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WRI 1100: Aaberg


PICO is a framework for asking focused clinical questions.

PICO stands for:

Patient and Problem

Intervention or exposure

Comparison or Control


Evidence Based Practice Hierarchy

Evidence Based Practice PyramidHierarchy of Evidence Summary

Level I: a. Evidence of a systematic review or meta analysis of all relevant randomized controlled trials (RCT), or evidence-based clinical practice guidelines based on the above.
​b. Evidence of a systematic review of RCTs
​c. Evidence of a systematic review of nonrandomized trials

Level II: a. Evidence from at least 1 RCT.
​b. Single nonrandomized trial

Level III: Evidence from a systematic review of correlational/observational studies

Level IV: Evidence from a single correlational/observational study

Level V: Evidence from systematic reviews of descriptive,  qualitative or physiologic studies.

Level VI: Evidence from a single descriptive, qualitative, or physiologic study.

Level VII: Evidence of authority opinion or reports of expert committees.

Pyramid modified from: Navigating the Maze, University of Virginia, Health Sciences Library, by University of Washington. Health Sciences Library and Information Center

Evidence Based Practice Resources

Cochrane Database of Systematic Reviews:

Other Systematic Reviews and Meta-Analyses:

Evidence Guidelines

RCTs, Case Cohorts, Control Studies

Clinical Research Critiques

Other Reviews of the Literature

Case Reports, Case Series, Other Articles, Practice Guidelines

Clinical Reference Texts:

Meta-Search Tools:

  • TRIP+ Database (Turning Research Into Practice) - this database arranges results using the hierarchy of evidence levels.
  • SUMSearch- University of Kansas, returns research broken down into original research, systematic reviews, and guidelines
  • Epistemonikos - Metasearch in mutilple languages

Resources for Critiquing the Quality of your Sources:

Basic Information and Tutorials about EBP: