Methodological development for core outcome sets in population health research: a mixed-methods study

Core outcome sets (COS) aid evidence synthesis and promote relevance of and reduce waste from trials. COS are commonly used in biomedical research settings, but their application in population health research is less established. There is growing interest in using COS in population health trials, but population health interventions are often complex and involve a wide range of stakeholders, differing from biomedical research. Current guidance for COS development was originally intended for effectiveness trials in biomedical research, and COS implementation in trials is limited. This exploratory research formulates COS methodology for use in population health research trials, identifies priority topics for COS development, and considers how to promote COS use once developed.

Three mixed-method work packages (WP) are as follows: (1) Public health evidence review to identify outcome heterogeneity and reporting of indicators of inequality and disadvantage, (2) stakeholder data review of COS on the Core Outcome Measures in Effectiveness Trials Initiative database and National Institute for Health and Care Excellence (NICE) public health guidance, and (3) semi-structured focus group discussions via an expert workshop exploring how routinely collected data can be considered in population health core outcome sets, differences in population health research that COS methodology would need to accommodate, barriers and facilitators to COS uptake applicable to population health research, and areas of population health research that would benefit from COS development.

In WP1, 264 population health Cochrane reviews were identified and analysed. Eighty reviews recommended outcome standardisation, including 13 specifically recommending COS development. In WP2, 50 non-population health COS, 22 population health COS, and 61 NICE Public Health guidance documents used an average of 7, 4.7, and 6.1 stakeholder groups, respectively. The WP3 workshop involved 41 participants. Six themes (COS development, routine data collection, population health research, stakeholders, methodology, COS uptake) were identified. Five methodological recommendations were formulated.

This study proposes how COS should be developed for use in population health research, identifies areas for COS development, recommends COS implementation strategies for population health research trials, and explores novel applications of COS methodology such as to standardise routinely collected health and non-health data often used in population health trials. The study findings complement existing COS guidance, promoting a consistent and rigorous approach to COS development for use in population health trials.

This study was approved by the University of Birmingham Research Ethics Committee (ERN 21-1821) and registered at Research Registry (researchregistry7693, 28.02.2022).