Search

Background Three arguments are usually invoked in favour of stepped wedge cluster randomised controlled trials: the logistic convenience of implementing an intervention in phases, the ethical benefit of providing the intervention to all clusters, and the potential to enhance the social acceptability of cluster randomised controlled trials. Are these alleged benefits real? We explored the logistic, ethical, and political dimensions of stepped wedge trials using case studies of six recent evaluations. Methods We identified completed or ongoing stepped wedge evaluations using two systematic reviews. We then purposively selected six with a focus on public health in high, middle, and low-income settings. We interviewed their authors about the logistic, ethical, and social issues faced by their teams. Two authors reviewed interview transcripts, identified emerging issues through qualitative thematic analysis, reflected upon them in the context of the literature, and invited all participants to co-author the manuscript. Results Our analysis raises three main points. First, the phased implementation of interventions can alleviate problems linked to simultaneous roll-out, but also brings new challenges. Issues to consider include the feasibility of organising intervention activities according to a randomised sequence, estimating time lags in implementation and effects, and accommodating policy changes during the trial period. Second, stepped wedge trials, like parallel cluster trials, require equipoise: without it, randomising participants to a control condition, even for a short time, remains problematic. In stepped wedge trials, equipoise is likely to lie in the degree of effect, effectiveness in a specific operational milieu, and the balance of benefit and harm, including the social value of better evaluation. Third, the strongest arguments for a stepped wedge design are logistic and political rather than ethical. The design is advantageous when simultaneous roll-out is impractical and when it increases the acceptability of using counterfactuals. Conclusions The logistic convenience of phased implementation is context-dependent, and may be vitiated by the additional requirements of phasing. The potential for stepped wedge trials to enhance the social acceptability of cluster randomised trials is real, but their ethical legitimacy still rests on demonstrating equipoise and its configuration for each research question and setting.

The stepped wedge design, under which all trial participants receive the intervention but the order in which the intervention is received is randomised, is potentially useful to rigorously evaluate organisational interventions to improve quality and safety. We use two examples of cluster-randomised stepped-wedge trials (DQIP and GP-POLY) to illustrate advantages and disadvantages of the design in evaluations of complex prescribing improvement interventions in primary care. DQIP is nearing completion and GP-POLY will start in 2013. The intervention in both DQIP and GP-Poly involves outreach visits by researchers for education and informatics tool training, making sequential roll out a logistic necessity. The stepped wedge allows for this by design, but trial durations may be prolonged compared to parallel-arm trials and other designs, and arranging initiation visits to fit with randomisation schedules is challenging. Since all participants receive the intervention and there are multiple repeated measurements, practice sample size requirements in DQIP and GP-POLY were reduced compared to a parallel-arm design, but power calculations are more complex. Recruitment may be improved by offering the intervention to all participants, but creates potential problems for retention and avoiding contamination in practices with long lags between recruitment and intervention start. Because of the vulnerability of stepped wedge trials to time varying confounding, avoiding changes in intervention delivery to successive cohorts is important and needs careful planning. The stepped wedge design is attractive for cluster randomised trials of quality improvement interventions, especially when staggering of intervention delivery is inevitable, but presents challenges for implementation that need careful planning. Oral presentation presented at the 2nd Clinical Trials Methodology Conference 2013: Methodology matters, 18-19 November 2013, Edinburgh, UK.

Process evaluations are recommended to open the 'black box' of complex interventions evaluated in trials, but there is limited guidance to help with design, with most guidance focused on the use of qualitative methods rather than processes to evaluate. We have developed a framework that identifies a range of candidate processes that an evaluation could examine to understand clusterrandomised intervention implementation and maintenance. These include processes involving clusters (recruitment, delivery of the intervention to the cluster, adoption by the cluster), involving the individuals on whom outcomes are measured (reach, delivery of the intervention to the individual, response of the individual), maintenance, and unintended consequences. Researchers will often have to choose what to focus on because of resource constraints, the framework aims to help researchers make explicit their choices of research questions and methods. We will illustrate application of the framework to the design and conduct of a parallel process evaluation of the Data-driven Quality Improvement in Primary Care trial, which evaluates a complex intervention to improve prescribing safety in 40 general practices. This mixed method process evaluation includes a dominant case study approach in a purposeful sample of practices and hypothesis?testing quantitative analysis of data from all practices examining how key processes are associated with variation in outcome between practices. We will present analysis of qualitative data from the 10 case study practices participating (6 reducing and 4 not reducing targeted prescribing), and focus groups with patients who have had their medication changed as a result of the intervention. Oral presentation presented at the 2nd Clinical Trials Methodology Conference 2013: Methodology matters, 18-19 November 2013, Edinburgh, UK.