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

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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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The Importance of Beta, the Type II Error and Sample Size in the Design and Interpretation of the Randomized Control Trial: Survey of 71 Negative Trials
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1981, Milbank Mem Fund Q, 0, 324

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Authors: Chalmers, T. C., Celano, P., Sacks, H. S., & Smith, H.
Affiliations: Mount Sinai Hospital (US)
ORCID: Celano, Paul
Sacks, Henry S.
Smith, Harry
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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Bias in Treatment Assignment in Controlled Clinical Trials

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