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Evidence-based Practice Databases

Decorative image of evidence based practice pyramid

Using a PICO/T Question for Searching the Literature

PICO/T is a way to format a research question. It can also get you started with keywords for your literature search (state of the science)

P = Population of interest (consider age, gender, race, ethnicity, disease process, comorbidities)

I = Intervention (exposure to disease, prognostic factor A, risk behaviors, treatment, what do you want to do for this population? what could be done better?)

C = Comparison of interest (no comparison, placebo, prognostic factor B, absence of risk behavior, other treatments - "gold standard")

O = Outcome of interest (what result are you looking for? risk of disease, rate of occurrence of adverse outcomes like illness, comorbidity, or death)

T = Time (how long does it take to demonstrate an outcome? how long are participants observed? - if relevant to your question)

s = Study types (if relevant to your question)


1. P = menopausal women;  I = cranberry juice; C = no cranberry juice; O = incidence of UTI

In menopausal women, does drinking 1 cup of cranberry juice daily versus not drinking any cranberry juice lower the incidence of urinary tract infections?

Initial Keywords: menopause, cranberry juice, urinary tract infections

2. P = adults with arthritis; I = tomatoes; C = No comparison; O = increased joint pain

Do tomatoes worsen joint pain in adults with arthritis?

Initial Keywords: tomatoes, arthritis, pain


Godshall, M. (2016). Fast facts for evidence-based practice in nursing (2nd ed.). Springer Publishing Company. DOI 10.1891/9780826194077

Levels (Hierarchy) of Evidence

Photo by Alpha Stock Images - Creative Commons 3 - CC BY-SA 3.0

Level I:

Meta-analysis; Systematic Reviews of Randomized Controlled Trials (RCT)

Level II:

Randomized Controlled Trial (RCT)

Level III:

Quasi-experimental Studies (Controlled trials without randomization)

Level IV:

Cohort Studies (epidemiologic); Case-controlled Studies (epidemiologic)

Level V:

Systematic reviews of Descriptive Studies; Systematic reviews of Qualitative studies (meta-synthesis); Correlational Studies

Level VI:

Single Descriptive Study; Single Qualitative Study; Case Series Studies; Case Reports; Concept Analysis

Level VII:

Opinion; Reports of Expert Committees; Manufacturer's Recommendations; Traditional Literature Reviews

Based on: Schmidt, N. A., & Brown, J. (2019). Evidence-Based practice for nurses: Appraisal and application of research (4th ed.). Jones & Bartlett Learning.

EBP Filters in PubMed

Article Types / Publication Types:

(the following will allow you to limit to evidence based practice)

Clinical Study: automatically includes Clinical Trial, Controlled Clinical Trial, Randomized Clinical Trial, Observational Study

Comparative Study = comparison of outcomes, results, etc for different techniques, therapeutic approaches or other inputs.

Meta-Analysis = (multi-study) - studies using a quantitative method of combining the results of independent studies and synthesizing summaries and conclusions which may be used to evaluate therapeutic effectiveness. 

Multicenter Study = a study executed by several institutions

Systematic Reviews = (multi-study) - review of primary literature that attempts to identify, appraise, and synthesize all empirical evidence that meets specified eligibility criteria to answer a given research question. Systematic Reviews are NOT the same as Literature Reviews. Literature Reviews are NOT EBP.

Evaluation Study = studies determining the effectiveness of processes, personnel, and equipment

Validation Study = research using processes by which the reliability and relevance of a procedure for a specific purpose are established

Practice Guidelines: most are EBP, but some are still opinion-based. You will need to review the guideline to ensure it is EBP.

Epidemiologic Studies in PubMed:

  • Use Epidemiologic Studies as a search term for studies that examine associations, hypothesized causal relations. They are usually concerned with identifying or measuring the effects of risk factors or exposures. Includes: Cohort Studies, Longitudinal Studies, Prospective/Retrospective Studies, Case Control Studies, Cross Sectional Studies.

Qualitative Research in PubMed:

  • Use the following search terms to capture the various types of qualitative studies: Qualitative Research, Grounded Theory, focus groups, phenomenology, ethnography, nursing methodology research, narration, narrative, interviews as topic, "thematic analysis 

Resources for Appraising a Research Study


Qualitative Research Aids

Evidence Based Practice Websites

How to Write a Literature Review

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Doing a Literature Review in Health and Social Care

Aveyard, H. (2010; 2nd ed.)
Unlimited access ebook

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Doing a Literature Review in Nursing, Health and Social Care

Cronin, P., Coughlan, M., & Ryan, F. (2013)
Call number: RT 81.5 .C68 2013
Print book

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Doing Your Literature Review: traditional and systematic techniques

Jesson, J., Matheson, L., & Lacey, F. (2011)
Call number: H 62 .J44 2011
Print book

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Succeeding in Literature Reviews and Research Project Plans for Nursing Students

Williamson, G.R. & Whittaker, A. (2014)
Call number: RT 81.5 .W493 2014
Print book

Research Books: Critiquing, and Understanding

Library and Database Help