Dear Klazien,
Intention-to-treat analysis can best be thought of in terms of compliance.
There is no one correct way to analyze a trial; rather, one analyzes
different ways for different purposes. If one wants to know the average
result of applying the treatment to a population, then one uses
intention-to-treat analysis and includes all patients initially assigned to
the treatment or control group, regardless of whether they complied or
dropped out or crossed over. However, this obscures the effect of treatment
on those who comply, which is also a valuable thing to know. If I am a
patient, I want to know what to expect from the treatment if I respond to
treatment and comply. Averaging in a bunch of patients who don't respond or
don't comply confounds this result.
Statisticians tend to prefer intention-to-treat analysis, because it
maintains the purity of the original assignments. Clinicians and
manufacturers promoting an intervention tend to prefer to present results
only for those who respond and comply, to show the maximum effect. The
practical compromise is to present an intention-to-treat analysis as the
primary result, and to do a secondary analysis on those who respond and
comply. The proportion who respond and comply are themselves valuable
pieces of information that should be published.
The bottom line is that it is not necessary or desirable to do one or the
other; do both.
There was a set of articles discussing this in detail and proposing the "do
both" approach:
Efron B., 1998, Stat Med 17:259-50.
Urquhart J and De Klerk E, 1998, Stat Med 17:251-67.
Rubin D, 1998, Stat Med 17:371-85.
Cox D, 1998, Stat Med 17:387-89.
Also see:
Demissie K et al., 1998, J Clin Epidem 51(2):81-91.
David L. Doggett, Ph.D.
Senior Medical Research Analyst
Technology Assessment Group
ECRI, a non-profit health services research organization
5200 Butler Pike
Plymouth Meeting, PA 19462-1298, USA
Phone: +1 (610) 825-6000 ext.5509
Fax: +1(610) 834-1275
E-mail: [log in to unmask]
> -----Original Message-----
> From: Klazien Matter-Walstra [SMTP:[log in to unmask]]
> Sent: Sunday, August 20, 2000 7:05 AM
> To: EBH Discusision list
> Subject: WG: intention to treat
>
>
>
> Dear all,
>
> Can somebody explain what exactly is meant with " intention to treat"
> which
> can be found in the Cat Nipper
> Thanks and with best regards,
> Dr. Klazien Matter-Walstra
> _________________________________________
> Stiftung Paracelsus heute
> Ilgenweidstrasse 3
> CH-8840 Einsiedeln, Switzerland
> tel +41(0)55 4188195, fax +41(0)554188196
> mailto:[log in to unmask]
> http://www.paracelsus-heute.chnt
>
>
>
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|