BMJ 2002;325:652-654 ( 21 September )

Education and debate

Post-randomisation exclusions: the intention to treat principle and excluding patients from analysis

Dean Fergusson, scientist ^a, Shawn D Aaron, assistant professor ^a, Gordon Guyatt, professor ^b, Paul Hébert, associate professor ^a. 

^a Ottawa Health Research Institute, 501 Smyth Road, Box 201, Ottawa, ON, Canada K1H 8L6, ^b Departments of Clinical Epidemiology and Biostatistics and Medicine, McMaster University, Hamilton, ON, Canada L8N 3Z5

Correspondence to: D Fergusson dafergusson@ohri.ca

The first 150 words of the full text of this article appear below.

When is it legitimate to exclude randomised patients from the analysis of data in clinical trials? Basing their analysis on the desirability of minimising bias and random error, the authors consider the circumstances when it may be possible to exclude patients, even in an intention to treat trial

Most clinical researchers and statisticians agree that the primary analysis of data in a randomised clinical trial should compare patients according to the group to which they were randomly allocated, regardless of patients' compliance, crossover to other treatments, or withdrawal from the study. Such an analysis is referred to as an intention to treat or an "as randomised" analysis. Proponents argue that the intention to treat approach

• Helps preserve prognostic balance in the study arms
• Limits inferences based on arbitrary or ad hoc subgroups of patients in the trial
• Emphasises greater accountability for all patients entered into the study and consequently minimises . . . [Full text of this article]

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