Explanatory trials v
pragmatic trials from the 3rd edition of
Clinical EpidemiologyPragmatic RCT’s are reliable evaluations of health care
effectiveness carried out under real world conditions. Although there
is a recent upsurge of interest in pragmatic trials, led, amongst
others by the Practihc group, the best descriptions of these trials are
20 years old. (Schwartz, D., Lelouch, J. Explanatory and
pragmatic attitudes in therapeutic trials. Journal of Chronic Disease
1967; 20: 637-648).
Classic explanatory randomised trials (efficacy trials) test the
effects, under idealised and tightly controlled conditions, of
precisely characterised and specified treatments, on narrowly defined
groups of individual patients. The effects may be assessed
by the impact on physiological or chemical parameters, and the purpose
is mainly to advance biomedical knowledge. Pragmatic trials, by
contrast are concerned with assessing the effects of
interventions as they are usually used, in typical settings, and on
typical users. The units studied may be hospital wards, clinics, health
districts or other groups, as well as individual patients,
practitioners or community members. Effectiveness of the intervention
is usually assessed by impact on simple outcomes of importance to users
of the intervention such as death, major disability, user satisfaction,
cost and quality of care, and quality of life.
Pragmatic trials are more interesting to policymakers than efficacy
trials. Pragmatic trials are attuned to the same criteria of
effectiveness as those used by policymakers – namely user perceptions,
important and visible outcomes, usual health service planning
entities, and typical service limitations. Pragmatic trials take into
account the varied ways that interventions are implemented in the real
world.
Explanatory trials v
pragmatic trials from the 3rd edition of
Clinical EpidemiologyDave Sackett has written a good explanation of the difference between explanatory trials and pragmatic trials. The text was prepared it for the forthcoming 3rd edition of Clinical Epidemiology; A Basic Science for Answering Questions about Health Care, to be published by Lippincott, Williams & Wilkins in 2005.