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Evidence-Based Practice Research: Levels of Evidence Pyramid

Introduction

One way to organize the different types of evidence involved in evidence-based practice research is the levels of evidence pyramid.

On this page you will find an image of the evidence pyramid as well as links to databases, websites, and journals where you can find:

  • Filtered resources
    • systematic reviews
    • critically-appraised topics
    • critically-appraised individual articles
  • Unfiltered resources
    • randomized controlled trials
    • cohort studies
    • case-controlled studies, case series, and case reports
  • Background information, expert opinion

Levels of evidence pyramid

The levels of evidence pyramid provides a way to visualize both the quality of evidence and the amount of evidence available. For example, systematic reviews are at the top of the pyramid, meaning they are both the highest level of evidence and the least common. As you go down the pyramid, the amount of evidence will increase as the quality of the evidence decreases.

EBM Pyramid and EBM Page Generator, copyright 2006 Trustees of Dartmouth College and Yale University. All Rights Reserved.
Produced by Jan Glover, David Izzo, Karen Odato and Lei Wang.

Filtered Resources

Filtered resources appraise the quality of studies and often make recommendations for practice. The main types of filtered resources in evidence-based practice are:

 

Below you will find links to resources where you can find each of these types of filtered information.

Systematic reviews

Authors of a systematic review ask a specific clinical question, perform a comprehensive literature review, eliminate the poorly done studies, and attempt to make practice recommendations based on the well-done studies. Systematic reviews include only experimental, or quantitative, studies, and often include only randomized controlled trials.

You can find systematic reviews in these filtered databases:

 

You can also find systematic reviews in this unfiltered databases:

 

To learn more about finding systematic reviews, please see our guide:

Critically-appraised topics

Authors of critically-appraised topics evaluate and synthesize multiple research studies. Critically-appraised topics are like short systematic reviews focused on a particular topic.

You can find critically-appraised topics in these resources:

 

To learn more about finding critically-appraised topics, please see our guide:

Critically-appraised individual articles

Authors of critically-appraised individual articles evaluate and synopsize individual research studies.

You can find critically-appraised individual articles in these resources:

 

To learn more about finding critically-appraised individual articles, please see our guide:

Unfiltered resources

You may not always be able to find information on your topic in the filtered literature. When this happens, you'll need to search the primary or unfiltered literature. Keep in mind that with unfiltered resources, you take on the role of reviewing what you find to make sure it is valid and reliable.

Note: You can also find systematic reviews and other filtered resources in these unfiltered databases.

Here are some unfiltered databases where you can find randomized control trials, cohort studies, case-controlled studies, case series, and case reports:

 

To learn more about searching unfiltered resources for certain types of studies, please see our guide:

Background information & expert opinion

Background information and expert opinions are not necessarily backed by research studies. They include point-of-care resources, textbooks, conference proceedings, etc.

TRIP database

You may hear about a resource called the TRIP database. This is a clinical, evidence-based research search engine anyone can access on the Internet.

The TRIP database searches both filtered and unfiltered resources. It can sometimes link you into full text content, but there is no full text available within TRIP itself.

Because it can be difficult to get to the full text, TRIP is not recommended for assignments related to finding specific types of evidence-based research. It also may not have many results for a specific evidence level on every topic.

You may want to explore and familiarize yourself with this online search engine even if you use our databases for your scholarly research. It is important to know about TRIP since it is an invaluable online search engine for practitioners and clinicians, particularly if they do not have access to the same databases we provide in the Walden Library.