Step 2:Locating the

Evidence

Table of Contents• Evidence Pyramid

– Filtered Information•Systematic Reviews/Meta-Analyses•Critically-Appraised Topics (Synthes

is)•Critically-Appraised Articles (Synop

sis)

– Unfiltered Information•Randomized Controlled Trials•Cohort Studies•Case-Controlled Studies/ Case Serie

s and Reports•Background Info/ Expert Opinion

Evidence Pyramid

• The best evidence is located at the top of the pyramid.

• Click on one of the sources of evidence to learn more.

Filtered Information

• Appraise and/or synthesize information from previous studies

• Organize it into a single coherent analysis

• Provide recommendations for future practice.

Systematic Reviews/ Meta-

Analyses• Systematic reviewsSystematic reviews

– Comprehensively synthesize and critically appraise information from various articles that meet specific selection criteria

– Provide recommendations based on the best evidence available

Systematic Reviews/ Meta-

Analyses• Meta-analysesMeta-analyses

– Are systematic reviews using statistical methods to quantitatively combine and summarize several studies’ results

Critically-Appraised

Topics (Synthesis)• Briefly evaluate and

synthesize results from several studies on a particular topic that provide the best available evidence relevant to answering a specific clinical question

• Less rigorous than systematic reviews/meta-analyses

Critically-Appraised

Articles (Synopsis)

• Provide a brief synopsis and appraisal of a single study that provides evidence relevant to answering a specific clinical question

• Less rigorous than systematic reviews/meta-analyses

Unfiltered Information

• The evidence sources from which the above ones acquire their information (i.e. the primary sources)

• Useful when filtered information is not available

Randomized Controlled

Trials• Randomly assigns

subjects into a treatment group or a control group in order to compare the efficacy of a particular treatment, diagnosis, etc. against the current standard, a placebo, or no intervention at all.

Cohort Studies

• Compare two groups of subjects over time, one having a particular condition or receiving a particular treatment, the other not

• Often used when a randomized controlled trial would be unreasonable or unethical.

Case-Controlled Studies/ Case

Series and Reports

• Retrospective observational studies of a particular diagnosis or exposure

• Determine commonalities in medical history or other associations amongst the affected

• Can establish correlations, but cannot prove causation

Background Info/ Expert

Opinion• Based on clinical

experience and case studies

• Varies in level of scientific rigor and usefulness.

Try it Yourself:

• Search Basics & Using PubMed

• More Advanced Searches & Using the Cochrane Library

Additional Resources forSystematic Reviews\ Meta-

AnalysesOnline Resources:• PubMed• Cochrane LibrarySelected Readings:• Systematic Reviews: Synthesis

of Best Evidence for Clinical Decisions by Cook, D. J., et al.

Links to Other Websitesand Hands-On Activities

• From Duke University Medical Center Library and Health Sciences Library, UNC-Chapel Hill – Types of Studies

• From Yale University School of Medicine– Evidence Pyramid from a Slightly

Different Perspective

Congratulations!

You have successfully completed Step 2 – Evidence Pyramid.

The End