Abstract
BackgroundSystematic reviews and meta-analyses of binary outcomes are widespread in all areas of application. The odds ratio, in particular, is by far the most popular effect measure. However, the standard meta-analysis of odds ratios using a random-effects model has a number of potential problems. An attractive alternative approach for the meta-analysis of binary outcomes uses a class of generalized linear mixed models (GLMMs). GLMMs are believed to overcome the problems of the standard random-effects model because they use a correct binomial-normal likelihood. However, this belief is based on theoretical considerations, and no sufficient simulations have assessed the performance of GLMMs in meta-analysis. This gap may be due to the computational complexity of these models and the resulting considerable time requirements.MethodsThe present study is the first to provide extensive simulations on the performance of four GLMM methods (models with fixed and random study effects and two conditional methods) for meta-analysis of odds ratios in comparison to the standard random effects model.ResultsIn our simulations, the hypergeometric-normal model provided less biased estimation of the heterogeneity variance than the standard random-effects meta-analysis using the restricted maximum likelihood (REML) estimation when the data were sparse, but the REML method performed similarly for the point estimation of the odds ratio, and better for the interval estimation.ConclusionsIt is difficult to recommend the use of GLMMs in the practice of meta-analysis. The problem of finding uniformly good methods of the meta-analysis for binary outcomes is still open.
Highlights
Systematic reviews and meta-analyses of binary outcomes are widespread in all areas of application
It makes the strong assumption that the estimated within-study variances σi2 can be used in place of the unknown true variances σi2, and it does not account for the correlation between the estimated within-study variances σi2 and the effect measures θi [3,4,5]
An attractive alternative approach for the meta-analysis of binary outcomes uses a class of generalized linear mixed models (GLMMs)
Summary
Systematic reviews and meta-analyses of binary outcomes are widespread in all areas of application. The standard meta-analysis of odds ratios using a random-effects model has a number of potential problems. GLMMs are believed to overcome the problems of the standard random-effects model because they use a correct binomial-normal likelihood. This belief is based on theoretical considerations, and no sufficient simulations have assessed the performance of GLMMs in meta-analysis. When the outcome of interest is a transformation of a binomial outcome such as the logit transformation, the standard random-effects model assumes that within-study variability can be described by an approximate normal likelihood, i.e. the estimates of effects θi ∼ N θi, σi in each study i, i = 1 . The standard REM suffers from transformation bias ([6]) and bias in the estimation of the random-effect variance τ 2
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