What is Evidence Synthesis?

Evidence synthesis is the interpretation of individual studies within the context of global knowledge for a given topic. These syntheses provide a rigorous and transparent knowledge base for translating research in decisions. As such, evidence syntheses can be thought of as the basic unit of knowledge used in tools such a policy brief or clinical practice guideline. In other words, evidence syntheses are the “evidence-base” in evidence-based policy, or evidence-based medicine etc. Essential to all evidence syntheses is the use of explicit and transparent methodology in the formation of the questions they address. The transparent methodology encompasses how studies are identified, selected, appraised, analyzed, and the strength of the evidence assessed to answer the questioned posed.

The advantage of evidence synthesis methods is that all studies on a topic are assessed together in context. Individual studies may make headlines but until they are put in context of what is already known they should not form the basis of decision making. It is easy to find studies or ‘experts’ that contradict one another which is why pooling all available evidence through a transparent method is essential.

Evidence syntheses methods have been applied to a diverse and growing number of areas. Applications, include: education, crime and justice, international development, health care delivery, health technology assessment, veterinary medicine, pre-clinical drug development and toxicology, food safety, and environmental conservation. As equally diverse as the applications are the organizations that conduct, commission, and utilize the evidence synthesis.