The stepped wedge cluster randomized trial and its potential for child health services research: a narrative review

Clinical Trials for Special Populations: Children, Older Adults, and Rare Diseases

Research cannot maximize population health unless it improves health for all members of the public, including special populations such as children, older adults, and people living with rare diseases. Each of these categories require special considerations when planning and performing clinical trials, and common threads of ethical conduct of research in vulnerable populations appear throughout. In this review, definitions of each of the three categories of special population (children, older adults, and rare diseases) are discussed in terms of US research regulations, the unique challenges to conducting clinical trials for these special populations, critical ethical issues, and opportunities for innovative ways to design and operationalize clinical trials in special populations. Additional critical attention is focused on factors that influence the generalizability of study results to reduce health disparities, as well as the importance of community engagement and advocacy groups that can help to educate potential trial participants of the benefits of clinical trial participation.

Bikes for Life: Measuring the effects of a bicycle distribution program on 6 to 12-year-old children's BMI and health behaviors

Treating pediatric obesity is challenging. The objective was to evaluate effect of receiving a bicycle on (a) physical activity, (b) sedentary activity, (c) Body Mass Index (BMI), and (d) eating habits. A stepped-wedge randomized controlled trial of 6- to 12-year-old patients with overweight/obesity was conducted April 2012-2018. Participants were randomized to wait 0, 2, 4, or 6 months for a bicycle. Outcomes on activity, BMI and eating were collected at 3, 6, 9- and 12-months after children received a bicycle. A total of 525 participants with 387 (74%) completed 3-month follow-up questionnaire, and 346 (66%) completed 12-month follow-up visit. Participants were mostly Latino/a (71%) and low income (58%), and 31% had never ridden a bicycle. Median baseline BMI was 98th percentile. At 3 months, 62% reported bicycle use last week, on average 3.6 days. Time spent on sedentary activities decreased by 48 min/day (p = 0.04), and time spent playing sports increased by 1.7 h/week (p < 0.01). No reduction in BMI was seen. Consumption of sugary drinks decreased (by 0.59 servings/week, p < 0.01), and consumption of vegetables increased (0.71 servings/week, p = 0.04). At 12 months, sedentary time, sugary drink and vegetable consumption remained significantly more favorable than at enrollment (p < 0.01, p < 0.01, p = 0.04 respectively), but not significantly different (p = 0.47 for sedentary, p = 0.73 for sugary drink) and significantly less favorable (p < 0.01 for vegetables) than at the time of intervention. Participants reported riding bicycle, improved activity and dietary habits, though reversion towards baseline behavior was seen by one year and no change in BMI from enrollment.

Unique Challenges of Randomised Controlled Trials in Pediatric Cardiology

Pediatric cardiology has evolved over time with reductions in childhood mortality due to congenital heart disease. Surgical innovation drove early changes in care. Increasingly, the need for more robust evidence provided by randomised controlled trials (RCTs) has been recognised. Although the number of RCTs has increased, there remains a relative paucity of truly impactful trials in the field. However, those trials that have changed practice have demonstrated the potential and importance of this work. Examples include the PRIMACORP trial, which established the safety and efficacy of milrinone after cardiac surgery, and the Single Ventricle Reconstruction trial, which was the first multicentre pediatric cardiac surgical RCT. The successful conduct and important findings emanating from these trials serve as beacons as clinicians strive to improve the evidence base in this field. The establishment of national and international networks such as the Pediatric Heart Network and the Canadian Pediatric Cardiology Research Network provide a strong foundation for future collaborative work. Despite this progress, there remain important challenges to designing and executing RCTs in pediatric cardiology. These include issues of greater disease and patient heterogeneity and increased costs. The use of innovative study designs and analytic methods and the establishment of core outcome measures have the potential to overcome some of the issues related to the smaller patient numbers compared with adult disciplines. As pediatric cardiologists look to the future, it is imperative that we work together to derive the maximum benefit from the considerable efforts directed toward conducting impactful clinical trials in pediatric cardiology.

Variations in stepped-wedge cluster randomized trial design: Insights from the Patient-Centered Care Transitions in Heart Failure trial

The stepped-wedge (SW) cluster randomized controlled trial, in which clusters cross over in a randomized sequence from control to intervention, is ideal for the implementation and testing of complex health service interventions. In certain cases however, implementation of the intervention may pose logistical challenges, and variations in SW design may be required. We examine the logistical and statistical implications of variations in SW design using the optimization of the Patient-Centered Care Transitions in Heart Failure trial for illustration. We review the following complete SW design variations: a typical SW design; an SW design with multiple clusters crossing over per period to achieve balanced cluster sizes at each step; hierarchical randomization to account for higher-level clustering effects; nested substudies to measure outcomes requiring a smaller sample size than the primary outcomes; and hybrid SW design, which combines parallel cluster with SW design to improve efficiency. We also reviewed 3 incomplete SW design variations in which data are collected in some but not all steps to ease measurement burden. These include designs with a learning period that improve fidelity to the intervention, designs with reduced measurements to minimize collection burden, and designs with early and late blocks to accommodate cluster readiness. Variations in SW design offer pragmatic solutions to logistical challenges but have implications to statistical power. Advantages and disadvantages of each variation should be considered before finalizing the design of an SW randomized controlled trial.

Delaying and withholding interventions: ethics and the stepped wedge trial

Ethics has been identified as a central reason for choosing the stepped wedge trial over other kinds of trial designs. The potential advantage of the stepped wedge design is that it provides all arms of the trial with the active intervention over the course of the study. Some groups receive it later than others, but the study intervention is not withheld from any group. This feature of the stepped wedge design seems particularly ethically advantageous in two instances: (1) when the study intervention appears especially likely to be effective and (2) when the consequences of not receiving the intervention may be dire. But despite an increase in the use of the stepped wedge design and appeals to its ethical superiority as the motivation for its selection, there has been limited attention to the stepped wedge trial in the ethics literature. In the following, I examine whether there are persuasive ethical reasons to prefer or to require a stepped wedge trial. I argue that while the stepped wedge design is ethically permissible, it is not morally superior to other kinds of trials. To this end, I examine the ethical justification for providing, withholding, and delaying interventions in research.

