Stepped wedge cluster randomized trials present advantages, challenges

American Academy of Family Physicians

The Stepped Wedge Cluster Randomized Trial is a research methodology that has been growing in popularity, particularly for pragmatic implementation and dissemination trials. SW-CRTs can have advantages over parallel cluster randomized trials with regards to statistical power. Clusters, such groups of physicians working together in a practice rather than individual physicians, are randomized to a sequence, which determines when—not if—they receive the intervention, which makes this design appealing and relevant for quality improvement and practice transformation initiatives. They also offer a pragmatic approach to providing the intervention to all practices.

Researchers interviewed investigators who conducted cluster randomized trials as part of the EvidenceNOW: Advancing Heart Health Initiative, one of the largest practice-improvement primary care studies funded by the Agency for Healthcare Research and Quality. All interviewees reported that SW-CRT can be an effective study design for large-scale intervention implementations. Advantages include: (1) incentivized recruitment, (2) staggered resource allocation and (3) statistical power. Challenges included: (1) time-sensitive recruitment, (2) retention, (3) randomization requirements and practice preferences, (4) achieving treatment schedule fidelity, (5) intensive data collection, (5) Hawthorne effect (sites modifying their behavior when made aware that they are being observed), and (7) changes that may occur in primary care clinics over time not associated with an intervention implementation.

The challenges experienced by EvidenceNOW grantees suggest that certain favorable, real-world conditions can increase the odds of a successful SW-CRT. Existing infrastructure can support the recruitment of many practices. Strong retention plans are needed to continue to engage sites waiting to start the intervention. Finally, study outcomes should be ones already captured in routine practice—otherwise, funders and investigators should assess the feasibility and cost of data collection.

Considerations Before Selecting a Stepped-Wedge Cluster-Randomized Trial Design for a Practice Improvement Study

Ann M. Nguyen, PhD, MPH, et al

Rutgers University, Center for State Health Policy, New Brunswick, New Jersey

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