Factors influencing use and choice of Core Outcome Sets and Outcome Measurement Instruments in trials of interventions to prevent childhood obesity: a mixed-methods survey

Background and objective: Heterogeneity in what and how outcomes are measured in childhood obesity prevention trials limits evidence synthesis and evaluation of intervention effectiveness. Core Outcome Sets (COS) and Core Outcome Measurement Sets (COMS) can standardize measurement and reporting across trials, but only if they are used by trialists. This study examined trialists' awareness and attitudes toward two childhood obesity-related COS and factors influencing their use; characteristics of Outcome Measurement Instruments (OMIs) used in childhood obesity prevention trials; and how trialists choose these OMIs. Methods: An online, international, cross-sectional survey was conducted including trialists engaged in designing and/or conducting childhood obesity prevention trials in children aged 0-5 years. Trialists were recruited via peer-reviewed publications, the Transforming Obesity Prevention for CHILDren Collaboration and professional contacts. The survey examined trialist characteristics, awareness, and use of existing COS, OMI characteristics, and factors influencing trialist selection of OMIs. Quantitative data were analyzed descriptively; qualitative data were analyzed using content analysis. Results: The majority of the 46 trialists who completed the survey were senior-career researchers (61%; n = 28), with 1 to 38 years' experience in childhood obesity prevention trials. Seventy percent (n = 32) were familiar with COS in general; 84% (n = 26) of these were familiar with one or both childhood obesity-related COS. These trialists' COS use was limited by perceived participant burden, cost, and lack of knowledge; availability of guidelines, and resources facilitated COS use. Trialists favored measuring outcomes using existing (83%; n = 38) and adapted (80%; n = 37) questionnaires, and anthropometric measures (80%; n = 37). Quantitative and qualitative data indicated that measurement properties (eg, reliability, validity), cost, perceived burden, ease of use, and feasibility were the most important factors influencing trialists' OMI choice. Conclusion: Trialists' awareness and use of childhood obesity-related COS is positive, and may be enhanced through provision of guidance and resources to support COS and COMS use. Development of COMS should consider trialist-reported factors related to feasibility and measurement properties. Such considerations can enhance COS and COMS use in trials, reducing outcome heterogeneity, and improving evaluation of intervention effectiveness to prevent childhood obesity.