Answered By: Nicole Montgomery
Last Updated: Oct 17, 2018     Views: 32

Levels of evidence (sometimes called hierarchy of evidence) Pyramid presentation of the evidence levels presented in text on this FAQare assigned to studies based on the methodological quality of their design, validity, and applicability to patient care. These decisions gives the "grade (or strength) of recommendation."

Level I
Experimental study, randomized controlled trial (RCT)
Systematic review of RCTs, with or without meta-analysis

Level II
Quasi-experimental Study
Systematic review of a combination of RCTs and quasi-experimental, or quasi-experimental studies only, with or without meta-analysis.

Level III
Non-experimental study
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

Level IV
Opinion of respected authorities and/or nationally recognized expert committees/consensus panels based on scientific evidence.

  • Clinical practice guidelines
  • Consensus panels

Level V
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


The above information is also reflected in the below table.:


Level of Evidence (LOE) Description
Level I Evidence from a systematic review or meta-analysis of all relevant RCTs (randomized controlled trial) or evidence-based clinical practice guidelines based on systematic reviews of RCTs or three or more RCTs of good quality that have similar results.
Level II Evidence obtained from at least one well-designed RCT (e.g. large multi-site RCT).
Level III Evidence obtained from well-designed controlled trials without randomization (i.e. quasi-experimental).
Level IV Evidence from well-designed case-control or cohort studies.
Level V Evidence from systematic reviews of descriptive and qualitative studies (meta-synthesis).
Level VI

Evidence from a single descriptive or qualitative study.

Level VII Evidence from the opinion of authorities and/or reports of expert committees.



Adapted from Evidence Based Practice Toolkit for Nursing by the OHSU Library who used Johns Hopkins nursing evidence-based practice : Models and Guidelines
Dearholt, S., Dang, Deborah, & Sigma Theta Tau International. (2012). Johns Hopkins Nursing Evidence-based Practice : Models and Guidelines.

Adapted from Evidence Based Toolkit from Winona State University Library who used Ackley, B. J., Swan, B. A., Ladwig, G., & Tucker, S. (2008). Evidence-based nursing care guidelines: Medical-surgical interventions. (p. 7)St. Louis, MO: Mosby Elsevier.