
|
|
{p 8 12 2}
|
|
{cmd:. metan logor selogor, eform xlabel(0.5, 1, 1.5, 2, 2.5) }
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{cmd:force xtick(0.75, 1.25, 1.75, 2.25) effect(Odds ratio)}
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{it:({stata "metan_examples metan_example_2param":click to run})}
|
|
|
|
{p 4 8 2}
|
|
Display diagnostic test data with 3 parameter syntax. Weight is number of positive diagnoses, axis label set
|
|
and null specified at 50%. Overall effect estimate is not displayed, graph for visual examination only.
|
|
|
|
{p 8 12 2}
|
|
{cmd:. metan percent lowerci upperci, wgt(n_positives) }
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{cmd:xlabel(0,10,20,30,40,50,60,70,80,90,100) force }
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{cmd:null(50) label(namevar=id) nooverall notable }
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{cmd:title(Sensitivity, position(6))}
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{it:({stata "metan_examples metan_example_diag":click to run})}
|
|
|
|
{p 4 8 2}
|
|
User has analysed data with a non-standard technique and supplied effect estimates, weights and description of statistics.
|
|
The scheme "Economist" has been used.
|
|
|
|
{p 8 12 2}
|
|
{cmd:. metan OR ORlci ORuci, wgt(bweight) }
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{cmd:first(0.924 0.753 1.095 Bayesian) }
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{cmd:firststats(param V=3.86, p=0.012) }
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{cmd:label(namevar=id) }
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{cmd:xlabel(0.25, 0.5, 1, 2, 4) force }
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{cmd:null(1) aspect(1.2) scheme(economist)}
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{it:({stata "metan_examples metan_example_user":click to run})}
|
|
|
|
{p 4 8 2}
|
|
Variable "counts" defined showing raw data. Options to change the box, effect estimate marker and confidence interval used,
|
|
and the counts variable has been attached to the estimate marker as a label.
|
|
|
|
{p 8 12 2}
|
|
{cmd:. gen counts = ". " + string(tdeath) + "/" + string(tdeath+tnodeath) }
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{cmd:+ ", " + string(cdeath) + "/" + string(cdeath+cnodeath)}
|
|
|
|
{p 8 12 2}
|
|
{cmd: . metan tdeath tnodeath cdeath cnodeath, }
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{cmd:lcols(id year) notable }
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{cmd:boxopt( mcolor(forest_green) msymbol(triangle) ) }
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{cmd:pointopt( msymbol(triangle) mcolor(gold) msize(tiny) }
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{cmd:mlabel(counts) mlabsize(vsmall) mlabcolor(forest_green) mlabposition(1) ) }
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{cmd:ciopt( lcolor(sienna) lwidth(medium) )}
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{it:({stata "metan_examples metan_example_custom":click to run})}
|
|
|
|
{p 4 8 2}
|
|
L'Abbe plot with labelled axes and display of risk ratio and risk difference.
|
|
|
|
{p 8 12 2}
|
|
{cmd:. labbe tdeath tnodeath cdeath cnodeath, }
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{cmd:xlabel(0,0.25,0.5,0.75,1) ylabel(0,0.25,0.5,0.75,1) }
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{cmd:rr(1.029) rd(0.014) null}
|
|
{p_end}
|
|
{p 12 12 2}
|
|
{it:({stata "metan_examples labbe_example":click to run})}
|
|
|
|
|
|
|
|
{title:Authors}
|
|
|
|
{p 4 4 0}
|
|
Michael J Bradburn, Jonathan J Deeks, Douglas G Altman.
|
|
Centre for Statistics in Medicine, University of Oxford,
|
|
Wolfson College Annexe, Linton Road, Oxford, OX2 6UD, UK
|
|
|
|
{title:Version 9 update}
|
|
|
|
{p 4 4 0}
|
|
Ross J Harris, Roger M Harbord, Jonathan A C Sterne.
|
|
Department of Social Medicine, University of Bristol,
|
|
Canynge Hall, Whiteladies Road, Bristol BS8 2PR, UK
|
|
|
|
{title:Other updates and improvements to code and help file}
|
|
|
|
{p 4 4 0}
|
|
Patrick Royston. MRC Clinical Trials Unit, 222 Euston Road,
|
|
London, NW1 2DA
|
|
|
|
{title:Acknowledgements}
|
|
|
|
{p 4 4 0}
|
|
Thanks to Vince Wiggins, Kit Baum and Jeff Pitblado of Statacorp
|
|
who offered advice and helped facilitate the version 9 update.
|
|
Thanks also to all the people who helped with beta-testing and
|
|
made comments and suggested improvements.
|
|
|
|
{title:References}
|
|
|
|
{p 4 4 0}
|
|
Higgins JPT, Thompson SG, Deeks JJ,
|
|
Altman DG. Measuring inconsistency in meta-analyses. BMJ
|
|
2003; 327:557-560. {browse "http://dx.doi.org/10.1136/bmj.327.7414.557":http://dx.doi.org/10.1136/bmj.327.7414.557}
|
|
|
|
{p 4 4 0}
|
|
Higgins JPT, Thompson SG (2006) Presenting random effects meta-analyses:
|
|
where we are going wrong? (from presentation, work in preparation)
|
|
|
|
|
|
{title:Also see}
|
|
|
|
STB: STB-44 sbe24
|
|
On-line: help for {help metan7}, {help metannt}
|
|
{help meta} (if installed), {help metacum} (if installed),
|
|
{help metareg} (if installed), {help metabias} (if installed),
|
|
{help metatrim} (if installed), {help metainf} (if installed),
|
|
{help galbr} (if installed), {help metafunnel} (if installed)
|
|
|