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Evidence-Based Nursing & PICO: Evidence-Based Practice

Levels of Evidence

Christopher Bauer, November 21, 2021 on Research Square.

Search for the highest quality evidence. Levels of evidence vary depending on how the evidence was gathered and tested. Clinicians use various hierarchies to rate quality of evidence. The highest level of evidence are listed first. Levels one through three constitute appraised or filtered levels, while levels four through eight are unfiltered. The chart in the box below this indicates where you should search for each level of evidence using Miami University databases. 

  1. Meta-Analysis  
  2. Systematic Reviews 
  3. Critically Appraised Sources
  4. Randomized Controlled Trials
  5. Cohort Studies
  6. Case Control Studies
  7. Case Reports/Case Series
  8. Background Information & Expert Opinion

These videos give additional information about levels of evidence and the evidence-based practice pyramid: 

Evidence-Based Practice, Step 2 (Part II) Searching - Levels of Evidence (by Molly Montgomery, Idaho State University, 5/26/2015, 4.53 min)

Evidence-Based Practice Pyramid & Levels of Evidence - Evidence-Practice for Librarians (by Molly Montgomery, Idaho State University, 7/13/2016, 8.05 min)

Where to Search for Evidence - Miami University Libraries

Levels of Evidence, Highest Listed First

Where to Search

  1. Meta-Analyses

  2. Systematic Reviews

  3. Critically Appraised Sources

  4. Randomized Controlled Trials

  5. Cohort Studies

  6. Case Control Studies

  7. Case Reports/Case series

  8. Background Information & Expert Opinion

Modified from Evidence-Based Practice Tools, Health Sciences Library, University of Washington, University Libraries

Evidence-Based Practice Tutorials and Guides

Three part webinar from the Network of the National Library of Medicine: Introduction to Evidence-Based Practice