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Hierarchy of Evidence

The "best available evidence" in the hierarchy of evidence refers to:

Systematic Reviews and Meta-Analyses

Well-conducted systematic reviews and meta-analyses are generally considered to provide the highest level of evidence for all types of questions in evidence-based practice (EBP) hierarchies. This is because:

• Systematic reviews synthesize the results from all available studies on a particular topic through comprehensive literature searches and thorough analysis.
• Meta-analyses combine and analyze the data from multiple studies, providing a more reliable summary of evidence than individual studies.
• The greater the number and diversity of participants and settings included in a meta-analysis, the more convincing the evidence.

However, it is important to note that the position of systematic reviews at the top of the evidence hierarchy is not absolute. If a current, well-designed systematic review is not available, one should move down to the next level of evidence, which typically consists of primary studies such as randomized controlled trials (RCTs), cohort studies, or case-control studies, depending on the type of question being addressed. Additionally, the quality of a systematic review depends on the quality of the studies included, and a large, well-conducted RCT may provide stronger evidence than a systematic review of small or poor-quality studies. In summary, while systematic reviews and meta-analyses are generally considered the "best available evidence" in EBP hierarchies, the specific study design that provides the highest level of evidence may vary depending on the availability of high-quality systematic reviews and the type of question being addressed.

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