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.
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 .
Pragmatic and explanatory trials in the evaluation of the experimental National Health Service nursing homes.