Perspectives on the definition of 'evidence': a qualitative interview study among interest-holders

To clarify the perspectives of different interest-holders on the definition of 'evidence'.

This qualitative study employed purposeful sampling to select respondents from various disciplines and fields worldwide for semistructured interviews. The initial draft of the interview guide was developed based on a scoping review of definitions of 'evidence' and relevant documents. A pilot test was conducted to refine the interview guide. Interviews were conducted both online and in person until data saturation was achieved. Interview transcripts were analysed in NVivo V.12 using thematic analysis, which involved generating initial codes, searching for and reviewing themes and agreeing on the final set of themes.

Interviews were conducted with 25 interest-holders from 16 countries, including policymakers, researchers, journal editors, clinicians and representatives of patients and the public. Findings show that most respondents believe there is a lack of clear, precise definitions of evidence and that the term is used variably and informally. Although respondents identified multiple barriers to establishing a standardised definition, some questioned whether a new definition is necessary, argued that existing definitions are sufficient or noted the practical difficulties of developing one. Moreover, views differed on which interest-holders should be involved and considered in developing such a definition. Based on these discussions, 13 of the 25 respondents explicitly provided personal definitions of 'evidence' for users' reference.

The unclear definitions of evidence and their inconsistent usage not only lead researchers to misunderstand and overuse the term but also contribute to the misuse or mistrust of evidence by users, especially patients and the public, and even to criticism of evidence-based practice. We urge users to consult existing definitions of the term 'evidence' before employing it, to ensure standardised and accurate usage. If no accepted definition is available, we recommend clearly defining the term prior to use, so that users can accurately comprehend its meaning.