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A Guide for Nurses and Nursing Students

Where Should I Look For Evidence?

Depending on your PICO question, there are some publication types you can focus on to answer your question:

Most Clinical Questions:  Meta-analysis, Systematic Reviews

Therapy:  Randomized Control Trials

Diagnosis:  Prospective, blind controlled trials compared to a gold standard

Prognosis:  Cohort Study, Case Control, Case Series or Case Reports

Prevention:  Randomized Control Trials, Cohort Studies, Case Control

Etiology/Harm:  Randomized Control Trials, Cohort Study, Case Control

Cost Analysis:  Economic Analysis

Where Does the Publication Type show on an indexed article?

When you are determining which category an article falls under, there are some things you should consider.  This document with screenshots offer tips for assessing the level of evidence from five different articles in PubMed.

Examples of Publication Types in PubMed



Rating System for the Hierarchy of Evidence


Level I:  Systematic review or meta-analysis of randomized control trials (RCTs)

Level II:  RCTs

Level III:  Controlled trials without randomization (also called quasi-experimental studies)

Level IV:  Case-control and cohort study

Level V:  Systematic review of descriptive or qualitative or mixed methods studies

Level VI:  A single descriptive or qualitative study or mixed methods study

Level VII:  Experiential and non-research evidence, case reports, or case series

Level VIII: Expert opinion or evidence summaries

Adapted from the following two sources:

Fineout-Overholt, E., Melnyk, B.M., Stillwell, S.B & Williamson, K.M. (2010). Critical appraisal of the evidence: Part I. American Journal of Nursing, 110(7), 47-52.

Dang, D., & Dearholt, S. (2017). Johns Hopkins nursing evidence-based practice: model and guidelines. 3rd ed. Indianapolis, IN: Sigma Theta Tau International.

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