An observational study found that authors of randomized controlled trials frequently use concealment of randomization and blinding, despite the failure to report these methods
Abstract
Background and objective Readers of randomized controlled trials (RCTs) commonly assume that what was not reported did not occur. We undertook an observational study to determine whether concealment of randomization or blinding was used in RCTs that failed to report these bias-reducing strategies.Methods We recorded the reporting of concealment of randomization and blinding in 105 RCTs. We subsequently contacted the authors and determined if they had used these methodological safeguards.Results We successfully obtained data from 98 authors. The authors in the full-text publications of these 98 RCTs failed to report the presence or absence of concealment of randomization in 55%, and the blinding status of participants in 26%, health care providers in 64%, data collectors in 84%, outcome assessors in 83%, and data analysts in 96%. In direct contact, authors frequently reported concealing randomization (96%; 95% confidence interval CI=87-100%), blinding participants (20%; 95% CI=7-41%), blinding health care providers (65%; 95% CI=52-77%), blinding data collectors (65%; 95% CI=53-75%), blinding outcome assessors (79%; 95% CI=69-87%), and blinding data analysts (50%; 95% CI=40-60%), despite not reporting the use of these methodological safeguards in their publications.Conclusions Readers should not assume that bias-reducing procedures not reported in an RCT did not occur.
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Blinding procedures are not always reported even when procedures have been adequately implemented.
“Blinding procedures are not always reported even when procedures have been adequately implemented [83, 84].”
From Blinding outcome assessors in randomised controlled trials of psychological interventions: how is it done? A narrative review (2026) · cites this paper as [83]
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“Blinding procedures are not always reported even when procedures have been adequately implemented [83, 84].”
- Authors
- Devereaux, P. J., Choi, P. T.-L., El-Dika, S., Bhandari, M., Montori, V. M., Schünemann, H. J., Garg, A. X., Busse, J. W., Heels-Ansdell, D., Ghali, W. A., Manns, B. J., & Guyatt, G. H.
- Affiliations
- McMaster University (CA)
- University of British Columbia (CA)
- University at Buffalo, State University of New York (US)
- Western University (CA)
- Corresponding author
- Devereaux, P.J.
- ORCID
- Venue
- Journal of Clinical Epidemiology
- Publisher
- Elsevier BV
- Published
- 2004-12
- Volume
- 57
- Issue
- 12
- Pages
- 1232-1236
- ISSN
- 0895-4356 (ISSN-L)
- OpenAlex
- W2089908284
- Cited by
- 209
- References
- 29
- Citations by year
- 2026: 4 · 2025: 1 · 2024: 5 · 2023: 4 · 2022: 11 · 2021: 6 · 2020: 1 · 2019: 8 · 2018: 4 · 2017: 7 · 2016: 14 · 2015: 11 · 2014: 12 · 2013: 11 · 2012: 16
- FWCI
- 12.70
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Journal of Clinical Epidemiology (publishedVersion)
- PubMed (publishedVersion)
- Topics
- Social Sciences › Decision Sciences › Statistics, Probability and Uncertainty › Meta-analysis and systematic reviews
- Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Clinical Trials
- Life Sciences › Pharmacology, Toxicology and Pharmaceutics › Pharmacology › Pharmaceutical industry and healthcare
- Keywords
- blinding, randomized controlled trials, reporting bias
- MeSH terms
- Double-Blind Method, Epidemiologic Methods, Humans, Research Personnel, Writing, Bias, Randomized Controlled Trials as Topic, Single-Blind Method
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