• Evidence-Based Medicine
• Forward
  • Module Objectives
• Why Is EBM Important?
• Levels of Evidence
  • What Is Evidence?
  • Hierarchy of Evidence
  • Systematic Review
  • Systematic Review of Cohort Studies
  • Summary
• The EBM Process
  • Formulating a Clinical Question
    • Purpose of Clinical Question
    • Types of Clincal Questions
    • The Well-Built Questions: PICO
  • Searching for the Evidence
    • Cochrane
    • PubMed
    • Helpful Tips
  • Critically Appraise, Apply Evidence
• Resources
• Credits
• Return to Patient Safety & Quality Improvement

Levels of Evidence
Hierarchy of Evidence

The following are the levels of evidence, starting with the highest to lowest. This is not an absolute scale but is generally true. We will describe many but not all in this module.

1. Systematic reviews of RCTs (highest level of evidence)
   
2. Individual RCT (with narrow confidence interval)
   
3. Systematic review of cohort studies
   
4. Individual cohort study (and low quality RCT)
   
5. Outcomes research
   
6. SR (with homogeneity) of case-control studies
   
7. Individual Case-Control Study
   
8. Case series
   
9. Expert opinion (lowest level of evidence)
   • Centre for Evidence Based Medicine