Peer reviewers’ conflicts of interest in biomedical research: a scoping review of empirical studies

Session Type
Research integrity and fraud
Korfitsen CB1, Nejstgaard CH1, Hróbjartsson A1, Boutron I2, Bero L3, Lundh A1
1Cochrane Denmark & Centre for Evidence-Based Medicine Odense (CEBMO), Department of Clinical Research, University of Southern Denmark, Odense; Open Patient Data Explorative Network (OPEN), Odense University Hospital, Odense, Denmark
2Université de Paris, INSERM, INRAE, CNAM, Centre of Research in Epidemiology and Statistics (CRESS), F-75004 Paris, France
3Center for Bioethics and Humanities, University of Colorado Anschutz Medical Campus, Denver, Colorado, USA

Background: Peer review may improve the quality of submitted research manuscripts and assist in editorial decisions. While researchers’ and to some degree editors’ conflicts of interest have been thoroughly investigated, little is known about peer reviewers’ conflicts of interest.
Objectives: To systematically map and describe the extent and nature of empirical research on peer reviewers’ conflicts of interest in biomedical research.
Methods: Scoping review based on preregistered protocol ( We searched MEDLINE, Embase and The Cochrane Methodology Register (up to May 9, 2022) and other sources. We included studies investigating peer reviewers’ conflicts of interest in scientific manuscripts for biomedical journals, theses and dissertations, conference abstracts, funding applications, and clinical guidelines. Two authors independently included studies and extracted data on key study characteristics and results, and data were organised into emerging themes. We included studies explicitly aimed at investigating peer reviewers’ conflicts of interest in our primary analysis. Studies not aimed at this investigation, but reporting relevant results (e.g., studies of retractions reporting number of retractions due to peer reviewers’ conflicts of interest), were included in a sensitivity analysis.
Results: We included 69 studies and included 38 of these in our primary analysis. Sixteen (42%) of the 38 studies investigated peer reviewers’ conflicts of interest as their primary aim. The 38 studies were published between 2005 and 2021, and 27 (71%) investigated scientific manuscripts, one (3%) conference abstracts, four (11%) funding applications, and six (16%) clinical guidelines. Thirty-three (87%) studies were cross-sectional (14 of these used questionnaires), two (5%) qualitative interviews, and three (8%) mixed-methods. Nineteen (50%) studies investigated both financial and non-financial interests, six (16%) solely financial interests, four (11%) solely non-financial interests, and nine (24%) did not report it. The results of the thematic analysis and sensitivity analysis will be presented at the Colloquium.
Conclusions: We identified a considerable number of studies on peer reviewers’ conflicts of interest in biomedical research, primarily cross-sectional studies of peer review of scientific manuscripts. However, only a fourth of all identified studies investigated peer reviewers’ conflicts of interest as their primary aim. Further conclusions await our thematic analysis.