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Table 4 Explanatory and practical clinical trials: Two options for clinical trials in community settings [7, 42]

From: Bridging the gap between basic science and clinical practice: a role for community clinicians

  Explanatory clinical trials: Practical clinical trials:
Hypothesis and design Hypothesis and study questions are designed to improve the understanding of the mechanism by which an intervention works Hypothesis and study questions are designed to facilitate decision making
Research question How effective is a treatment under ideal, experimental conditions? How effective is a treatment in every-day practice? What are the risks, benefits, and costs in every-day practice?
Defining the patient sample Rigorous inclusion/exclusion criteria to create a well-defined, homogenous sample of patients Wide inclusion/exclusion criteria to reflect actual, often diverse, patient populations in clinical practices
Practice setting Homogeneous Many and diverse
Intervention Well-specified, precise protocol with limited variation allowed; often involves treatment vs. placebo Well-specified, precise protocol allowing variation in implementation from site to site to capture actual patient and care characteristics; often compares existing, clinically-relevant, feasible treatment alternatives (often head-to-head)
Adequate sample size Enough to assemble a homogenous group that will enable a study of a relationship between a single intervention and a dominant outcome measure Often requires large sample size to account for heterogeneity in sample and long-term nature of studies
Outcome Well-defined; often a specific biological effect of an intervention Often defined broadly in relation to patient's function or quality of life so effect sizes on personal and population health can be calculated