trimfill {meta}R Documentation

Trim and fill method for meta-analysis

Description

Trim and fill method for estimating and adjusting for the number and outcomes of missing studies in a meta-analysis.

Usage

trimfill(x, seTE, left=NULL, ma.fixed=TRUE, type="L", n.iter.max=50,
         sm=NULL, studlab=NULL, level, level.comb, silent=TRUE)

Arguments

x An object of class meta, or estimated treatment effect in individual studies.
seTE Standard error of estimated treatment effect (mandatory if x not of class meta).
left A logical indicating whether studies are supposed to be missing on the left or right side of the funnel plot. If NULL, the linear regression test for funnel plot symmetry (i.e., function metabias(..., meth="linreg")) is used to determine whether trials are missing on the left or right side.
ma.fixed A logical indicating whether a fixed effect or random effects model is used to estimate the number of missing studies.
type A character indicating which method is used to estimate the number of missing studies. Either "L" or "R".
n.iter.max Maximum number of iterations to estimate number of missing studies.
sm An optional character string indicating underlying summary measure, e.g., "RD", "RR", "OR", "AS", "MD", "SMD"; ignored if x is of class meta.
studlab An optional vector with study labels; ignored if x is of class meta.
level The level used to calculate confidence intervals for individual studies. If existing, x$level is used as value for level; otherwise 0.95 is used.
level.comb The level used to calculate confidence interval for the pooled estimate. If existing, x$level.comb is used as value for level.comb; otherwise 0.95 is used.
silent A logical indicating whether basic information on iterations shown.

Details

The trim and fill method can be used for estimating and adjusting for the number and outcomes of missing studies in a meta-analysis. The method relies on scrutiny of one side of a funnel plot for asymmetry assumed due to publication bias.

The function metagen is called internally.

Value

An object of class c("metagen", "meta", "trimfill"). The object is a list containing the following components:

studlab, sm
left, ma.fixed As defined above.
type, n.iter.max
TE, seTE Estimated treatment effect and standard error of individual studies.
w.fixed, w.random Weight of individual studies (in fixed and random effects model).
TE.fixed, seTE.fixed Estimated overall treatment effect and standard error (fixed effect model).
TE.random, seTE.random Estimated overall treatment effect and standard error (random effects model).
k Number of studies combined in meta-analysis.
Q Heterogeneity statistic Q.
tau Square-root of between-study variance (moment estimator of DerSimonian-Laird).
method Pooling method: "Inverse".
call Function call.
n.iter Actual number of iterations to estimate number of missing studies.
trimfill A logical vector indicating studies that have been added by trim and fill method.
k0 Number of studies added by trim and fill.
level The level used to calculate confidence intervals for individual studies.
level.comb The level used to calculate confidence interval for the pooled estimate.

Author(s)

Guido Schwarzer sc@imbi.uni-freiburg.de

References

Duval S & Tweedie R (2000), A nonparametric "Trim and Fill" method of accounting for publication bias in meta-analysis. Journal of the American Statistical Association, 95, 89–98.

Duval S & Tweedie R (2000), Trim and Fill: A simple funnel-plot-based method of testing and adjusting for publication bias in meta-analysis. Biometrics, 56, 455–463.

See Also

metagen, metabias, funnel

Examples

data(Fleiss93)
meta1 <- metabin(event.e, n.e, event.c, n.c,
                 data=Fleiss93, sm="OR")
tf1 <- trimfill(meta1)
summary(tf1)
funnel(tf1, pch=ifelse(tf1$trimfill, 1, 16),
       level=0.95, comb.fixed=TRUE)

[Package meta version 0.9-18 Index]