Estimating required information size by quantifying diversity in random-effects model meta-analyses

<p>Abstract</p> <p>Background</p> <p>There is increasing awareness that meta-analyses require a sufficiently large information size to detect or reject an anticipated intervention effect. The required information size in a meta-analysis may be calculated from an anticip...

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Main Authors: Gluud Christian, Brok Jesper, Thorlund Kristian, Wetterslev Jørn
Format: Article
Language:English
Published: BMC 2009-12-01
Series:BMC Medical Research Methodology
Online Access:http://www.biomedcentral.com/1471-2288/9/86
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spelling doaj-cad04b8890ce42d89025818040b267ce2020-11-25T00:21:08ZengBMCBMC Medical Research Methodology1471-22882009-12-01918610.1186/1471-2288-9-86Estimating required information size by quantifying diversity in random-effects model meta-analysesGluud ChristianBrok JesperThorlund KristianWetterslev Jørn<p>Abstract</p> <p>Background</p> <p>There is increasing awareness that meta-analyses require a sufficiently large information size to detect or reject an anticipated intervention effect. The required information size in a meta-analysis may be calculated from an anticipated <it>a priori </it>intervention effect or from an intervention effect suggested by trials with low-risk of bias.</p> <p>Methods</p> <p>Information size calculations need to consider the total model variance in a meta-analysis to control type I and type II errors. Here, we derive an adjusting factor for the required information size under any random-effects model meta-analysis.</p> <p>Results</p> <p>We devise a measure of diversity (<it>D</it><sup>2</sup>) in a meta-analysis, which is the relative variance reduction when the meta-analysis model is changed from a random-effects into a fixed-effect model. <it>D</it><sup>2 </sup>is the percentage that the between-trial variability constitutes of the sum of the between-trial variability and a sampling error estimate considering the required information size. <it>D</it><sup>2 </sup>is different from the intuitively obvious adjusting factor based on the common quantification of heterogeneity, the inconsistency (<it>I</it><sup>2</sup>), which may underestimate the required information size. Thus, <it>D</it><sup>2 </sup>and <it>I</it><sup>2 </sup>are compared and interpreted using several simulations and clinical examples. In addition we show mathematically that diversity is equal to or greater than inconsistency, that is <it>D</it><sup>2 </sup>≥ <it>I</it><sup>2</sup>, for all meta-analyses.</p> <p>Conclusion</p> <p>We conclude that <it>D</it><sup>2 </sup>seems a better alternative than <it>I</it><sup>2 </sup>to consider model variation in any random-effects meta-analysis despite the choice of the between trial variance estimator that constitutes the model. Furthermore, <it>D</it><sup>2 </sup>can readily adjust the required information size in any random-effects model meta-analysis.</p> http://www.biomedcentral.com/1471-2288/9/86
collection DOAJ
language English
format Article
sources DOAJ
author Gluud Christian
Brok Jesper
Thorlund Kristian
Wetterslev Jørn
spellingShingle Gluud Christian
Brok Jesper
Thorlund Kristian
Wetterslev Jørn
Estimating required information size by quantifying diversity in random-effects model meta-analyses
BMC Medical Research Methodology
author_facet Gluud Christian
Brok Jesper
Thorlund Kristian
Wetterslev Jørn
author_sort Gluud Christian
title Estimating required information size by quantifying diversity in random-effects model meta-analyses
title_short Estimating required information size by quantifying diversity in random-effects model meta-analyses
title_full Estimating required information size by quantifying diversity in random-effects model meta-analyses
title_fullStr Estimating required information size by quantifying diversity in random-effects model meta-analyses
title_full_unstemmed Estimating required information size by quantifying diversity in random-effects model meta-analyses
title_sort estimating required information size by quantifying diversity in random-effects model meta-analyses
publisher BMC
series BMC Medical Research Methodology
issn 1471-2288
publishDate 2009-12-01
description <p>Abstract</p> <p>Background</p> <p>There is increasing awareness that meta-analyses require a sufficiently large information size to detect or reject an anticipated intervention effect. The required information size in a meta-analysis may be calculated from an anticipated <it>a priori </it>intervention effect or from an intervention effect suggested by trials with low-risk of bias.</p> <p>Methods</p> <p>Information size calculations need to consider the total model variance in a meta-analysis to control type I and type II errors. Here, we derive an adjusting factor for the required information size under any random-effects model meta-analysis.</p> <p>Results</p> <p>We devise a measure of diversity (<it>D</it><sup>2</sup>) in a meta-analysis, which is the relative variance reduction when the meta-analysis model is changed from a random-effects into a fixed-effect model. <it>D</it><sup>2 </sup>is the percentage that the between-trial variability constitutes of the sum of the between-trial variability and a sampling error estimate considering the required information size. <it>D</it><sup>2 </sup>is different from the intuitively obvious adjusting factor based on the common quantification of heterogeneity, the inconsistency (<it>I</it><sup>2</sup>), which may underestimate the required information size. Thus, <it>D</it><sup>2 </sup>and <it>I</it><sup>2 </sup>are compared and interpreted using several simulations and clinical examples. In addition we show mathematically that diversity is equal to or greater than inconsistency, that is <it>D</it><sup>2 </sup>≥ <it>I</it><sup>2</sup>, for all meta-analyses.</p> <p>Conclusion</p> <p>We conclude that <it>D</it><sup>2 </sup>seems a better alternative than <it>I</it><sup>2 </sup>to consider model variation in any random-effects meta-analysis despite the choice of the between trial variance estimator that constitutes the model. Furthermore, <it>D</it><sup>2 </sup>can readily adjust the required information size in any random-effects model meta-analysis.</p>
url http://www.biomedcentral.com/1471-2288/9/86
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