Introduction
Randomised controlled trials are the best research design for
decisions about the effect of different interventions but
randomisation does not, of itself, promote the applicability
(sometimes called 'generalisability') of a trial's results to
situations other than the precise one in which the trial was
done. Unfortunately, it is very common that an intervention
that has been shown to be effective in a trial context never
becomes part of routine healthcare practice because, for one reason
or another, it is not easily applicable to the 'real world'. While
methodologists and trialists have rightly paid great attention to
internal validity, much less has generally been given to
applicability (1).
The Normalisation Process Theory (NPT) may be able to help
because it offers a theoretical framework with which to optimise
the development a trial intervention. There are three main ways in
which the theory could do this:
- to support intervention design
- to describe the context of a trial
- to support the interpretation of a trial's results
Before discussing these three points further it is important to
note that NPT could also be used to optimise the trial parameters
by asking eg. To what extent do proposed trial procedures 'fit'
with existing and routine ways of working? Do trial procedures
become routine during the course of the trial? Addressing these
questions might be a way of improving the applicability of the
intervention from the trial context to the 'real world' to which we
now return. How you might use NPT to do this wouldn't be different
to the three sections mentioned above, just the focus.
Finally, it is important to remember that NPT is neither a
protocol about how to do a trial nor a recipe for how to understand
it. It is designed to sensitise thinking about certain
aspects of trials. NPT can be used alongside other methods and
methodologies to support your trial. It is intended to be
used in a flexible manner depending on the specifics of a given
trial.
Things to consider
- Who are the people I expect to use the results of my trial and
what can I do to make sure that these people will not be forced to
dismiss my trial as irrelevant to them, their patients, or their
healthcare systems?
References and further reading
- Treweek S,
Zwarenstein M. Making trials matter: pragmatic and
explanatory trials and the problem of applicability. Trials
2009; 10:37. Back to
text
- Zwarenstein M, Treweek S. What kind of randomized trials
do patients and clinicians need? ACP Journal Club 2009; 150:
JC5-2-3.
