Meta-analysis in medical research: Potentials and limitations
Abstract
Meta-analysis, the statistical combination of results from several studies to produce a single estimate of a treatment effect or size of an association, continues to attract controversy. We illustrate and discuss the promises and limitations of meta-analysis. Meta-analysis of clinical trials can prevent delays in the introduction of effective treatments or lead to the timely identification of adverse effects. However, meta-analyses are liable to numerous biases, both at the level of the individual study and the selection of studies for inclusion in meta-analysis. The biases and confounding factors that threaten the validity of individual studies will also affect meta-analyses of observational studies. We argue that meta-analyses should only be performed within the framework of systematic reviews that have been prepared using methods that minimize bias and address the combinability of studies.
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Synthesis of evidence from observational studies differs from the approach used when examining evidence from RCTs.
“Importantly, synthesis of evidence from observational studies differs from the approach used when examining evidence from RCTs.”
From Methods to systematically review and meta-analyse observational studies: a systematic scoping review of recommendations (2018) · cites this paper as [8]
The process of defining the research question and conducting an adequate literature search is likely to be more iterative in reviews of observational studies than in reviews of RCTs.
“the process of defining the research question and conducting an adequate literature search is likely to be more iterative than in reviews of RCTs”
From Methods to systematically review and meta-analyse observational studies: a systematic scoping review of recommendations (2018) · cites this paper as [8]
Risk of bias assessment is different in reviews of observational studies compared with reviews of RCTs.
“the risk of bias assessment is different”
From Methods to systematically review and meta-analyse observational studies: a systematic scoping review of recommendations (2018) · cites this paper as [8]
Decisions around combining results in meta-analysis of observational studies require more careful consideration to avoid precise but misleading results.
“decisions around combining results require more careful consideration to avoid precise but misleading results from meta-analysis [8, 9].”
From Methods to systematically review and meta-analyse observational studies: a systematic scoping review of recommendations (2018) · cites this paper as [8]
Twenty-five (27%) articles gave recommendations on item "considering different study designs", with publication dates between 1995 and 2016 (median year 2007).
“Twenty-five (27%) articles gave recommendations on item “considering different study designs” [8, 29, 34, 35, 37–39, 42, 44, 49, 51, 56, 61, 65, 70, 73, 75, 76, 77–83], with publication dates between 1995 and 2016 (median year of publication 2007).”
From Methods to systematically review and meta-analyse observational studies: a systematic scoping review of recommendations (2018) · cites this paper as [8]
Some authors agreed that study design should be investigated as a potential source of between study heterogeneity, and others recommended presenting meta-analyses for each study type alongside results from an overall meta-analysis.
“Some authors agreed that study design should be investigated as a potential source of between study heterogeneity [8, 34, 42, 77], and others recommended presenting meta-analyses for each study type alongside results from an overall meta-analysis [42, 83].”
From Methods to systematically review and meta-analyse observational studies: a systematic scoping review of recommendations (2018) · cites this paper as [8]
Fifty-two articles (56%) provided recommendations on the statistical analysis in the context of meta-analysis of observational studies, with publication dates between 1994 and 2016 (median year 2006).
“Fifty-two articles (56%), provided recommendations on the statistical analysis in the context of meta-analysis of observational studies [8, 12, 16, 29–31, 33–36, 38, 41–44, 47, 48, 52, 54–56, 61, 66, 70, 72, 73, 77, 79–83, 85, 87, 96, 100, 101, 103–105, 107–118], with publication dates between 1994 and 2016 (median year of publication 2006).”
From Methods to systematically review and meta-analyse observational studies: a systematic scoping review of recommendations (2018) · cites this paper as [8]
Thirty-nine articles (42%) provided recommendations on heterogeneity and its assessment, with publication dates between 1994 and 2016 (median year 2006).
“Thirty-nine articles (42%) provided recommendations on heterogeneity and its assessment, [8, 12, 16, 29, 30, 33, 34, 36, 38, 39, 41–44, 47, 49–52, 54–56, 61, 66, 70, 72, 77, 82, 85, 87, 98, 100–107] with publication dates between 1994 and 2016 (median year of publication 2006).”
From Methods to systematically review and meta-analyse observational studies: a systematic scoping review of recommendations (2018) · cites this paper as [8]
The use of a random-effects model for meta-analysis of observational studies by default was frequently recommended.
“Second, the use of a random-effects model for meta-analysis of observational studies by default was frequently recommended [8, 16, 29, 34, 70, 77, 100, 101].”
From Methods to systematically review and meta-analyse observational studies: a systematic scoping review of recommendations (2018) · cites this paper as [8]
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- Authors
- Zwahlen, M., Renehan, A., & Egger, M.
- Affiliations
- University of Bern (CH)
- The Christie Hospital (GB)
- Corresponding author
- Zwahlen, Marcel
- Venue
- Urologic Oncology: Seminars and Original Investigations
- Publisher
- Elsevier BV
- Published
- 2008-05
- Volume
- 26
- Issue
- 3
- Pages
- 320-329
- ISSN
- 1078-1439 (ISSN-L)
- OpenAlex
- W2171657748
- Cited by
- 70
- References
- 121
- Citations by year
- 2026: 2 · 2025: 2 · 2024: 7 · 2023: 4 · 2022: 2 · 2021: 2 · 2020: 5 · 2018: 2 · 2017: 6 · 2016: 5 · 2015: 5 · 2014: 4 · 2013: 5 · 2012: 3
- FWCI
- 3.69
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Urologic Oncology Seminars and Original Investigations (publishedVersion)
- PubMed (publishedVersion)
- BORIS (University Library Bern) (submittedVersion)
- Topics
- Social Sciences › Decision Sciences › Statistics, Probability and Uncertainty › Meta-analysis and systematic reviews
- Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Epidemiology
- Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Clinical Trials
- Keywords
- meta-analysis, systematic reviews, bias in clinical trials, confounding, observational studies, treatment effect estimation, adverse effects
- MeSH terms
- Humans, Medical Oncology, Myocardial Infarction, Review Literature as Topic, Urology, Meta-Analysis as Topic, Controlled Clinical Trials as Topic, Biomedical Research
About these checks
Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.
Statistics and arithmetic are recomputed, not judged.
Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.
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