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Small studies may overestimate the effect sizes in critical care meta-analyses: a meta-epidemiological study

Overview of attention for article published in Critical Care, January 2013
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About this Attention Score

  • In the top 25% of all research outputs scored by Altmetric
  • High Attention Score compared to outputs of the same age (91st percentile)
  • High Attention Score compared to outputs of the same age and source (84th percentile)

Mentioned by

news
1 news outlet
twitter
10 tweeters
facebook
1 Facebook page

Readers on

mendeley
51 Mendeley
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Title
Small studies may overestimate the effect sizes in critical care meta-analyses: a meta-epidemiological study
Published in
Critical Care, January 2013
DOI 10.1186/cc11919
Pubmed ID
Authors

Zhongheng Zhang, Xiao Xu, Hongying Ni

Abstract

ABSTRACT: INTRODUCTION: Small-study effects refer to the fact that trials with limited sample sizes are more likely to report larger beneficial effects than large trials. However, this has never been investigated in critical care medicine. Thus, the present study aimed to examine the presence and extent of small-study effects in critical care medicine. METHODS: Critical care meta-analyses involving randomized controlled trials and reported mortality as an outcome measure were considered eligible for the study. Component trials were classified as large (≥100 patients per arm) and small (<100 patients per arm) according to their sample sizes. Ratio of odds ratio (ROR) was calculated for each meta-analysis and then RORs were combined using a meta-analytic approach. ROR<1 indicated larger beneficial effect in small trials. Small and large trials were compared in methodological qualities including sequence generating, blinding, allocation concealment, intention to treat and sample size calculation. RESULTS: A total of 27 critical care meta-analyses involving 317 trials were included. Of them, five meta-analyses showed statistically significant RORs <1, and other meta-analyses did not reach a statistical significance. Overall, the pooled ROR was 0.60 (95% CI: 0.53 to 0.68); the heterogeneity was moderate with an I2 of 50.3% (chi-squared = 52.30; P = 0.002). Large trials showed significantly better reporting quality than small trials in terms of sequence generating, allocation concealment, blinding, intention to treat, sample size calculation and incomplete follow-up data. CONCLUSIONS: Small trials are more likely to report larger beneficial effects than large trials in critical care medicine, which could be partly explained by the lower methodological quality in small trials. Caution should be practiced in the interpretation of meta-analyses involving small trials.

Twitter Demographics

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Mendeley readers

The data shown below were compiled from readership statistics for 51 Mendeley readers of this research output. Click here to see the associated Mendeley record.

Geographical breakdown

Country Count As %
Canada 2 4%
United States 1 2%
France 1 2%
United Kingdom 1 2%
Unknown 46 90%

Demographic breakdown

Readers by professional status Count As %
Researcher 11 22%
Student > Ph. D. Student 7 14%
Student > Bachelor 6 12%
Student > Master 6 12%
Professor > Associate Professor 4 8%
Other 12 24%
Unknown 5 10%
Readers by discipline Count As %
Medicine and Dentistry 26 51%
Psychology 4 8%
Agricultural and Biological Sciences 2 4%
Nursing and Health Professions 2 4%
Biochemistry, Genetics and Molecular Biology 1 2%
Other 6 12%
Unknown 10 20%

Attention Score in Context

This research output has an Altmetric Attention Score of 15. This is our high-level measure of the quality and quantity of online attention that it has received. This Attention Score, as well as the ranking and number of research outputs shown below, was calculated when the research output was last mentioned on 01 July 2020.
All research outputs
#1,342,092
of 15,561,035 outputs
Outputs from Critical Care
#1,311
of 4,922 outputs
Outputs of similar age
#21,289
of 261,683 outputs
Outputs of similar age from Critical Care
#28
of 184 outputs
Altmetric has tracked 15,561,035 research outputs across all sources so far. Compared to these this one has done particularly well and is in the 91st percentile: it's in the top 10% of all research outputs ever tracked by Altmetric.
So far Altmetric has tracked 4,922 research outputs from this source. They typically receive a lot more attention than average, with a mean Attention Score of 15.5. This one has gotten more attention than average, scoring higher than 73% of its peers.
Older research outputs will score higher simply because they've had more time to accumulate mentions. To account for age we can compare this Altmetric Attention Score to the 261,683 tracked outputs that were published within six weeks on either side of this one in any source. This one has done particularly well, scoring higher than 91% of its contemporaries.
We're also able to compare this research output to 184 others from the same source and published within six weeks on either side of this one. This one has done well, scoring higher than 84% of its contemporaries.