Combining treatment effects from mixed populations in meta-analysis: a review of methods

Abstract Background Meta-analysis is a useful method for combining evidence from multiple studies to detect treatment effects that could perhaps not be identified in a single study. While traditionally meta-analysis has assumed that populations of included studies are comparable, over recent years t...

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Main Authors: Lorna Wheaton, Sandro Gsteiger, Stephanie Hubbard, Sylwia Bujkiewicz
Format: Article
Language:English
Published: BMC 2025-04-01
Series:BMC Medical Research Methodology
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Online Access:https://doi.org/10.1186/s12874-025-02507-3
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author Lorna Wheaton
Sandro Gsteiger
Stephanie Hubbard
Sylwia Bujkiewicz
author_facet Lorna Wheaton
Sandro Gsteiger
Stephanie Hubbard
Sylwia Bujkiewicz
author_sort Lorna Wheaton
collection DOAJ
description Abstract Background Meta-analysis is a useful method for combining evidence from multiple studies to detect treatment effects that could perhaps not be identified in a single study. While traditionally meta-analysis has assumed that populations of included studies are comparable, over recent years the development of precision medicine has led to identification of predictive genetic biomarkers which has resulted in trials conducted in mixed biomarker populations. For example, early trials may be conducted in patients with any biomarker status with no subgroup analysis, later trials may be conducted in patients with any biomarker status and subgroup analysis, and most recent trials may be conducted in biomarker-positive patients only. This poses a problem for traditional meta-analysis methods which rely on the assumption of somewhat comparable populations across studies. In this review, we provide a background to meta-analysis methods allowing for synthesis of data with mixed biomarker populations across trials. Methods For the methodological review, PubMed was searched to identify methodological papers on evidence synthesis for mixed populations. Several identified methods were applied to an illustrative example in metastatic colorectal cancer. Results We identified eight methods for evidence synthesis of mixed populations where three methods are applicable to pairwise meta-analysis using aggregate data (AD), three methods are applicable to network meta-analysis using AD, and two methods are applicable to network meta-analysis using AD and individual participant data (IPD). The identified methods are described, including a discussion of the benefits and limitations of each method. Conclusions Methods for synthesis of data from mixed populations are split into methods which use (a) AD, (b) IPD, and (c) both AD and IPD. While methods which utilise IPD achieve superior statistical qualities, this is at the expense of ease of access to the data. Furthermore, it is important to consider the context of the decision problem in order to select the most appropriate modelling framework.
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spelling doaj-art-b4ef4c2e48334e4b94f2204a3e8a52ec2025-08-20T02:25:40ZengBMCBMC Medical Research Methodology1471-22882025-04-0125112110.1186/s12874-025-02507-3Combining treatment effects from mixed populations in meta-analysis: a review of methodsLorna Wheaton0Sandro Gsteiger1Stephanie Hubbard2Sylwia Bujkiewicz3Biostatistics Research Group, Department of Population Health Sciences, University of LeicesterGlobal Access, F Hoffman-La Roche AGBiostatistics Research Group, Department of Population Health Sciences, University of LeicesterBiostatistics Research Group, Department of Population Health Sciences, University of LeicesterAbstract Background Meta-analysis is a useful method for combining evidence from multiple studies to detect treatment effects that could perhaps not be identified in a single study. While traditionally meta-analysis has assumed that populations of included studies are comparable, over recent years the development of precision medicine has led to identification of predictive genetic biomarkers which has resulted in trials conducted in mixed biomarker populations. For example, early trials may be conducted in patients with any biomarker status with no subgroup analysis, later trials may be conducted in patients with any biomarker status and subgroup analysis, and most recent trials may be conducted in biomarker-positive patients only. This poses a problem for traditional meta-analysis methods which rely on the assumption of somewhat comparable populations across studies. In this review, we provide a background to meta-analysis methods allowing for synthesis of data with mixed biomarker populations across trials. Methods For the methodological review, PubMed was searched to identify methodological papers on evidence synthesis for mixed populations. Several identified methods were applied to an illustrative example in metastatic colorectal cancer. Results We identified eight methods for evidence synthesis of mixed populations where three methods are applicable to pairwise meta-analysis using aggregate data (AD), three methods are applicable to network meta-analysis using AD, and two methods are applicable to network meta-analysis using AD and individual participant data (IPD). The identified methods are described, including a discussion of the benefits and limitations of each method. Conclusions Methods for synthesis of data from mixed populations are split into methods which use (a) AD, (b) IPD, and (c) both AD and IPD. While methods which utilise IPD achieve superior statistical qualities, this is at the expense of ease of access to the data. Furthermore, it is important to consider the context of the decision problem in order to select the most appropriate modelling framework.https://doi.org/10.1186/s12874-025-02507-3Meta-analysisBiomarkerSubgroup
spellingShingle Lorna Wheaton
Sandro Gsteiger
Stephanie Hubbard
Sylwia Bujkiewicz
Combining treatment effects from mixed populations in meta-analysis: a review of methods
BMC Medical Research Methodology
Meta-analysis
Biomarker
Subgroup
title Combining treatment effects from mixed populations in meta-analysis: a review of methods
title_full Combining treatment effects from mixed populations in meta-analysis: a review of methods
title_fullStr Combining treatment effects from mixed populations in meta-analysis: a review of methods
title_full_unstemmed Combining treatment effects from mixed populations in meta-analysis: a review of methods
title_short Combining treatment effects from mixed populations in meta-analysis: a review of methods
title_sort combining treatment effects from mixed populations in meta analysis a review of methods
topic Meta-analysis
Biomarker
Subgroup
url https://doi.org/10.1186/s12874-025-02507-3
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