Evidence map›Paper›PMID 23616031›Full record

SynthesisBMJ (Clinical research ed.)2013

Influence of trial sample size on treatment effect estimates: meta-epidemiological study.

Agnes Dechartres, Ludovic Trinquart, Isabelle Boutron, Philippe Ravaud

Abstract readMeta-AnalysisReview
PubMed Full text at PMC Publisher
In one paragraph

Synthesis in BMJ (Clinical research ed.), 2013. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 247 papers, 116 of them syntheses that pooled it.

0numbers the graph read from it
0cells of the map it votes in
247citing papers in PubMed, 116 pooled it
–field-weighted citation impact
1 · What the graph read from it

What it found

Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.

The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.

2 · The registry

The trial behind it

Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.

Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.

3 · Its place in the literature

Who cites it

247 citing papers in PubMed, 116 syntheses or guidelines pooled it.

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  14. Pain in adults with cerebral palsy: A systematic review.Developmental medicine and child neurology · 2025
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187 more citing papers are in PubMed but not listed here.

4 · The record

Corrections and comments

PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.

5 · Who and what money

Authors and funding

4 authors.

Agnes DechartresINSERM, U738, Paris, France. agnes.dechartres@htd.aphp.fr
Ludovic Trinquart
Isabelle Boutron
Philippe Ravaud

Funding

No grant is acknowledged in the PubMed record.

6 · The paper itself

Abstract

objectiveTo assess the influence of trial sample size on treatment effect estimates within meta-analyses.

designMeta-epidemiological study. DATA SOURCES: 93 meta-analyses (735 randomised controlled trials) assessing therapeutic interventions with binary outcomes, published in the 10 leading journals of each medical subject category of the Journal Citation Reports or in the Cochrane Database of Systematic Reviews. DATA EXTRACTION: Sample size, outcome data, and risk of bias extracted from each trial. DATA SYNTHESIS: Trials within each meta-analysis were sorted by their sample size: using quarters within each meta-analysis (from quarter 1 with 25% of the smallest trials, to quarter 4 with 25% of the largest trials), and using size groups across meta-analyses (ranging from <50 to ≥ 1000 patients). Treatment effects were compared within each meta-analysis between quarters or between size groups by average ratios of odds ratios (where a ratio of odds ratios less than 1 indicates larger effects in smaller trials).

resultsTreatment effect estimates were significantly larger in smaller trials, regardless of sample size. Compared with quarter 4 (which included the largest trials), treatment effects were, on average, 32% larger in trials in quarter 1 (which included the smallest trials; ratio of odds ratios 0.68, 95% confidence interval 0.57 to 0.82), 17% larger in trials in quarter 2 (0.83, 0.75 to 0.91), and 12% larger in trials in quarter 3 (0.88, 0.82 to 0.95). Similar results were obtained when comparing treatment effect estimates between different size groups. Compared with trials of 1000 patients or more, treatment effects were, on average, 48% larger in trials with fewer than 50 patients (0.52, 0.41 to 0.66) and 10% larger in trials with 500-999 patients (0.90, 0.82 to 1.00).

conclusionsTreatment effect estimates differed within meta-analyses solely based on trial sample size, with stronger effect estimates seen in small to moderately sized trials than in the largest trials.

Indexed as

Patient SelectionPeriodicals as TopicBiasHumansRandomized Controlled Trials as Topic

Identifiers

PMID23616031
PMCPMC3634626

What OpenQuestion holds

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Registered trials

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Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.