Pragmatic trials are randomized and may use a placebo
Keenan Research Centre, Li Ka Shing Knowledge Institute of St. Michael's Hospital, Toronto, Ontario, Canada
Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada
Preventive and International Health Care Unit, Norwegian Knowledge Centre for the Health Services, Oslo, Norway
Division of Clinical & Population Sciences and Education, University of Dundee, Dundee, UK
Norwegian Knowledge Centre for the Health Services, Oslo, Norway
Division of Public Health Sciences, Wake Forest University School of Medicine, Winston-Salem, NC, USA
published online 22 February 2010.
Article Outline
In reply:
We would like to thank Prof. Windeler for his thoughtful letter and the editors of the journal for the invitation to respond to his comments.
1.As we previously said [1], the labels “pragmatic trial” and “explanatory trial” are indeed oversimplifications that imply a simple dichotomy when there is, in fact, a multidimensional continuum. However, the labels are not without value for the planning of a trial. We think that it is important for trialists to consider the “ideal” (or, more specifically, the extremes for each relevant dimension) to make the design decisions that best support their primary goal in doing a trial.
2.We agree that trials of all kinds are concerned with questions of causal relationships. It is the design decisions with regard to patients, setting, application of treatment, and outcome, among other things, that distinguish the explanatory and pragmatic approaches and thereby affect how the trial results are interpreted and used.
3.Prof. Windeler is correct that our (and Schwartz and Lellouch's [2]) use of “pragmatism” does not suggest nonrandomized designs. Random allocation is common to the full multidimensional continuum of explanatory and pragmatic trials.
Lastly, Prof. Windeler points out that placebos can be used in both pragmatic and explanatory trials. We agree that the use of a placebo is not a defining feature of explanatory trials. Consequently, we did not say much about this. We do not, however, agree that a finding from a “pragmatic trial” that a new treatment is as good as usual care is never of value to decision makers, when the effects of usual care are uncertain. If the new treatment costs less, and one was confident that it was not worse than usual care, one would likely use it. If it costs more, one would likely not use it unless there was some other advantage, such as less risk of adverse effects. If it costs the same and there were no other advantages, one would likely continue with usual care. Although important uncertainty about the effects of usual care should lead trialists to consider the use of a placebo when their goal is pragmatic, there may sometimes be good reasons for not doing so.
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References
- Thorpe KE, Zwarenstein M, Oxman AD, Treweek S, Furberg CD, Altman DG, et al. A pragmatic–explanatory continuum indicator summary (PRECIS): a tool to help trial designers. J Clin Epidemiol. 2009;62:464–475
- Schwartz D, Lellouch J. Explanatory and pragmatic attitudes in therapeutical trials. J Chron Dis. 1967;20:637–648
PII: S0895-4356(09)00352-7
doi:10.1016/j.jclinepi.2009.09.014
© 2010 Elsevier Inc. All rights reserved.
