Evidence Synthesis (Systematic Reviews)

See "Guidance for Evidence Synthesis" for official guidelines from national and international evidence synthesis organizations

1. Assemble a Team 

• At least three people to reduce bias in screening, quality analysis, and data extraction
• Subject experts 
• Librarians
• Experts who can advise on quality assessment tools for different study types
• Statisticians (especially if you are conducting a meta-analysis)

2. Develop a Research Question

• See Developing the Research Question for some common frameworks (such as PICO) 
• The research question will help you choose the right review type.  

3. Define Inclusion and Exclusion Criteria

• Examples of common Inclusion criteria:
  • Characteristics of the population
  • Specific interventions or concepts 
  • study types (i.e. qualitative, quantitative, both)
  • Date parameters
  • Language
• Examples of common exclusion criteria:
  • Certain publication types like editorials, news items, or books
  • Items in languages that the team cannot easily translate
  • Studies that don't reflect the target populations, interventions, or concepts
  • Animal or cadaver studies

4. Write and Register a Protocol 

• See Writing and Registering a Protocol

4. Search the Literature

• Search at least three bibliographic databases
• Use controlled vocabulary and keywords 
• More details are provided in Literature Search tab

5.  Screen and Select Studies for analysis

• Usually conducted in two passes
  • Review title and abstract
  • Review full text
• Covidence software can help with this step!

6. Assess study quality (may not be appropriate for all review types)

• Each study meeting the inclusion criteria is assessed for quality
• Use a quality assessment tool that matches the type of studies you are analyzing. 

7. Extract Data

• Reviewers will extract information from the included documents to be analyzed either qualitatively or quantitatively.

8. Analyze and Present Results

• Can be qualitative, quantitative or both

9. Interpret Results

Reviewers should comment on:

• Strength of the evidence
• Applicability of the results
• Benefits/costs/tradeoffs
• Limitations
• Implication for future research

10. Update the Review as Needed

• New research findings can quickly make Evidence Synthesis reviews out of date.