There are several renditions of levels and pyramids that describe or illustrate respectively the levels of evidence of research. In Lynn Kysh's pyramid below (from What's In a Name?: The Difference Between a Systematic Review and a Literature Review and Why It Matters) we see a four level breakdown.
- Lynn Kysh, Librarian, USC Norris Medical Library
In the Johns Hopkins Nursing EBP, there are five levels listed and described. In essentials they are the same. The Johns Hopkins version, like many other versions, break down the categories in a more granular fashion. In all versions, however, systematic reviews are at the top of the pyramid and case reports appear at the bottom in evidence value.
Experimental study, randomized controlled trial (RCT)
Systematic review of RCTs, with or without meta-analysis
Systematic review of a combination of RCTs and quasi-experimental, or quasi-experimental studies only, with or without meta-analysis.
Systematic review of a combination of RCTs, quasi-experimental and non-experimental, or non-experimental studies only, with or without meta-analysis.
Qualitative study or systematic review, with or without meta-analysis
Opinion of respected authorities and/or nationally recognized expert committees/consensus panels based on scientific evidence.
- Clinical practice guidelines
- Consensus panels
Based on experiential and non-research evidence.
- Literature reviews
- Quality improvement, program or financial evaluation
- Case reports
- Opinion of nationally recognized expert(s) based on experiential evidence
Dang, D., & Dearholt, S.L. (2018). Johns Hopkins nursing evidence-based practice : Model & guidelines (3rd ed). Sigma Theta Tau International.
A final example is an EBM Pyramid from Dartmouth and Yale which also labels filtered and unfiltered evidence on the scale.