Context:
ITT analysis requires participants to be included even if they did not fully adhere to the
protocol. Participants who strayed from the protocol (for instance, by not adhering to the prescribed intervention, or by being withdrawn from active treatment) should still be kept in the analysis. An extreme variation of this is the participants who receive the treatment from the group they were not allocated to, who should be kept in their original group for the analysis. This issue causes no problems provided that, as a systematic reviewer, you can extract the appropriate data from the trial reports. The rationale for this approach is that, in the first instance, we want to estimate the effects of allocating an intervention in practice, not the effects in the subgroup of the participants who adhere to it.
In comparison, in a
http://en.wikipedia.org/wiki/Analysis_of_clinical_trials#Per_protocol,
[6] only patients who complete the entire clinical trial according to the protocol are counted towards the final results.
[7]