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Nursing

Levels of Evidence Hierarchy

For clinical questions, articles with the highest quality of evidence are best. The pyramid represents the Levels of Evidence Hierarchy. Studies are assigned to a level based on their design and strength of recommendation.

                                          

                            Source: Wood, G. L, & Haber, J. (2014). Nursing research: Methods and critical appraisal of evidence-based practice (8ed). St. Louis: Mosby/Elsevier

Types of studies

Level I

  • Clinical Practice Guideline: Recommendations for clinicians based on a systematic review of evidence.
  • Meta-Analysis: Combines the results of studies using quantitative methods to statistically estimate the effects of proposed interventions.
  • Systematic Review: Appraised summary of all experimental or quantitative research addressing a specific clinical question.

Level II

  • Randomized Controlled Trials: A randomized group of patients are assigned to an experimental group and a control group. These groups are followed up on for the variables/outcomes of interest.

Level III

  • Quasi-experimental Trial: Controlled trial with a nonrandomized group of patients. 

Level IV

  • Cohort Study: Identifies two groups (cohorts) of patients, one which did receive the exposure of interest, and one which did not. Follows the cohorts forward for the outcome of interest.
  • Case-Control Study: Identifies patients who have the outcome of interest (cases) and control patients without the same outcome and looks for exposure of interest.

Level V

  • Systematic Review: Appraised summary of all qualitative or descriptive research that addresses a specific clinical question.

Level VI

  • Case Report: Evidence form a single descriptive or qualitative study

Level VII

  • Expert Opinion: Descriptive study of a single case or series of cases with no research design or generalized information found in textbooks, encyclopedias, etc. 

CRAP Test

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C - Is the information current?

R - Is the information relevant/reliable?

A - Who is the author/authority?

P - What is the purpose/point of view?