Intentiontotreat analysis

A major source of bias in a randomized trial can be the exclusion of patients from the analysis. Patients maybe excluded for a variety of reasons including:

♦ further tests carried out after randomization show the patient is ineligible,

♦ the patient does not receive any of their allocated treatment,

♦ the patient receives some, but not all their allocated treatment,

♦ the patient is not assessed for the outcome of interest, such as response,

♦ an independent review reports the patient as ineligible.

Although all these may appear to be legitimate and sensible reasons to exclude patients from analysis, it actually transpires that most are likely to introduce bias into the analysis. The reasons for this are discussed below.

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