Abstract
BackgroundStepped wedge randomised trial designs involve sequential roll-out of an intervention to participants (individuals or clusters) over a number of time periods. By the end of the study, all participants will have received the intervention, although the order in which participants receive the intervention is determined at random. The design is particularly relevant where it is predicted that the intervention will do more good than harm (making a parallel design, in which certain participants do not receive the intervention unethical) and/or where, for logistical, practical or financial reasons, it is impossible to deliver the intervention simultaneously to all participants. Stepped wedge designs offer a number of opportunities for data analysis, particularly for modelling the effect of time on the effectiveness of an intervention. This paper presents a review of 12 studies (or protocols) that use (or plan to use) a stepped wedge design. One aim of the review is to highlight the potential for the stepped wedge design, given its infrequent use to date.MethodsComprehensive literature review of studies or protocols using a stepped wedge design. Data were extracted from the studies in three categories for subsequent consideration: study information (epidemiology, intervention, number of participants), reasons for using a stepped wedge design and methods of data analysis.ResultsThe 12 studies included in this review describe evaluations of a wide range of interventions, across different diseases in different settings. However the stepped wedge design appears to have found a niche for evaluating interventions in developing countries, specifically those concerned with HIV. There were few consistent motivations for employing a stepped wedge design or methods of data analysis across studies. The methodological descriptions of stepped wedge studies, including methods of randomisation, sample size calculations and methods of analysis, are not always complete.ConclusionWhile the stepped wedge design offers a number of opportunities for use in future evaluations, a more consistent approach to reporting and data analysis is required.
Highlights
Stepped wedge randomised trial designs involve sequential roll-out of an intervention to participants over a number of time periods
Randomised Controlled Trials (RCTs) are considered the 'Gold Standard' test of clinical effectiveness [1] and such trials are increasingly being used in evaluations of nonclinical interventions
An example of the logistics of a stepped wedge trial design is shown in Figure 1, which shows a stepped wedge design with five steps
Summary
Stepped wedge randomised trial designs involve sequential roll-out of an intervention to participants (individuals or clusters) over a number of time periods. In a stepped wedge design, an intervention is rolled-out sequentially to the trial participants (either as individuals or clusters of individuals) over a number of time periods. Regions Workplace GP surgeries Houses in Watcombe Sexual health clinic Health clinics Ambulatory care clinic in a tertiary hospital NHS hospital trust Households Company health centre National rehabilitation units HIV clinics tion plans emerging as the most common interventions Such interventions are likely to have an existing evidence base, adding to intuitive beliefs that the intervention is likely to do more good than harm. It is only permissible to include terminal end-points (such as death) in studies with a repeated cross-sectional design: in individual/
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