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ABSTRACT
Objectives
In stepped-wedge cluster randomized trials (SW-CRTs), clusters are randomized not
to treatment and control arms, but to sequences dictating the times of crossing from
control to intervention conditions. Randomization is an essential feature of this
design but application of standard methods to promote and report on balance at baseline
are not straightforward. We aimed to describe current methods of randomization and
reporting of balance at baseline in SW-CRTs.
Study Design and Setting
We used electronic searches to identify primary reports of SW-CRTs published between
2016 and 2022.
Results
Across 160 identified trials, the median number of clusters randomized was 11 (Q1-Q3:
8-18). Sixty-three (39%) used restricted randomization — most often stratification
based on a single cluster-level covariate; 12 (19%) of these adjusted for the covariate(s)
in the primary analysis. Overall, 50 (31%) and 134 (84%) reported on balance at baseline
on cluster- and individual-level characteristics, respectively. Balance on individual-level
characteristics was most often reported by condition in cross-sectional designs and
by sequence in cohort designs. Authors reported baseline imbalances in 72 (45%) trials.
Conclusion
SW-CRTs often randomize a small number of clusters using unrestricted allocation.
Investigators need guidance on appropriate methods of randomization and assessment
and reporting of balance at baseline.
Keywords
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Article info
Publication history
Accepted:
March 13,
2023
Received in revised form:
March 9,
2023
Received:
January 12,
2023
Publication stage
In Press Journal Pre-ProofFootnotes
The authors declare that they have no conflicts of interest related to this article.
Identification
Copyright
© 2023 Elsevier Inc. All rights reserved.
