Cited by 2,160Statistical Methods in Clinical TrialsMeta-analysis and systematic reviewsAdvanced Causal Inference Techniques

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What is meant by intention to treat analysis? Survey of published randomised controlled trials

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Hollis, S., Campbell, F.·1999·BMJ

DOI 10.1136/bmj.319.7211.670PMC PMC28218

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Abstract

Abstract Objectives: To assess the methodological quality of intention to treat analysis as reported in randomised controlled trials in four large medical journals. Design: Survey of all reports of randomised controlled trials published in 1997 in the BMJ, Lancet, JAMA, and New England Journal of Medicine. Main outcome measures: Methods of dealing with deviations from random allocation and missing data. Results: 119 (48%) of the reports mentioned intention to treat analysis. Of these, 12 excluded any patients who did not start the allocated intervention and three did not analyse all randomised subjects as allocated. Five reports explicitly stated that there were no deviations from random allocation. The remaining 99 reports seemed to analyse according to random allocation, but only 34 of these explicitly stated this. 89 (75%) trials had some missing data on the primary outcome variable. The methods used to deal with this were generally inadequate, potentially leading to a biased treatment effect. 29 (24%) trials had more than 10% of responses missing for the primary outcome, the methodsof handling the missing responses were similar in this subset. Conclusions: The intention to treat approach is often inadequately described and inadequately applied. Authors should explicitly describe the handling of deviations from randomised allocation and missing responses and discuss the potential effect of any missing response. Readers should critically assess the validity of reported intention to treat analyses. Key messages Intention to treat gives a pragmatic estimate of the benefit of a change in treatment policy rather than of potential benefit in patients who receive treatment exactly as planned Full application of intention to treat is possible only when complete outcome data are available for all randomised subjects About half of all published reports of randomised controlled trials stated that intention to treat was used, but handling of deviations from randomised allocation varied widely Many trials had some missing data on the primary outcome variable, and methods used to deal with this were generally inadequate, potentially leading to bias Intention to treat analyses are often inadequately described and inadequately applied

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Authors: Hollis, S., & Campbell, F.
Affiliations: Lancaster University (GB)
AstraZeneca (United Kingdom) (GB)
Corresponding author: Hollis, S.
ORCID: Campbell, F.
Venue: BMJ
Publisher: BMJ
Published: 1999-09-11
Volume: 319
Issue: 7211
Pages: 670-674
ISSN: 0007-1447 (ISSN-L)
0959-8138
1468-5833
DOI: 10.1136/bmj.319.7211.670
PMC: PMC28218
OpenAlex: W1984052453
Cited by: 2,160
References: 67
Citations by year: 2026: 32 · 2025: 42 · 2024: 40 · 2023: 67 · 2022: 68 · 2021: 66 · 2020: 78 · 2019: 82 · 2018: 74 · 2017: 73 · 2016: 106 · 2015: 107 · 2014: 144 · 2013: 128 · 2012: 128
FWCI: 7.30
Type: journal article
Language: en
Open access: bronze
doi.org
Locations: BMJ (publishedVersion)
Europe PMC (PubMed Central) (publishedVersion)
PubMed Central (publishedVersion)
PubMed (publishedVersion)
Research Explorer (The University of Manchester) (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: intention-to-treat analysis, randomized controlled trials, methodological quality, missing data, bias in treatment effect estimation, reporting practices, medical journals
MeSH terms: Data Collection, Decision Making, Randomized Controlled Trials as Topic, Treatment Refusal, Treatment Outcome, Patient Selection

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