Objectives Mediation analysis is a widely used quantitative method for investigating how interventions and exposures in randomised controlled trials and observational studies have an effect on healthcare outcomes. This study aimed to assess the importance of items that should be considered in a consensus meeting aimed at developing a guideline for reporting mediation analyses.
Design International online Delphi study.
Participants International experts in the development and application of mediation analysis.
Main outcome measures The Delphi panel were asked to rate the importance of a list of items for inclusion in a guideline for reporting mediation analyses. Thresholds for disagreement and consensus on importance for inclusion were specified a priori. We used the Research ANd Development/University of California Los Angeles appropriateness method to quantitatively assess the importance for inclusion and panel agreement.
Results Nineteen expert panellists (10 female) from seven countries agreed to participate. All panellists contributed to all three rounds conducted between 10 June 2019 and 6 November 2019. The panel reached consensus on 34 unique reporting items for study design, analytic procedures and effect estimates, with three items rated ‘optional’. Panellists added one extra item and provided 60 qualitative comments for item refinement and prioritisation.
Conclusion This Delphi study used a rigorous consensus process to reach consensus on 34 reporting items for studies that use mediation analysis. These results will inform a consensus meeting that will consolidate a core set of recommended items for reporting mediation analyses.
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Twitter @AidanCashin, @Pain_NeuRA, @hopinlee
Contributors AGC, HL and JHMcA conceived the idea for the project and prepared the initial list of reporting items. All authors contributed to the project design and protocol development. AGC and HL collected and analysed data with CLINVIVO. AGC wrote the first draft of the manuscript. All authors provided substantive feedback on the manuscript and have read and approved the final version.
Funding This work was supported by project funding from the Berkeley Initiative for Transparency in the Social Sciences, a programme of the Center for Effective Global Action (CEGA), with support from the Laura and John Arnold Foundation. The funding body did not contribute to the design of the study, the collection, analysis and interpretation of data and in writing the manuscript.
Competing interests AGC is supported by the University of New South Wales Prince of Wales Clinical School Postgraduate Research Scholarship and a NeuRA PhD Candidature Supplementary Scholarship, and is a Catalyst for the Berkeley Initiative for Transparency in the Social Sciences. HL is funded by the National Health and Medical Research Council (APP1126767); National Institute for Health Research (NIHR) Collaboration for Leadership in Applied Health Research and Care Oxford at Oxford Health NHS Foundation Trust; received project funding from the Berkeley Initiative for Transparency in the Social Sciences, a program of the Center for Effective Global Action (CEGA), with support from the Laura and John Arnold Foundation and is a Catalyst for the Berkeley Initiative for Transparency in the Social Sciences. SJK is funded by the National Health and Medical Research Council (APP1127932).
Patient consent for publication Not required.
Ethics approval Ethics approval was obtained from the University of New South Wales Human Research Ethics Advisory Panel D: Biomedical, approval number HC16599.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement The data set used and analysed during this study is available from the corresponding author on reasonable request.
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