Randomised controlled trials are used to assess the benefits and harms of interventions in health care. If conducted properly, they minimise the risk of bias (threats to internal validity), particularly selection bias.1 2
There is, however, considerable evidence that trials are not always well reported,3 4
and this can be associated with bias, such as selective reporting of outcomes.5
The usefulness of a trial report also depends on the clarity with which it details the relevance of its interventions, participants, outcomes, and design to the clinical, health service, or policy question it examines. Furthermore, a trial may be valid and useful in the healthcare setting in which it was conducted but have limited applicability (also known as generalisability or external validity) beyond this because of differences between the trial setting and other settings to which its results are to be extrapolated.
Schwartz and Lellouch6
coined the terms “pragmatic” to describe trials designed to help choose between options for care, and “explanatory” to describe trials designed to test causal research hypotheses—for example, that an intervention causes a particular biological change. Table 1 shows some key differences between explanatory and pragmatic trials. Table 2 compares a trial that was highly explanatory in attitude7
with one that was highly pragmatic.8
There is a continuum rather than a dichotomy between explanatory and pragmatic trials. In fact, Schwartz and Lellouch characterised pragmatism as an attitude to trial design rather than a characteristic of the trial itself. The pragmatic attitude favours design choices that maximise applicability of the trial’s results to usual care settings, rely on unarguably important outcomes such as mortality and severe morbidity, and are tested in a wide range of participants.9 10 11
As Schwartz and Lellouch wrote: “Most trials done hitherto have adopted the explanatory approach without question; the pragmatic approach would often have been more justifiable.”6
Key differences between trials with explanatory and pragmatic attitudes, adapted from a table presented at the 2008 Society for Clinical Trials meeting by Marion Campbell, University of Aberdeen
Comparison of trial that was highly explanatory in attitude with trial that was highly pragmatic
Calls have been made for more pragmatic trials in general,6 12 13
and in relation to specific clinical problems.14 15 16
Articles have been published discussing the characteristics and value of pragmatic trials17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35
or proposing improvements in the design and conduct of these trials.36 37 38
Patients, advocacy groups, clinicians, systematic reviewers, funders, and policymakers want to use the results of randomised controlled trials. As such, a clear description of the design and execution of the trial, the intervention and comparator, and the setting in which health care is provided may simplify their decision on the likely benefits, harms, and costs to be expected when implementing the intervention in their own situation. There is, however, no accepted standard to guide reporting on the aspects of design and conduct of trials that affect their usefulness for decision making, particularly considerations that would affect the applicability of the results.
We propose here guidance for reporting pragmatic trials, as a specific extension of the CONSORT statement. Our aim is to identify information which, if included in reports of pragmatic trials, will help users determine whether the results are applicable to their own situation and whether the intervention might be feasible and acceptable. Reporting this information is crucial for any trial that is intended to inform decisions about practice.