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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After development and initial testing the first clinical study should be an explanatory trial. If the treatment is found to be efficacious it should then be assessed for effectiveness in a pragmatic trial (Helms 2002, Sheikh et al 2002).
Many however, may be less familiar with the two principal forms of randomised clinical trial: pragmatic trials and explanatory trials. This article aims to clarify these two research designs and explain why pragmatic designs are generally better suited to the assessment of physiotherapy interventions.
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.
Participants--As pragmatic trials aim to test a treatment approach in a normal clinical environment their participants tend to be more heterogeneous than in explanatory trials (Helms 2002).
Dealing with the Data--In explanatory trials patients who do not adhere to the treatment protocol are often excluded from analysis.
MacRae KD (1989): Pragmatic versus explanatory trials. International Journal of Technology Assessment in Health Care 5: 333-339.
Explanatory trials are designed to find out whether a treatment has any efficacy (usually compared with placebo) under ideal, experimental conditions [13].
Most of our current data on the use of hormones for rising PSA are derived from explanatory trials. There have been some case reports of patients with rising PSA who were given some form of hormone therapy to lower it.
Where outcome measurement is used to evaluate a service intervention in a pragmatic trial, it is preferable to choose a single measure as the end-point for decision-making, although multiple end-points can be used in explanatory trials [19].
Pragmatic and explanatory trials in the evaluation of the experimental National Health Service nursing homes.