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Evidence Based Practice for Nursing Tutorial

Levels of Evidence

The quality of evidence pyramid with Background information on the bottom, then case controlled studies, then cohort studies, then RCTs, then critically appraised articles, then systematic reviews.Levels of evidence are used to evaluate and rank the authority of particular research methods. While higher levels of evidence are more rigorous with less risk of bias, it is important to consider that some studies are more appropriate for answering particular research questions. The evidence hierarchy is meant as a decision tool to be combined with clinical judgement. 

 

Levels of evidence are often illustrated as a pyramid, with the highest levels at the top (as seen here). However, there are a variety of rating systems available, including but not limited to the Melnyk model and the Hopkins model. 

 

 

Image: EBM Pyramid and EBM Page Generator, copyright 2006 Trustees of Dartmouth College and Yale University. All Rights Reserved. Produced by Jan Glover, David Izzo, Karen Odato and Lei Wang.

Melnyk Model
LEVEL OF EVIDENCE STUDY DESIGN
Level I Systematic reviews and meta-analysis of randomized controlled trial
Level II Randomized controlled trial
Level III Non-randomized controlled trial (quasi-experiment)
Level IV Case-control or cohort studies
Level V Systematic reviews of qualitative or descriptive studies
Level VI Qualitative or descriptive studies
Level VII Opinion of authorities and/or reports of expert committees

Adapted from Melnyk, B.M. & Fineout-Overholt, E. (2015). "Box 1.3: Rating system for the hierarchy of evidence for intervention/treatment questions" in Evidence-based practice in nursing & healthcare: A guide to best practice (3rd ed.) (pp. 11). Philadelphia, PA: Wolters Kluwer Health.

John Hopkins Evidence-Based Practice Model (JHEBP)

 

The JHEBM uses a five-level evidence rating system to appraise evidence, and includes research (Levels 1, 2, and 3) and non research (Levels 4 and 5) evidence. For more information, consult Johns Hopkins evidence-based practice for nurses and healthcare professionals : model and guidelines.

Dang, D., Dearholt, S., Bissett, K., Ascenzi, J., & Whalen, M. (2022). Johns Hopkins evidence-based practice for nurses and healthcare professionals: model and guidelines. 4th ed. Indianapolis, IN: Sigma Theta Tau International

 

EVIDENCE LEVEL TYPES OF EVIDENCE
Level I
  • Experimental study, randomized control trial (RCT)
  • Explanatory mixed methods design that includes only a Level I quantitative study
  • Systematic review of RCTs, with or without meta-analysis
Level II
  • Quasi-experimental study
  • Explanatory mixed methods design that includes only a Level II quantitative study
  • Systematic review of a combination of RCTs and quasi-experimental studies, 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 nonexperimental studies, or non experimental studies only, with or without meta-analysis
  • Exploratory, convergent, or multiphase mixed methods studies
  • Qualitative study
  • Systematic review of qualitative studies, with or without meta-synthesis
Level IV

Opinions of respected authorities and/or nationally recognized expert committees or consensus panels based on scientific evidence. Includes:

  • Clinical practice guidelines
  • Consensus panels/position statements
Level V

Based on experiential and non-research evidence. Includes: 

  • Scoping reviews
  • Integrative reviews
  • Literature reviews
  • Quality improvement, program or financial evaluation
  • Case reports
  • Opinion of nationally recognized expert(s) based on experiential evidence

Adapted from Hierarchy of Evidence Guide, Appendix D, Johns Hopkins Evidence-Based Practice Model for Nursing and Healthcare Professionals. © 2022 Johns Hopkins Health System/Johns Hopkins School of Nursing.

© 2022 Johns Hopkins Health System/Johns Hopkins School of Nursing.

Study Design

 

WHICH TYPE OF EVIDENCE BEST ANSWERS YOUR CLINICAL QUESTION?

QUESTION TYPES OF EVIDENCE
All clinical questions Systematic review, Meta-analysis
Treatment/Therapy Randomized controlled trial (Also: Meta-analysis, Cohort study, Case-control study)
Etiology Cohort study (Also: RCT, Meta-analysis, Case-control study, Case series)
Diagnosis RCT &/or Cohort study (Also: Cross-sectional study)
Prognosis Cohort Study &/or Case-control study (Also: Case series) 
Prevention Prospective study &/or RCT (Also: Cohort study, Case-control study, Case series)
Meaning Qualitative study

Adapted from Finest-Overholt, E. & Johnston, L. (2005). "Table 3 Examples of different types of clinical questions using PICOT format and types of evidence to answer the given question" in Teaching EBP: Asking searchable, answerable clinical questions. Worldviews on Evidence-Based Nursing. Copyright © 2005 Sigma Theta Tau International