Intention to treat analysis
Encyclopedia
In epidemiology
, an intention to treat (ITT) analysis (sometimes also called intent to treat) is an analysis based on the initial treatment intent, not on the treatment eventually administered. ITT analysis is intended to avoid various misleading artifacts that can arise in intervention research. For example, if people who have a more refractory or serious problem tend to drop out at a higher rate, even a completely ineffective treatment may appear to be providing benefits if one merely compares the condition before and after the treatment for only those who finish the treatment (ignoring those who were enrolled originally, but have since been excluded or dropped out). For the purposes of ITT analysis, everyone who begins the treatment is considered to be part of the trial, whether he or she finishes it or not. This is different from per-protocol analysis
.
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:
Full application of intention to treat can only be performed where there is complete outcome data for all randomized subjects.
Although intention to treat is widely cited in published trials, it is often incorrectly described and its application may be flawed.
Epidemiology
Epidemiology is the study of health-event, health-characteristic, or health-determinant patterns in a population. It is the cornerstone method of public health research, and helps inform policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventive...
, an intention to treat (ITT) analysis (sometimes also called intent to treat) is an analysis based on the initial treatment intent, not on the treatment eventually administered. ITT analysis is intended to avoid various misleading artifacts that can arise in intervention research. For example, if people who have a more refractory or serious problem tend to drop out at a higher rate, even a completely ineffective treatment may appear to be providing benefits if one merely compares the condition before and after the treatment for only those who finish the treatment (ignoring those who were enrolled originally, but have since been excluded or dropped out). For the purposes of ITT analysis, everyone who begins the treatment is considered to be part of the trial, whether he or she finishes it or not. This is different from per-protocol analysis
Per-protocol analysis
In epidemiology, per-protocol analysis is a strategy of analysis in which only patients who complete the entire clinical trial are counted towards the final results. Intention to treat analysis uses data from all patients, including those who did not complete the study.- External links :* - of...
.
Rationale
Intention to treat analyses are done to avoid the effects of crossoverCrossover study
A crossover study is a longitudinal study in which subjects receive a sequence of different treatments . While crossover studies can be observational studies, many important crossover studies are controlled experiments, which are discussed in this article...
and drop-out
Dropping out
Dropping out means leaving a group for either practical reasons, necessities or disillusionment with the system from which the individual in question leaves....
, which may break the randomization
Randomization
Randomization is the process of making something random; this means:* Generating a random permutation of a sequence .* Selecting a random sample of a population ....
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 chance of a false positiveType I and type II errorsIn statistical test theory the notion of statistical error is an integral part of hypothesis testing. The test requires an unambiguous statement of a null hypothesis, which usually corresponds to a default "state of nature", for example "this person is healthy", "this accused is not guilty" or...
; this effect is greater the larger the trial.
Full application of intention to treat can only be performed where there is complete outcome data for all randomized subjects.
Although intention to treat is widely cited in published trials, it is often incorrectly described and its application may be flawed.
External links
- Intention to Treat Bandolier's definition
- Intention to Treat – Tufts.edu
- Intention-to-Treat Analysis – Bu.edu
- What is meant by intention to treat analysis? Survey of published randomised controlled trials – BMJBMJBMJ is a partially open-access peer-reviewed medical journal. Originally called the British Medical Journal, the title was officially shortened to BMJ in 1988. The journal is published by the BMJ Group, a wholly owned subsidiary of the British Medical Association...
- Intention-to-treat principle – CMAJ
- Inclusion of patients in clinical trial analysis: the intention-to-treat principle – eMJA