Evidence-Based Research: Levels of Evidence Pyramid

Levels of evidence pyramid

Evidence-based practice

As you move from the base of the pyramid, the quality of evidence increases, with systematic reviews being the highest quality. As you move from the top of the pyramid, the amount of available evidence increases, with expert opinion and background information being the most plentiful and common.

Systematic Reviews/Meta-Analysis

Critically-appraised topics (Evidence Syntheses)

Critically-appraised article (Article Synopses)

Randomized Controlled Trials (RCTs)

Cohort Studies

Case-Control/Case-Comparison Studies; Case Studies/Reports

Expert Opinion/Background Information

Unfiltered Information

Unfiltered information refers to original research studies that have not yet gone through synthesis. They are not immediately ready to apply to practice, and will require interpretation. These are primary sources. You can find these types of evidence in CINAHL and MEDLINE.

Randomized Controlled Trial

A randomized controlled trial or RCT is an experimental research design where participants are randomly assigned to different groups. This method allows researchers to assess the effectiveness of an intervention or treatment by reducing the potential for bias. There will be an intervention group and a control group. Click the link at the top left to view the full example article.

Cohort Studies

A cohort study is a longitudinal observational research design that follows a group of individuals (cohort) over time to examine the development of specific outcomes. It does not involve intervention implemented by the researchers, and is observational. Researchers might hypothesize that exposure to certain factors might influence participants in the cohort towards certain outcomes. Click the link at the top left to view the full example article.

Critically-Appraised Topic

A critically-appraised topic (CAT) is a short summary of the best available evidence, created to answer a specific clinical question. Authors of CATs evaluated and synthesize mutiple research studies. Click the link at the top left to view the full example article.

Critically-Appraised Article

A critically-appraised article is an evaluation of a single research study, where the authors discuss methodology and generalizability of results. This is not the same thing as peer-review. A peer-reviewed article still needs to be critically appraised. Click the link at the top left to view the full article on steps in critically appraising a research study or article.

Filtered Information

Information that has been filtered has gone through a critical appraisal and can be used for clinical decision-making at the point-of-care. These are secondary sources. Use CF's Cochrane Library database to find systematic reviews. You can also use the systematic review filter in CINAHL.

Systematic Reviews/Meta-Analysis

Authors of systematic reviews pose a clinical question, conduct a comprehensive review of the available literature, and exclude studies that do not meet their criteria. The goal is to make recommendations for clinical practice based on well-conducted studies. A meta-analysis is a kind of systematic review that uses quantitative methods for its summary. Click the link at the top left to view the full example article of a systematic review.

Case Studies

This section of the Evidence Pyramid includes: Case-control studies which compares individuals with a particular condition (case) to those without it (control); Case study/series which is an in-depth analysis of a group of patients with a similar diagnosis or condition, or a particular individual, without a control group for comparison. Click the link at the top left to view the full example article of a case study.

Expert Opinion/Editorial

Expert opinion or editorial information on a subject can appear as a journal article, like our example. You can also find foundational information in a handbook, encyclopedia (including websites), and textbooks. The information within these sources is generalized and can take the longest to be published. It is also the most widely available and lowest level of evidence possible. Click the link at the top left to view the full example article.