explanatory trial

explanatory trial

A generic term of art referring to a clinical trial that tests whether an intervention can have a beneficial effect in an ideal situation. Such trials seek to maximise internal validity by assuring rigorous control of all variables other than the intervention, and thus are often conducted in large tertiary care, referral-based health centres on a homogeneous group of patients, who have demonstrated compliance, are likely to remain in the study and often have no medical condition other than the one under treatment. Explanatory trials test whether a therapy can work; pragmatic trials (see there) test whether a therapy does in fact work, by managing patients in the real world.
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For the reader it may be helpful to think of a sliding scale, moving from a highly controlled explanatory trial to a clinically-orientated pragmatic trial.
After development and initial testing the first clinical study should be an explanatory trial.
MacRae KD (1989): Pragmatic versus explanatory trials.
Table 2 Summary of common features of pragmatic and explanatory trials Explanatory Pragmatic Often experimental Routine clinical environment setting Evaluation of Comparison of effectiveness efficacy Placebo controlled Not placebo controlled Control of non- Non-specific effects accepted specific treatment as part of normal clinical effects practice May be better May be better suited to suited to acute chronic conditions conditions Patients and Patients and practitioners not practitioners usually blinded, however allocation to blinded groups should be concealed, and the assessor of outcomes should be blinded to group allocation.
Dealing with the Data--In explanatory trials patients who do not adhere to the treatment protocol are often excluded from analysis.
Why are pragmatic trials generally more suitable than explanatory trials in the assessment of physiotherapy interventions?
Many however, may be less familiar with the two principal forms of randomised clinical trial: pragmatic trials and explanatory trials.
Explanatory trials deal with efficacy, whereas pragmatic trials are more closely associated with effectiveness.
Generally, the tight controls of explanatory trials lead to maximal internal validity but as a result external validity may suffer.
Most of our current data on the use of hormones for rising PSA are derived from explanatory trials.