Evaluating the impact of multilevel evidence-based implementation strategies to enhance provider recommendation on human papillomavirus vaccination rates among an empaneled primary care patient population: a study protocol for a stepped-wedge cluster randomized trial

Background

Each year, human papillomavirus (HPV) causes 30,000 cancers in the USA despite the availability of effective and safe vaccines. Uptake of HPV vaccine has been low and lags behind other adolescent vaccines. This protocol describes a multilevel intervention to improve HPV vaccination rates.

Methods

Using a cluster randomized trial, we will evaluate the independent and combined impact of two evidence-based implementation strategies with innovative enhancements on HPV vaccination rates for female and male patients. The clusters are six primary care sites providing care to pediatric populations. We will use a stepped-wedge cluster randomized design, including process evaluation, to test the hypothesis that compared with the current course of care and a practice-level intervention using reminder-recall interventions coupled with provider-level audit and feedback with education increases HPV vaccination rates in exposed clusters. The factorial design allows us to use a single trial to test these two interventions and to assess each individually and in combination. Our design has four 12-month steps. The first step will be a baseline period; data collected during it will provide a within-practice control group for each cluster. Second, two clusters will be randomly assigned to receive intervention 1 (reminder and recall), and two clusters will be randomly selected to receive intervention 2 (audit and feedback with education). Third, the other two clusters will be randomly allocated to intervention 1 or 2. Clusters initially with intervention 1 will be randomly allocated to 1 + 2 or 1; clusters initially with intervention 2 will be randomly allocated to 1 + 2 or 2. Fourth, all clusters will receive both interventions. To ensure balance of patient numbers across interventions, we will use block randomization at the first step, with the six clusters grouped into three pairs according to volume. Our primary outcome will be vaccination rates.

Discussion

Results of our clinical trial and process evaluation will provide evidence showing whether practice- and provider-level interventions improve HPV vaccination rates and will offer insight into contextual factors associated with direction and magnitude of trial outcomes.

Trial registration

ClinicalTrials.gov, NCT03501992, registered April 18, 2018.

Electronic supplementary material

The online version of this article (10.1186/s13012-018-0778-x) contains supplementary material, which is available to authorized users.

Stepped wedge cluster randomised trials: a review of the statistical methodology used and available

BACKGROUND

Previous reviews have focussed on the rationale for employing the stepped wedge design (SWD), the areas of research to which the design has been applied and the general characteristics of the design. However these did not focus on the statistical methods nor addressed the appropriateness of sample size methods used.This was a review of the literature of the statistical methodology used in stepped wedge cluster randomised trials.

METHODS

Literature Review. The Medline, Embase, PsycINFO, CINAHL and Cochrane databases were searched for methodological guides and RCTs which employed the stepped wedge design.

RESULTS

This review identified 102 trials which employed the stepped wedge design compared to 37 from the most recent review by Beard et al. 2015. Forty six trials were cohort designs and 45 % (n = 46) had fewer than 10 clusters. Of the 42 articles discussing the design methodology 10 covered analysis and seven covered sample size. For cohort stepped wedge designs there was only one paper considering analysis and one considering sample size methods. Most trials employed either a GEE or mixed model approach to analysis (n = 77) but only 22 trials (22 %) estimated sample size in a way which accounted for the stepped wedge design that was subsequently used.

CONCLUSIONS

Many studies which employ the stepped wedge design have few clusters but use methods of analysis which may require more clusters for unbiased and efficient intervention effect estimates. There is the need for research on the minimum number of clusters required for both types of stepped wedge design. Researchers should distinguish in the sample size calculation between cohort and cross sectional stepped wedge designs. Further research is needed on the effect of adjusting for the potential confounding of time on the study power.

The need to balance merits and limitations from different disciplines when considering the stepped wedge cluster randomized trial design

Background

Various papers have addressed pros and cons of the stepped wedge cluster randomized trial design (SWD). However, some issues have not or only limitedly been addressed. Our aim was to provide a comprehensive overview of all merits and limitations of the SWD to assist researchers, reviewers and medical ethics committees when deciding on the appropriateness of the SWD for a particular study.

Methods

We performed an initial search to identify articles with a methodological focus on the SWD, and categorized and discussed all reported advantages and disadvantages of the SWD. Additional aspects were identified during multidisciplinary meetings in which ethicists, biostatisticians, clinical epidemiologists and health economists participated. All aspects of the SWD were compared to the parallel group cluster randomized design. We categorized the merits and limitations of the SWD to distinct phases in the design and conduct of such studies, highlighting that their impact may vary depending on the context of the study or that benefits may be offset by drawbacks across study phases. Furthermore, a real-life illustration is provided.

Results

New aspects are identified within all disciplines. Examples of newly identified aspects of an SWD are: the possibility to measure a treatment effect in each cluster to examine the (in)consistency in effects across clusters, the detrimental effect of lower than expected inclusion rates, deviation from the ordinary informed consent process and the question whether studies using the SWD are likely to have sufficient social value. Discussions are provided on e.g. clinical equipoise, social value, health economical decision making, number of study arms, and interim analyses.

Conclusions

Deciding on the use of the SWD involves aspects and considerations from different disciplines not all of which have been discussed before. Pros and cons of this design should be balanced in comparison to other feasible design options as to choose the optimal design for a particular intervention study.