WoEshort forWeight of evidence - Weight of Evidence
A WOEshort forWeight of evidence approach is an internationally agreed upon procedure for the systematic, collective evaluation of and weighting of the results/data (lines of evidence) made available by various methods/approaches in order answer to research question.
This approach should be adopted if multiple independent sources of evidence are available. The WOEshort forWeight of evidence approach is intended to present the considerations that led to a particular set of conclusions in a trans- parent and comprehensible manner.
As regards the research question, this may involve a hypothesis (‘Is substance X carcinogenic?’) or be a problem concerning estimation (‘What proportion of the population is exposed to substance X at level Y?’). The term ‘evidence’ is understood to meanMeanTo glossary any relevant piece of information capable of answering the question. This may include data from scientific publications or a series of experiments that meet the minimum requirements for reliability and relevancePositive Predictive ValueTo glossary as defined in each case. WOEshort forWeight of evidence assessments made by the BfRshort forGerman Federal Institute for Risk Assessment are oriented on the EFSAshort forEuropean Food Safety Authority guidance document. The aim of the WOEshort forWeight of evidence assessment is to use the systematic collection, assessment and integration of available information in order to answer a specific scientific question on the basis of the entire body of knowledge available. During this process, the level of evidence, i. e. the formal and substantive quality of various potential answers, is explicitly reported.
The basic elements of a WOEshort forWeight of evidence assessment are the following three work steps:
- Consolidation
- Weighting, /critical evaluation
- Integration of evidence
In the first step, the scientific question is precisely defined. Key concepts and criteria are derived from this on the basis of which appropriate data sources are selected and researched. The overall aim here is to represent the existing body of knowledge as completely and faithfully as possible. Depending on the question at hand, a wide variety of information/data can be taken into account and assigned to ‘lines of evidence’ as required, such as in vivo, in vitro, in silico or epidemiological studies. Within a single line of evidence, there may be a variety of individual data sources (e.g. studies).
The second step concerns the weighing of evidence from the individual sources of information. The relevant criteria here include reliability (Are the results robust or is the set of data encumbered with significant constraints?), relevancePositive Predictive ValueTo glossary (Is the information relevant for answering the question and are the results transferable to the general conditions relevant for the question itself?) and consistency (Are the results comparable, reproducible and do they tend towards the same set of conclusions?). The criteria applied in each case must be presented clearly and comprehensibly. The evidence from the individual sources of information can be weighted qualitatively or quantitatively.
The third step involves integrating the insights from the individual sources of information while taking the weighting into account. Where possible, any distortion identified as affecting the body of knowledge (e.g. publication biasBiasTo glossary) should be accounted for. Integration is completed both at the level of the consolidation of insights within a line of evidence and also as part of a further step for the integration of different lines of evidence. The range of approaches for these integration steps once again comprises of qualitative and quantitative methods. The appropriate method in each case is selected in terms of scientific considerations, set standards (where available) and available processing time.