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Cited by 872Statistical Methods in Clinical TrialsMeta-analysis and systematic reviewsAdvanced Causal Inference Techniques

Bias in treatment assignment in controlled clinical trials

Chalmers, Thomas C., Celano, Paul, Sacks, Henry S., Smith, Harry·1983·New England Journal of Medicine
DOI 10.1056/nejm198312013092204
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Abstract

Controlled clinical trials of the treatment of acute myocardial infarction offer a unique opportunity for the study of the potential influence on outcome of bias in treatment assignment. A group of 145 papers was divided into those in which the randomization process was blinded (57 papers), those in which it may have been unblinded (45 papers), and those in which the controls were selected by a nonrandom process (43 papers). At least one prognostic variable was maldistributed (P less than 0.05) in 14.0 per cent of the blinded-randomization studies, in 26.7 per cent of the unblinded-randomization studies, and in 58.1 per cent of the nonrandomized studies. Differences in case-fatality rates between treatment and control groups (P less than 0.05) were found in 8.8 per cent of the blinded-randomization studies, 24.4 per cent of the unblinded-randomization studies, and 58.1 per cent of the nonrandomized studies. These data emphasize the importance of keeping those who recruit patients for clinical trials from suspecting which treatment will be assigned to the patient under consideration.

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Crossref · 10.1056/nejm198312013092204

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  • There is evidence that poor reporting of randomisation increases the odds of presenting 'significant' outcomes.

    “However, there is evidence that poor reporting of randomisation increases the odds of presenting 'significant' outcomes (Chalmers 1983;Schulz 1995).”

    From Psychological therapies for people with borderline personality disorder. (2012) · cites this paper as Chalmers 1983

  • Using a validated method of randomisation helps minimise selection bias and reduce systematic differences in the characteristics of animals allocated to different groups.

    “Using a validated method of randomisation helps minimise selection bias and reduce systematic differences in the characteristics of animals allocated to different groups [62–64].”

    From Reporting animal research: Explanation and elaboration for the ARRIVE guidelines 2.0 (2020) · cites this paper as [64]

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Authors
Chalmers, T. C., Celano, P., Sacks, H. S., & Smith, H.
Affiliations
Mount Sinai Hospital (US)
ORCID
Venue
New England Journal of Medicine
Publisher
Massachusetts Medical Society
Published
1983-12
Volume
309
Issue
22
Pages
1358-1361
ISSN
  • 0028-4793 (ISSN-L)
  • 1533-4406
DOI
10.1056/nejm198312013092204
OpenAlex
W2030192997
Cited by
864
References
13
Citations by year
2026: 1 · 2025: 3 · 2024: 8 · 2023: 6 · 2022: 10 · 2021: 9 · 2020: 8 · 2019: 14 · 2018: 7 · 2017: 18 · 2016: 15 · 2015: 19 · 2014: 15 · 2013: 18 · 2012: 19
FWCI
13.03
Type
journal article
Language
en
Open access
closed
Locations
  • New England Journal of Medicine (publishedVersion)
  • PubMed (publishedVersion)
  • DigitalGeorgetown (Georgetown University Library) (submittedVersion)
Topics
  • Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Clinical Trials
  • Social Sciences › Decision Sciences › Statistics, Probability and Uncertainty › Meta-analysis and systematic reviews
  • Physical Sciences › Mathematics › Statistics and Probability › Advanced Causal Inference Techniques
Keywords
unblinding, acute myocardial infarction, case fatality, control selection, clinical trial design
MeSH terms
Clinical Trials as Topic, Ethics, Medical, Humans, Myocardial Infarction, Outcome and Process Assessment, Health Care, Prognosis, Random Allocation, Research Design, Risk

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