SynthesisBMJ open2017
Unequal cluster sizes in stepped-wedge cluster randomised trials: a systematic review.
Synthesis in BMJ open, 2017. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 14 papers, 2 of them syntheses that pooled it.
What it found
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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.
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.
Who cites it
14 citing papers in PubMed, 2 syntheses or guidelines pooled it.
- Reported problems and responses during the conduct of stepped-wedge cluster randomized trials in healthcare settings: a qualitative systematic review.International journal of epidemiology · 2026Pooled it
- The current use of feasibility studies in the assessment of feasibility for stepped-wedge cluster randomised trials: a systematic review.BMC medical research methodology · 2019Pooled it
- Statistical Analysis Plan for the INTEnsive Care Bundle with Blood Pressure Reduction in Acute Cerebral Hemorrhage Trial: A Stepped-Wedge Cluster Randomized Controlled Trial.Cerebrovascular diseases (Basel, Switzerland) · 2023Trial
- Trial
- Effect of a novel vital sign device on maternal mortality and morbidity in low-resource settings: a pragmatic, stepped-wedge, cluster-randomised controlled trial.The Lancet. Global health · 2019Trial
- Finite-Sample Adjustments in Estimating Equations for Correlated Overdispersed Count Outcomes With Application to Cluster Randomized Trials.Statistics in medicine · 2026Article
- Article
- Adherence to key recommendations for design and analysis of stepped-wedge cluster randomized trials: A review of trials published 2016-2022.Clinical trials (London, England) · 2024Review
- Influential methods reports for group-randomized trials and related designs.Clinical trials (London, England) · 2022Article
- Stepped Wedge Cluster Randomized Trials: A Methodological Overview.World neurosurgery · 2022Review
- Ratio estimators of intervention effects on event rates in cluster randomized trials.Statistics in medicine · 2022Article
- Comparison of small-sample standard-error corrections for generalised estimating equations in stepped wedge cluster randomised trials with a binary outcome: A simulation study.Statistical methods in medical research · 2021Article
- Methods for dealing with unequal cluster sizes in cluster randomized trials: A scoping review.PloS one · 2021Article
- Power calculation for cross-sectional stepped wedge cluster randomized trials with variable cluster sizes.Biometrics · 2020Article
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
3 authors.
Funding
No grant is acknowledged in the PubMed record.
Abstract
objectivesTo investigate the extent to which cluster sizes vary in stepped-wedge cluster randomised trials (SW-CRT) and whether any variability is accounted for during the sample size calculation and analysis of these trials.
settingAny, not limited to healthcare settings.
participantsAny taking part in an SW-CRT published up to March 2016. PRIMARY AND SECONDARY OUTCOME MEASURES: The primary outcome is the variability in cluster sizes, measured by the coefficient of variation (CV) in cluster size. Secondary outcomes include the difference between the cluster sizes assumed during the sample size calculation and those observed during the trial, any reported variability in cluster sizes and whether the methods of sample size calculation and methods of analysis accounted for any variability in cluster sizes.
resultsOf the 101 included SW-CRTs, 48% mentioned that the included clusters were known to vary in size, yet only 13% of these accounted for this during the calculation of the sample size. However, 69% of the trials did use a method of analysis appropriate for when clusters vary in size. Full trial reports were available for 53 trials. The CV was calculated for 23 of these: the median CV was 0.41 (IQR: 0.22-0.52). Actual cluster sizes could be compared with those assumed during the sample size calculation for 14 (26%) of the trial reports; the cluster sizes were between 29% and 480% of that which had been assumed.
conclusionsCluster sizes often vary in SW-CRTs. Reporting of SW-CRTs also remains suboptimal. The effect of unequal cluster sizes on the statistical power of SW-CRTs needs further exploration and methods appropriate to studies with unequal cluster sizes need to be employed.
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