Allocation concealment: a methodological review
Related Experiment Video
Updated: May 11, 2026

An Experimental Analysis of Children's Ability to Provide a False Report about a Crime
Published on: May 3, 2016
Laura Clark1, Ulrike Schmidt, Puvan Tharmanathan
1York Trials Unit, Department of Health Sciences, University of York, York, UK. laura.clark@york.ac.uk
Rationale, Aims And Objectives:
The accurate reporting of the trial methodology and results is essential for accurate judgement on the quality of the research. This review aims to assess the impact of the adequacy of allocation concealment on treatment effect estimates.
Methods:
A search was performed in MEDLINE (via the Ovid platform) to identify all randomized controlled trials (RCTs) indexed in January 2011 within its set of 'core clinical journals'. Meta-regression was undertaken on a subset of two arm trials to quantify the association between adequacy of allocation concealment and effect size.
Results:
Adequate allocation concealment methods were used in 27% (n = 23) of included trials. There was insufficient information given in 68% (n = 58) of trials to make a judgement on allocation concealment. Meta-regression showed that there was a trend, not statistically significant, towards a smaller effect size between adequacy of allocation concealment and effect sizes.
Conclusion:
This review highlighted that research needs to be reported to a higher standard and there are many trials reporting poor methods of allocation concealment within the small sample of trials included in this review.
Related Concept Videos
Strategies for Assessing and Addressing Confounding
Confounding can be addressed at both the design phase of a study and through analytical methods after data...
Blinding
Understanding Deception
Confounding in Epidemiological Studies
Impression Management Techniques IV: Altercasting
Masking and Demasking Agents
There are many masking agents, such as cyanide, fluoride, triethanolamine, thiourea, and 2,3-bis(sulfanyl)propan-1-ol (formerly 2,3-dimercapto-1-propanol), with the masking agent chosen based on the metal...