Assessing the value for money, from a policy maker perspective, of 24 randomised controlled trial designs for an...

To analyse whether conducting a randomised controlled trial (RCT) to evaluate an online weight maintenance guided self-help intervention (Supporting Weight Management (SWiM)) would offer good value for money in the United Kingdom.

We examined 24 RCT designs by varying inclusion criteria (participants completing behavioural weight management, specialist-led weight management, diabetes prevention programme, type 2 diabetes remission, digital weight management, all weight management services), trial duration (1-2 years), and sample size (n = 500 or 2000). Trial benefits were estimated by the method of expected value of sample information analysis using a health economic model. The model examines how the proposed intervention affects weight maintenance over time (with uncertainty), and generates estimated lifetime Quality Adjusted Life Years (QALYs) and National Health Service (NHS) costs. Structured expert elicitation with 4 experts was undertaken to quantify pre-trial uncertainty in the effectiveness of SWiM compared with usual care. All trial designs were simulated to estimate trial benefits: the reduction in the costs of an inefficient decision for future populations over 10 years. Trial designs offer value for money if trial benefits exceed trial costs.

For three inclusion criteria options (groups recently completing 'diabetes remission', 'digital weight management' or 'specialist weight management'), the cost of the proposed trials was estimated to exceed the estimated trial benefit (value of the reduction in decision uncertainty) over 10 years. For the other three inclusion criteria options (groups recently completed 'behavioural weight management', 'diabetes prevention programme', or 'all weight loss programmes'), 12 trial designs produced greater benefits than costs. The optimal trial design option would include 'all weight loss programmes', with 2 years follow-up and sample size n = 2000.

Investment in a large RCT to evaluate the SWiM intervention for patients completing a range of weight loss interventions offers the greatest value to the NHS.