Users' Guides to the Medical Literature
Guyatt G, Rennie D, Meade MO, Cook DJ
Part B Therapy
Chapter 9.4. The Principle of Intention to Treat
Gordon Guyatt, Victor Montori, P. J. Devereaux, Pierre Durieux
How Should Randomized Trials Deal With Treatment-Arm Patients Who Do Not Receive Treatment?
Topics Discussed:
adherence, intention to treat, intention to treat analysis, intervention/exposure, medication adherence, nonadherent, per-protocol analysis, randomized controlled trials
Excerpt:
"If patients do not take their medication, they are not going
to get any benefit. Furthermore, we do not need randomized trials—or
studies of any kind—to demonstrate this lack of benefit.
One might therefore reason that, in a randomized trial,
investigators should compare patients in the experimental group
who received treatment with patients in the control group who
did not. As it turns out, however, doing so is a mistake. We need
to know about all the patients in a trial, including those in the experimental
group who do not adhere to or complete therapy.Imagine a randomized trial studying patients
with cerebrovascular disease. The trial compares administration
of aspirin alone with that of aspirin along with an experimental
surgical procedure. Assume that, although the investigators conducting
the trial do not know it, the underlying true effect of the surgical
procedure is zero; patients in the surgical arm of the study do
neither better nor worse than those in the aspirin-only arm...."
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