Institute of Medical Biometry and Medical Informatics, University Medical Center, 79104 Freiburg, Germany.
Biostatistics. 2011 Jan;12(1):122-42. doi: 10.1093/biostatistics/kxq046. Epub 2010 Jul 22.
Statistical heterogeneity and small-study effects are 2 major issues affecting the validity of meta-analysis. In this article, we introduce the concept of a limit meta-analysis, which leads to shrunken, empirical Bayes estimates of study effects after allowing for small-study effects. This in turn leads to 3 model-based adjusted pooled treatment-effect estimators and associated confidence intervals. We show how visualizing our estimators using the radial plot indicates how they can be calculated using existing software. The concept of limit meta-analysis also gives rise to a new measure of heterogeneity, termed G(2), for heterogeneity that remains after small-study effects are accounted for. In a simulation study with binary data and small-study effects, we compared our proposed estimators with those currently used together with a recent proposal by Moreno and others. Our criteria were bias, mean squared error (MSE), variance, and coverage of 95% confidence intervals. Only the estimators arising from the limit meta-analysis produced approximately unbiased treatment-effect estimates in the presence of small-study effects, while the MSE was acceptably small, provided that the number of studies in the meta-analysis was not less than 10. These limit meta-analysis estimators were also relatively robust against heterogeneity and one of them had a relatively small coverage error.
统计异质性和小样本效应是影响荟萃分析有效性的两个主要问题。在本文中,我们介绍了极限荟萃分析的概念,该方法允许小样本效应后,对研究效应进行收缩的经验贝叶斯估计。这反过来又导致了 3 种基于模型的调整后的汇总处理效果估计值和相关置信区间。我们展示了如何使用径向图可视化我们的估计值,以指示如何使用现有软件计算它们。极限荟萃分析的概念还产生了一种新的异质性度量,称为 G(2),用于在考虑小样本效应后剩余的异质性。在一项具有二项数据和小样本效应的模拟研究中,我们将我们提出的估计值与目前使用的估计值以及 Moreno 等人最近的建议进行了比较。我们的标准是偏倚、均方误差 (MSE)、方差和 95%置信区间的覆盖率。只有在存在小样本效应的情况下,来自极限荟萃分析的估计值才能产生近似无偏的处理效果估计值,而 MSE 可以接受较小,前提是荟萃分析中的研究数量不少于 10。这些极限荟萃分析估计值也相对稳健,不受异质性的影响,其中一个估计值的覆盖误差相对较小。