1. Theme 2 Stepped wedge designs
Rieke van der Graaf PhD
GFBR Thailand 28 November 2017

2. Stepped wedge trial
A CRT crossover design in which clusters cross over in one direction only
All clusters start with the control treatment after which, at pre-specified time points, one or more clusters switch sequentially to the experimental intervention until eventually all clusters have received the new intervention

3. Cohort and cross-sectional SW CRTs
A. Cohort: same subjects within the clusters are being followed over time, hence the crossover between treatments is then not only at the cluster level but also at the subject level. B. Cross-sectional new subjects are being included after each step, which means that the crossover of treatments is only at the cluster level. In B not all participants will receive the intervention!

4. Specifics of SW CRTS
A stepped wedge trial = cluster randomized trial> same conditions apply
Morally relevant differences CRT and SW-CRTs? At least two
Clinical equipoise/delayed roll out
Social value (implementation or research?)
Esther de Hoop, Ingeborg van der Tweel, Rieke van der Graaf, Karel G. M. Moons, Johannes J. M. van Delden, Johannes B. Reitsma and Hendrik Koffijberg. The need to balance merits and limitations from different disciplines when considering the stepped wedge cluster randomized trial design. BMC Medical Research Methodology 2015, 15.

5. Equipoise and SWD
SWD is used a.o. in situations where an intervention under study “has shown to be effective in more controlled settings” (Mdege 2011) Or where there is “a prior belief that the intervention will do more good than harm, rather than a prior belief of equipoise” (Brown 2006)

6. What is social value of SWD?
Sufficient evidence about effectiveness of intervention > implement intervention
Room for performing SWD
Evidence needed to perform a SWD (more than one study)
No evidence about effectiveness of intervention> perform conventional RCT

7. Other ethics issues in this session
Gatekeeping
Informed consent
Identifying the research participant
Logistics and randomization