What are Levels of Evidence?
- In evidence-based practice, individual research studies are ranked and assigned levels of evidence based on their methodological rigor and strength
- Study designs with the least potential risk for bias are at the top of the evidence hierarchy
- Study designs with greater risk for bias are ranked lower
- There are several variations of evidence hierarchy models. In most of these hierarchies, systematic reviews of randomized controlled trials are ranked highest, with expert opinion ranked lowest.
- Evidence levels are primarily an indicator of potential risk for bias being present in the study results, with the least risk for bias at the top and higher risk for bias at the bottom
References
Guyatt G. Rennie D. Meade M. Cook D. & American Medical Association. (2015). Users' guides to the medical literature: A manual for evidence-based clinical practice (3rd ed.). McGraw-Hill Education.
