Study designs for effectiveness and translation research :identifying trade-offs.

Background: Practitioners and policymakers need credible evidence of effectiveness to justify allocating resources to complex, expensive health programs. Investigators, however, face challenges in designing sound effectiveness and translation research with relevance for "real-world" settings.
Methods: Research experts and federal and foundation funders (n= approximately 120) prepared for and participated in a symposium, held May 4-5, 2004, to weigh the strengths, limitations, and trade-offs between alternate designs for studying the effectiveness and translation of complex, multilevel health interventions.
Results: Symposium attendees acknowledged that research phases (hypothesis generating, efficacy, effectiveness, translation) are iterative and cyclical, not linear, since research in advanced phases may reveal unanswered questions in earlier phases. Research questions thus always need to drive the choice of study design. When randomization and experimental control are feasible, participants noted that the randomized controlled trial with individual random assignment remains the gold standard for safeguarding internal validity. Attendees highlighted trade-offs of randomized controlled trial variants, quasi-experimental designs, and natural experiments for use when randomization or experimental control or both are impossible or inadequately address external validity. Participants discussed enhancements to all designs to increase confidence in causal inference while accommodating greater external validity. Since no single study can establish causality, participants encouraged replication of studies and triangulation using different study designs. Participants also recommended participatory research approaches for building population relevance, acceptability, and usefulness.
Conclusions: Consideration of the study design choices, trade-offs, and enhancements discussed here can guide the design, funding, completion, and publication of appropriate policy- and practice-oriented effectiveness and translational research for complex, multilevel health interventions.