Weight of Evidence for Hazard Identification: A Critical Review of the Literature

BACKGROUND: Transparency when documenting and assessing weight of evidence (WOE) has been an area of increasing focus for national and inter-national health agencies.
OBJECTIVE: The objective of this work was to conduct a critical review of WOE analysis methods as a basis for developing a practical framework for considering and assessing WOE in hazard identification in areas of application at the French Agency for Food, Environmental and Occupational Health and Safety(ANSES).
METHODS: Based on a review of the literature and directed requests to 63 international and national agencies, 116 relevant articles and guidance documents were selected. The WOE approaches were assessed based on three aspects: the extent of their prescriptive nature, their purpose-specific relevance, and their ease of implementation.
RESULTS: Twenty-four approaches meeting the specified criteria were identified from selected reviewed documents. Most approaches satisfied one or two of the assessed considerations, but not all three. The approaches were grouped within a practical framework comprising the following four stages: (1) planning the assessment, including scoping, formulating the question, and developing the assessment method; (2) establishing lines of evidence (LOEs), including identifying and selecting studies, assessing their quality, and integrating with studies o fsimilar type; (3) integrating the LOEs to evaluate WOE; and (4) presenting conclusions.
DISCUSSION: Based on the review, considerations for selecting methods for a wide range of applications are proposed. Priority areas for further development are identified.