Table 2 Key advantages and challenges related to public health implementation in a stepped-wedge pragmatic CRCT

Stepped or staggered implementation

• Allows for the incremental introduction of the intervention or program.

• Multiple training and initiation must be undertaken at each step (or cluster crossover).

• The phased initiation is crucial to undertaking implementation across all 34 health centres all of which require individual training and monitoring which would not have been feasible in a full roll out or even a parallel CRCT.

• Multiple measurements is resource intensive throughout the entire study period during crossover or initiation and throughout all steps.

• Flexible design that can be modified for amount of steps and clusters based on need or manageability.

• Higher complexity in biostatistical analysis

• Higher quality evidence than observational and non-randomized pretest-posttest designs.

• All centers are intervention and controls.

Implementation in routine conditions

• The stepped-wedge study design allows for all partners to reach their specific goals and obtain the evidence they need from their perspective.

• Routine public health in LMICs is subject to many fiscal, political and programmatic pressures, however methodologic rigour is still required in this design and should be adhered to at least during the study period.

• The stepped-wedge pragmatic RCT is the most suited so all partners could benefit from high quality evidence, yet pragmatic utility.

• The design can be used to provide real world evidence of effectiveness by using a staggered implementation when a full population based intervention is planned. This allows for evidence that may not exist otherwise.

• Researchers had identified the major gaps in available high quality research evidence for the routine systematic evaluation of HCs of TB cases within the context of resource constrained TB endemic areas. In parallel, SJL district local NTP programmers had identified the urgent need to implement a program to actively evaluate HCs of TB cases undergoing treatment; there was a local programmatic concern of cases that were linked through familial or household contact, and the underperformance of their current passive approach for achieving screening of HCs.

• Researchers desire randomization, unbiased allocation of health centers.

• Data quality needs for research design may be above daily programmatic requirements (data quality control).

Overall Design

• Easy to integrate design, a modification of existing RCT and CRCT

• Methodological complexities to power and analyses of stepped-wedge designs

• Many of the authors of stepped-wedge design papers have contributed to the use and the methods for this design. On the other hand every study has its individual specific needs and we required specialized guidance in terms of the overall framework of the roll out, the frequency and duration of steps.

• Fewer experts with technical and practical experience using stepped-wedge designs

• RCT experts and methodologists widely available

• Because of its relatively recent use, published literature including many of the published stepped-wedge trial protocols in peer reviewed literature were relied upon.

• Unlike traditional individual randomized controlled trials and cluster randomized controlled trials, less is formally taught in research training and in operational training on the design and requirements for methodological rigour.

• The nomenclature is complex and could be confusing to stakeholder. Several terms have been used for the same design modification, including implementation trial, randomized start or staggered start trial, delayed designs, step or stepped-wedge designs amongst others [21, 22]

Longer trial length

• Focuses on a smaller subset of the intervention groups at time

• Population based intervention implementation requires programmatic and research supervision, throughout the duration of the entire study.

• As it is phased in, the monitoring, supervision and training can be improved and also any major problems, political, technical or resources can be identified to improve the implementation.

• Improves adherence by allowing for intensive monitoring and supervision of groups

• Longer trial period is also associated with increased intensity and duration of labour

• There are great challenges to sustaining monitoring efforts, in practice far more training and monitoring and supervision is required then initially estimated.

• Improves quality of training including smaller size of training groups and ability to integrate peer to peer support and hands on training in the field

• Research components can increase burden and the longer duration can lead to exhaustion for researchers, programmers and local health care staff.

Sample size/Power

• The stepped-wedge CRCT is considered to have higher power and precision with fewer clusters and increasing number of steps.

• In reality, the power, number of clusters and relative sample size is far more complex

• Achieving sample size and power in the design are not the major issue, however the study is limited to a fixed number of clusters and number of TB diagnosed cases within the NTP that occur during the study period

• The potential required power depends both on local requirements or existing fixed numbers of centres or patient populations.