Proposals for multi-outcome evaluations: insights from a systematic review and expert consultations

Abstract Systematic review insights: Our systematic review examined how researchers select, analyse, and interpret multiple outcomes, using digital interventions promoting health among adolescents and young adults as a study framework. We analysed 100 studies with 251 outcomes. Among the 26 interventions included, 7 defined a unique primary outcome, 10 used multiple primary outcomes, and 9 used non-hierarchised outcomes. We found important discrepancies in conclusions regarding intervention success: 35% of interventions deemed ‘successful’ by their original authors were reclassified as ‘non-conclusive’ by our team due to statistically conflicting results among outcomes, particularly in studies using non-hierarchised outcomes (70%). Expert consultation process: Building on these findings, we consulted with methodologists, health promotion specialists, and decision-makers to identify key challenges and potential solutions for multiple outcome evaluations. Consensus emerged around the need for standardised frameworks, transparent conclusion processes, and improved methodological reporting. Preliminary methodological proposals: Based on these insights and consultations, five methodological proposals were developed: 1. Developing core outcome sets tailored to health promotion interventions; 2. Establishing multidisciplinary steering committees for selecting and prioritising multiple outcomes; 3. Applying multiple criteria decision analysis and consensus-driven methods for transparent outcome combination; 4. Strengthening methodological reporting throughout intervention development and evaluation; 5. Increasing complex intervention experts’ involvement in ethics, funding, and evaluation committees. These proposals aim to enhance transparency, robustness, and trustworthiness in evaluating health promotion interventions with multiple outcomes. Further refinement and validation of these proposals during the proposed workshop will support their validity and facilitate their adoption in the field.