Nursing: Evidence-Based Practice: Evidence Levels, Recommendations & Types

1. Ask a clear clinical question

2. Acquire best available evidence

3. Appraise evidence for quality

4. Apply evidence to practice

5. Assess the outcomes

When you start researching you will encounter many different types of evidence such as systematic reviews, randomized controlled trials, clinical guidelines and opinion articles.  These different resources will not all have the same "weight" in terms of reliability and trustworthiness.  To assist you in determining what is the most reliable, the levels of evidence hierarchies will guide you.

Evidence Hierarchies are systems used to rank evidence according to certain criteria.  There are many hierarchies, including the examples on this page.

Source:

Hopp, L., & Rittenmeyer, L. (2012). Introduction to evidence-based practice: A practical guide for nursing. Philadelphia: F.A. Davis.

These resources provide additional information on the levels of evidence.

View grades of recommendations at the following links:

JBI Grades of Recommendation

This evidence pyramid provides a concept of higher to lower levels of evidence.

Source:  UIC Evidence Based Practice Tutorial, ebp.lib.uic.edu

The Joanna Briggs Institute adopted a new hierarchy for levels of evidence as of March 1, 2014.  The chart below outlines the levels of evidence for effectiveness questions.

The Joanna Briggs website contains levels of evidence charts for other types of questions.

Definitons of research designs from Introduction to Evidence Based Practice:  A Practical Guide for Nursing by Lisa Hopp and Leslie Rittenmeyer.

Case Controlled studies are where researchers conduct a comparison of cases with a particular outcome and cases without a particular outcome to evaluate the participants’ exposure. 

Case Series/Case Report is a research design that track patients with a known exposure given similar treatment or examines their medical records for exposure and outcome.  

Cohort studies with a control group are those where a group of people with something in common (a cohort) are followed.  This group is compared to another group with similar characteristics/circumstances, with the exception of the factor being investigated.

Cross-sectional studies involve data collected at a defined time, providing a snapshot of a disease in the population (observational studies).

Meta-analysis uses statistical methods to pool the results of independent studies (quantitative).  Meta-synthesis is a qualitative analysis of a group of individual studies in which the finding of the studies are pooled.

Randomized Clinical Trial is an experiment using human beings in which the investigator randomly assigns participants in the trial either to a treatment or control (no treatment) group.

Systematic Reviews attempt to synthesize and summarize evidence from existing primary studies. They use explicit and transparent methods to include/exclude studies on a topic, and rigorously analyze the results to form a conclusion.