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

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

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Hollis, S., Campbell, F.·1999·BMJ

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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  1. Skog O-J. Interpreting trends in alcohol consumption and alcohol related damage. Alcohol Alcohol 1988;22:193-202.
  2. Robinson WS. Ecological correlations and the behavior of individual. American Sociological Review 1950;15:351-7.
  3. Skog O-J. Liver cirrhosis epidemiology: some methodological problems. Br J Addiction 1980;75:227-43.
  4. Hilton ME. Trends in U.S. drinking patterns: further evidence from the past twenty years. In: Clark WB, Hilton ME, eds. Alcohol in America: drink- ing practices and problems. Albany: State University of New York Press, 1991:121-38.
  5. Schmidt DN. Apparent risk factors for chronic and acute pancreatitis in Stockholm county: spirits but not wine and beer. Int J Pancreatol 1991;8:45-50.
  6. Kling W. Measurement of ethanol consumed in distilled spirits: revision. J Stud Alcohol 1991;52:503-4.
  7. Derr RF. Wine, alcohol, nutrition, and the risk of human mortality: corre- lation with rat and baboon studies. Biochem Arch 1996;12:277-82.
  8. Cochrane Controlled Trials Register. Cochrane library. Cochrane Collabo- ration. Oxford: Update Software, 1997.
  9. Cuzick J, Edwards R, Segnan N. Adjusting for non-compliance and con- tamination in randomized clinical trials. Stat Med 1997;16:1017-29.
  10. Goetghebeur EJ, Shapiro SH. Analysing non-compliance in clinical trials: ethical imperative or mission impossible? Stat Med 1996;15:2813-26.

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Authors
Hollis, S., & Campbell, F.
Affiliations
  • Lancaster University (GB)
  • AstraZeneca (United Kingdom) (GB)
Corresponding author
Hollis, S.
Venue
BMJ
Publisher
BMJ
Published
1999-09-11
Volume
319
Issue
7211
Pages
670-674
ISSN
  • 0007-1447 (ISSN-L)
  • 0959-8138
  • 1468-5833
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
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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