Intention to treat analysis: Difference between revisions
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==Overview== | ==Overview== | ||
In [[epidemiology]], an '''intention to treat (ITT) analysis''' is an analysis based on the initial treatment intent, not on the treatment eventually administered. It is based on the assumption that, as in real life, sometimes patients do not all receive optimal treatment, even though that was the initial intention. For the purposes of analysis, the reasons why the patient did not receive the treatment are ignored. | In [[epidemiology]], an '''intention to treat (ITT) analysis''' is an analysis based on the initial treatment intent, not on the treatment eventually administered. The ITT analysis includes all patients randomized to a therapy irrespective of protocol deviations, discontinuation of study drug, drug administration errors, cross-over to another strategy, or withdrawal from the study by the subject. For example, in a trial comparing medical therapy to [[angioplasty]] for [[coronary artery disease]], those patients who were initially randomized to medical therapy but who crossed-over to receive an angioplasty instead due to a failure of medical therapy are analyzed as part of the medical therapy cohort. This form of analysis differs significantly from a [[per protocol]] (PP) analysis in which only those subjects are included who actually received study drug as specified in the study protocol. | ||
==Philosophy of an ITT Analysis== | |||
In a way, an ITT analysis tests a strategy of administering the therapy, rather than the therapy itself. It is based on the assumption that, as in real life, sometimes patients do not all receive optimal treatment, even though that was the initial intention. For the purposes of analysis, the reasons why the patient did not receive the treatment are ignored. | |||
==Rationale== | ==Rationale== | ||
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Overview
In epidemiology, an intention to treat (ITT) analysis is an analysis based on the initial treatment intent, not on the treatment eventually administered. The ITT analysis includes all patients randomized to a therapy irrespective of protocol deviations, discontinuation of study drug, drug administration errors, cross-over to another strategy, or withdrawal from the study by the subject. For example, in a trial comparing medical therapy to angioplasty for coronary artery disease, those patients who were initially randomized to medical therapy but who crossed-over to receive an angioplasty instead due to a failure of medical therapy are analyzed as part of the medical therapy cohort. This form of analysis differs significantly from a per protocol (PP) analysis in which only those subjects are included who actually received study drug as specified in the study protocol.
Philosophy of an ITT Analysis
In a way, an ITT analysis tests a strategy of administering the therapy, rather than the therapy itself. It is based on the assumption that, as in real life, sometimes patients do not all receive optimal treatment, even though that was the initial intention. For the purposes of analysis, the reasons why the patient did not receive the treatment are ignored.
Rationale
Intention to treat analyses are done to avoid the effects of crossover and drop-out, which may break the randomization to the treatment groups in a study. Intention to treat analysis provides information about the potential effects of treatment policy rather than on the potential effects of specific treatment.
In contrast, efficacy subset analysis selects the subset of the patients who received the treatment of interest--regardless of initial randomization--and who have not dropped out for any reason. This approach can :
- introduce biases to the statistical analysis
- inflate the type I error; this effect is greater the larger the trial[1].
Full application of intention to treat can only be performed where there is complete outcome data for all randomised subjects.
Although intention to treat is widely cited in published trials, it is often incorrectly described and its application may be flawed.
References
- ↑ Lachin JM (2000). "Statistical Considerations in the Intent-to-Treat Principle". Statistics in Medicine. 21 (3): 167–189. PMID 10822117. Unknown parameter
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See also
External links
- Intention to Treat - Bandolier's definition
- Intention to Treat - Tufts.edu
- What is meant by intention to treat analysis? Survey of published randomised controlled trials - BMJ