Understanding explanatory and pragmatic trials: Examples from randomized controlled trials on vertebroplasty.

OBJECTIVES: To better understand the explanatory-pragmatic distinction in the design and interpretation of randomized controlled trials (RCTs). METHODS: We review the explanatory-pragmatic distinction in clinical trial design. We use the PRECIS-2 tool to evaluate the trial design of selected RCTs on percutaneous vertebroplasty for osteoporotic vertebral compression fractures. We discuss difficulties in the selection of criteria and in the construction of PRECIS diagrams. We also examine how inconsistency in the selection of various items of trial design can cause confusion in the interpretation of results. RESULTS: The selection of criteria and the scoring of multiple PRECIS domains were subjective and thus debatable. The pragmascope patterns of various vertebroplasty trials were heterogeneous. Many trials had both pragmatic and explanatory components. Some placebo-controlled trial goals seem to have been explanatory, but their design actually included enough pragmatic items such that the meaning of negative trial results remains ambiguous. CONCLUSION: The results of a trial cannot be interpreted without understanding the various design choices made along the explanatory-pragmatic spectrum.

The "pragmatic trial": An essentially contested concept?

For over 50 years, clinical research methodology has wrestled with the problem of the lack of correspondence between tests of treatments and applications of treatments. The former comprise of trials featuring scrupulous control of patient eligibility, treatment compliance, clinician expertise, follow-up intensity, and so on. In applying a validated treatment, the practitioner has to confront considerable real-world variation in potential patients and in implementation regimes. The remedy, going by the name of "pragmatic trials," is to conduct clinical trials in conditions corresponding more closely to everyday practice. This solution has proved easier to utter than to execute, and the paper reviews the extensive literature on pragmatic trials, seeking to assess whether it has terminated in clarity or contestation.