There are many different approaches to rating evidence. See this handy comparison chart for some of the best-known rating systems. The tables below describe rating/grading guidelines frequently referenced at the Academy of Health Sciences.
|Evidence Rating||Evaluation Criteria|
|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|
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.
|Grade||Nomenclature||Definition for Research Evidence||Definition for Non-Research Evidence|
|A||High||Consistent results, sufficient sample size, adequate control, and definitive conclusions; consistent recommendations based on extensive literature review that includes thoughtful reference to scientific evidence||Expertise is clearly evident|
|B||Good||Reasonably consistent results, sufficient sample size, some control, and fairly definitive conclusions; reasonably consistent recommendations based on fairly comprehensive literature review that includes some reference to scientific evidence||Expertise appears to be credible|
|C||Low/Major Flaw||Little evidence with inconsistent results, insufficient sample size, conclusions cannot be drawn||Expertise is not discernable or is dubious|
From: Newhouse, Robin Purdy. Johns Hopkins Nursing Evidence-Based Practice Model and Guidelines, p. 207.
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