Update to Trial Forge Guidance 2: addition of the Value of Information criterion.

Trial Forge Guidance 2 helps trial teams decide if another Study Within A Trial (SWAT) is needed to answer an existing research question. Five criteria are listed to assist decision-making. We are adding a sixth criterion, the Value of Information, to additionally consider the potential time and financial constraints of improving trial process evidence. The Value of Information criterion assesses each trial process based on its value of additional research and value of implementation. We consider evaluations of recruitment and retention strategies as exemplars of how such an approach could be applied to randomised evaluations of trial processes via SWATs. We applied the Value of Information Analysis to all recruitment strategies and categorised them according to their expected benefits in terms of improved recruitment, as well as the level of statistical uncertainty compared to other recruitment strategies. The same approach was followed for retention strategies. To support its use, we have developed an electronic tool that calculates and presents the criterion results for each available evaluation of recruitment and retention strategies. This will enable trial teams to apply the Value of Information criterion, along with the five existing criteria of Trial Forge Guidance 2, when deciding if further SWATs should be prioritised for a particular trial process strategy to provide evidence for the strategy's use, or not during a trial.