Role of supplementary material in biomedical journal articles: surveys of authors, reviewers and readers.

OBJECTIVE: Many journals permit authors to submit supplementary material for publication alongside the article. We explore the value, use and role of this material in biomedical journal articles from the perspectives of authors, peer reviewers and readers. DESIGN AND SETTING: We conducted online surveys (November-December 2016) of corresponding authors and peer reviewers at 17 BMJ Publishing Group journals in a range of specialities. PARTICIPANTS: Participants were asked to respond to one of three surveys: as authors, peer reviewers or readers. RESULTS: We received 2872/20340 (14%) responses: authors 819/6892 (12%), peer reviewers 1142/6682 (17%) and readers 911/6766 (14%). Most authors submitted (711/819, 87%) and 80% (724/911) of readers reported reading supplementary material with their last article, while 95% (1086/1142) of reviewers reported seeing these materials sometimes. Additional data tables were the most common supplementary material reported (authors: 74%; reviewers: 89%; readers: 67%). A majority in each group indicated additional tables were most useful to readers (61%-77%); 20%-36% and 3%-4% indicated they were most useful to peer reviewers and journal editors, respectively. Checklists and reporting guidelines showed the opposite: higher proportions of each group regarded these as most useful to journal editors. All three groups favoured the publication of additional tables and figures on the journal's website (80%-83%), with <4% of each group responding that these do not need to be available. Approximately one-fifth (16%-23%) responded that raw study data should be available on the journal's website, while 24%-33% said that these materials should not be made available anywhere. CONCLUSIONS: Authors, peer reviewers and readers agree that supplementary materials are useful. Supplementary tables and figures were favoured over reporting checklists or raw data for reading but not for study replication. Journals should consider the roles, resource costs and strategic placement of supplementary materials to ensure optimal usage and minimise waste. TRIAL REGISTRATION NUMBER: NCT02961036.