Optimising a digitally delivered behavioural weight loss programme: study protocol for a factorial cluster randomised controlled trial.

BACKGROUND: Digitally delivered weight loss programmes can provide a convenient, potentially cheaper, and scalable treatment option for people who may need to lose weight. However, outcomes are often inferior to in-person interventions in the long-term. This trial will use principles from the Multiphase Optimisation Strategy (MOST) framework to test whether it can enhance the effectiveness of a commercial digital behavioural weight loss programme. This trial aims to identify an optimised combination of four intervention components to enhance weight loss over a 24-week period. We will also explore which components contribute to improvements in participant retention and engagement with the programme. METHODS: Approximately 1400 adults with a BMI > 21 kg/m2 will be enrolled and randomised to one of 16 experimental conditions in a 24 factorial cluster design. The trial will test four intervention components: an introductory video call with the health coach, drop-in webchat sessions with the health coach, goal setting statements, and food diary review and feedback. All participants will receive the core digital behavioural weight loss programme and up to four new intervention components. Participation in the trial will last for 24 weeks. The primary outcome will be weight change at 16 weeks. Other outcomes, measured at 4, 16, and 24 weeks, include programme drop-out and engagement (number of interactions with the three main app functions). Fidelity and acceptability will be assessed using data on component adherence and self-report questionnaires. Decision-making for the enhanced programme will be based on components that contribute to at least a minimal improvement in weight loss, defined as ≥ 0.75kg, alone or in combination with other components. DISCUSSION: The factorial design is an efficient way to test the efficacy of behavioural components alone, or in combination, to improve the effectiveness of digital weight loss programmes. This trial will test the implementation of the MOST framework in an industry setting, using routinely collected data, which may provide a better way to refine and evaluate these types of interventions in a model of continuous service improvement. TRIAL REGISTRATION: Trial registration: ISRCTN, ISRCTN14407868. Registered 5 January 2024, 10.1186/ISRCTN14407868.

Protocol for an evaluation of adherence monitoring and support interventions among people initiating antiretroviral therapy in Cape Town, South Africa-a multiphase optimization strategy (MOST) approach using a fractional factorial design.

BACKGROUND: South Africa bears a large HIV burden with 7.8 million people with HIV (PWH). However, due to suboptimal antiretroviral therapy (ART) adherence and retention in care, only 66% of PWH in South Africa are virally suppressed. Standard care only allows for suboptimal adherence detection when routine testing indicates unsuppressed virus. Several adherence interventions are known to improve HIV outcomes, yet few are implemented in routinely due to the resources required. Therefore, determining scalable evidence-based adherence support interventions for resource-limited settings (RLS) is a priority. The multiphase optimization strategy (MOST) framework allows for simultaneous evaluation of multiple intervention components and their interactions. We propose to use MOST to identify the intervention combination with the highest levels of efficacy and cost-effectiveness that is feasible and acceptable in primary care clinics in Cape Town. METHODS: We will employ a fractional factorial design to identify the most promising intervention components for inclusion in a multi-component intervention package to be tested in a future randomized controlled trial. We will recruit 512 participants initiating ART between March 2022 and February 2024 in three Cape Town clinics and evaluate acceptability, feasibility, and cost-effectiveness of intervention combinations. Participants will be randomized to one of 16 conditions with different combinations of three adherence monitoring components: rapid outreach following (1) unsuppressed virus, (2) missed pharmacy refill collection, and/or (3) missed doses as detected by an electronic adherence monitoring device; and two adherence support components: (1) weekly check-in texts and (2) enhanced peer support. We will assess viral suppression (<50 copies/mL) at 24 months as the primary outcome; acceptability, feasibility, fidelity, and other implementation outcomes; and cost-effectiveness. We will use logistic regression models to estimate intervention effects with an intention-to-treat approach, employ descriptive statistics to assess implementation outcomes, and determine an optimal intervention package. DISCUSSION: To our knowledge, ours will be the first study to use the MOST framework to determine the most effective combination of HIV adherence monitoring and support intervention components for implementation in clinics in a RLS. Our findings will provide direction for pragmatic, ongoing adherence support that will be key to ending the HIV epidemic. TRIAL REGISTRATION: ClinicalTrials.gov NCT05040841. Registered on 10 September 2021.