EvSyS: The Evidence Synthesis Selection Tool for Decision Makers

As a decision-maker, have you ever wondered which type of evidence synthesis is best for your purpose? Or do you need to have a review of evidence completed?

This tool will help you determine which type of synthesis is right for you. 

Research is being conducted all the time in public health! It is impossible to keep up-to-date with every study published. This is why evidence syntheses are helpful.



Evidence syntheses summarize evidence on a particular topic in a specific way. Evidence at this level reflects what is known about the topic or question and is more relevant for decision making.



Just as there are many types of research, there are also many ways to summarize evidence. Each approach is appropriate for different scenarios and purposes. The approach you use depends on factors such as the time you have or the available evidence.


Decision-makers may be unsure whether a scoping review or systematic review is best, or whether other variations such as a rapid review or living review may be necessary. This tool was designed for public health decision-makers working with evidence synthesis teams to conduct or commission an evidence synthesis. This tool will help you understand which evidence synthesis approach is best for you.


Take note:

Although these are the most common types of evidence syntheses, they may not be appropriate for all types of evidence. New evidence synthesis methodology is emerging all the time. This tool is not meant to be a comprehensive review of all available synthesis methods. Instead, it is a starting point for decision-makers to identify the most appropriate type of evidence synthesis to meet their needs and context.

If you are a researcher looking to identify the correct type of review to conduct, consider using the Right Review tool.

For additional support, visit our Registry of Methods and Tools to find other tools for various types of evidence. Visit our Learning Centre for more information on review types. Sign up for our monthly newsletter to stay up-to-date on new products.



Is a new evidence synthesis really needed at this time?

Conducting or commissioning an evidence synthesis can be a resource-intensive activity.

To reduce duplication of efforts, we strongly recommend conducting a preliminary search and only proceeding if no relevant, recent and rigorous reviews are available.

  • Relevant: The review adequately answers your question. Think about population, intervention or exposures, outcomes and context.
  • Recent: Cochrane recommends that systematic reviews be revisited every two years, but this will depend on how quickly new evidence on the topic is published.
  • Rigorous: This means there is a low risk of bias when appraised using AMSTAR or another appropriate critical appraisal tool.


Key resources for preliminary searching:

  • Health Evidence – a database of pre-appraised systematic reviews of public health interventions.
  • McMaster Health Forum’s Evidence Products – a database of rapid syntheses, evidence briefs and citizen briefs that combine research evidence with stakeholder and citizen input.
  • NCCMT’s Rapid Evidence Service – a service that answers priority questions from public health professionals with rapid reviews related to COVID-19 and beyond.
  • 6S Search Pyramid Tool – A guide for finding the best available research evidence quickly and efficiently. Each level of the pyramid draws on research evidence from the lower layers, therefore more synthesized evidence is found at the higher levels. 
  • Public Health + – a database of only high-quality pre-appraised studies and reviews relevant to public health
  • The Community Guide – a resource to help you select interventions to improve health and prevent disease in your region, community, community organization, business, healthcare organization or school.