In this guide you will find Evidence-Based Practice tools, as well as recommended databases, books, practice sites, and information about Evidence-Based Research. Evidence-Based Medicine (EBM) is the integration of clinical expertise, patient values and the best research evidence into the decision making process for patient care.
Clinical expertise refers to the clinician’s cumulated experience, education and clinical skills. The patient brings to the encounter his or her own personal preferences and unique concerns, expectations, and values. The best research evidence is usually found in clinically relevant research that has been conducted using sound methodology. (Sackett D, 2002)
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.
Filtered Information (secondary literature)
Systematic Review - Uses explicit rigorous methods to identify, critically apprise, and synthesize relevant studies
Meta Analysis - A quantitative method of combining the results of independent studies and synthesizing summaries and conclusions that may be used to evaluate therapeutic evidence
Critically Apprised Topic (CAT's) - A summary of the best evidence on a topic. CAT's usually include evidence from more than one study, are brief and their methods are less rigorous than SR
Critically Appraised Individual Article - A summary of a single paper, authors evaluate and synopsize individual research study
Unfiltered Information (primary literature)
Randomized Controlled Trial - A clinical trial that subjects are assigned randomly to one of two groups with one group is receiving intervention and is tested and the other is receiving alternative treatment and the follow up
Cohort Study - An observational study that compares two groups with exposure of interest and control one (no exposure)
Case Control Trial - A study that identifying subjects with disease of interest and control group without the disease and comparison
Clinical Trial - Pre-planned studies to answer questions on safety or efficacy of specific interventions according to protocol or research plan created by investigators
Studies are assigned levels of evidence based on their methodology. The evidence pyramid is an easy way to visualize this hierarchy of evidence.
At the top of the pyramid is filtered evidence including systematic reviews, meta-analyses, and critical appraisals. These studies evaluate and synthesize the literature. The top of the pyramid represents the strongest evidence.
At the base of the pyramid is unfiltered evidence including randomized controlled trials, cohort studies and case reports. These are individual reports and studies, also known as the primary literature.
You should seek the highest level of evidence available, but remember that evidence at the top of the pyramid might not exist for your particular clinical question. If that is the case, you'll need to move down the pyramid to find the strongest evidence that addresses your clinical question.
Evidence Rating |
Evaluation Criteria |
Level I
|
Evidence from a Systematic Review or Meta-Analysis of all relevant Randomized Controlled Trials (RCTs) or evidence based Clinical Practice Guidelines based on systematic reviews of RCTs |
Level II |
Evidence obtained from at least one well-designed RCT |
Level III |
Evidence obtained from well-designed Controlled Trials without Randomization |
Level IV |
Evidence from well-designed Case-Control and Cohort Studies |
Level V |
Evidence from Systematic Reviews of descriptive and qualitative studies |
Level VI |
Evidence from a single descriptive or qualitative study |
Level VII |
Evidence from the opinion of authorities and /or reports of expert committees |
From: Melnyk, Bernadette Mazurek, and Ellen Fineout-Overholt. Evidence-Based Practice in Nursing & Healthcare: A Guide to Best Practice
Image source: Georgetown University Medical Centre