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Updated: Aug 15, 2026

The Adjuvant Efficacy of Angong Niuhuang Pill in the Treatment of Viral Encephalitis: A Meta-Analysis of Randomized Controlled Trials
Published on: April 19, 2024
Outcome selection bias in meta-analysis
P R Williamson1, C Gamble, D G Altman
1Centre for Medical Statistics and Health Evaluation, Shelley's Cottage, Brownlow Street, University of Liverpool, Liverpool L69 3GS, UK. prw@liv.ac.uk
Abstract:
Publication bias has been previously identified as a threat to the validity of a meta-analysis. Recently, new evidence has documented an additional threat to validity, the selective reporting of trial outcomes within published studies. Several diseases have several possible measures of outcome. Some articles might report only a selection of those outcomes, perhaps those with statistically significant results. In this article, we review this problem while addressing the questions: what is within-study selective reporting? how common is it? why is it done? how can it mislead? how can it be detected?, and finally, what is the solution? We recommend that both publication bias and selective reporting should be routinely investigated in systematic reviews.
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