Levels of Evidence and Study Designs
Levels of evidence vary somewhat depending on the source you use. Two of the most commonly used levels of evidence in Nursing are from authors Melnyk and Fineout-Overholt and the Johns Hopkins Evidence-Based Practice Model, but they are not the only options that exist. Therefore, when indicating the level of evidence in a synthesis table or written narrative, ALWAYS clearly indicate whose evidence levels or grading system you are using.
- Levels of Evidence (Melnyk and Fineout-Overholt, 2023)Referenced on a guide from Amanda Pruka at Winona State University. Also includes levels of evidence as described by LoBiondo-Wood & Haber (2022).
- Levels of Evidence - Johns Hopkins Evidence Based Practice ModelA helpful guide from Cullom-Davis Library, Bradley University.
- Evidence Levels (Evidence Pyramids)This page of the evidence-based practice guide for DNP students provides links to various visual representations of the levels of evidence. Again, these vary slightly according to the system being used, but the basic hierarchy is the same.
- Study DesignsList of common (not exhaustive) study designs and definitions compiled by Advocate Health-Midwest Library
- Suggested Study Designs by Question TypeFrom Advocate Health - Midwest. Lists the study designs that are considered to fit best with each type of clinical question.
About the Cochrane Database of Systematic Reviews
- Search the Cochrane LibraryWright State University does NOT currently subscribe to the Cochrane Library, so we cannot access the current year's subscription-based content. However, the Cochrane Library is still searchable and Cochrane Reviews are still indexed for MEDLINE. Also, many Cochrane Reviews are available as open access. If you need a Cochrane Review that requires a subscription or fee, please contact your subject librarian.
About Cochrane
Cochrane produced this video explaining its mission and why it is important to healthcare.- Read about Cochrane's mission.
Cochrane Library (Cochrane Database of Systematic Reviews/CDSR) - Keyword Searching Using PICOA video overview of using the advanced search in Cochrane Library for clinical questions using the elements of a PICO question. The sample question has a nursing emphasis.
Cochrane Library - Clinical TrialsA video overview of the the Cochrane Library's Trials Register search results tab.
How to Search the Literature Using the PICO Question Format - CINAHL and PubMed
- CINAHL This link opens in a new window
Search journal literature related to nursing and the allied health disciplines. Also contains early-release citations for pre-published journal articles.
Strategies for Effective Searching, Part 1 by Part 1. This strategies introduction is split into two parts. It starts with a PICO(T) question and discusses how to brainstorm synonyms and when it is appropriate for particular PICO(T) elements to be included and excluded from database searches. The videos also review the use of truncation and Boolean operators in database searches.
CINAHL - Keyword Searching Using PICO by Video overview of using the advanced search in CINAHL for clinical questions using the elements of a PICO question. The sample question has a nursing emphasis.
CINAHL: Broadening Your Search by Describes one way to broaden your search if searching all of your PICO elements as keywords retrieves too few relevant results. The sample question has a nursing emphasis.
CINAHL - Subject Headings by Describes how using CINAHL Subject Headings can help you expand your PICO search if keywords alone do not get enough relevant results.
General CINAHL HelpWright State University's CINAHL Help Guide.
- PubMed This link opens in a new windowPubMed provides free access to the National Library of Medicine’s (NLM) premier database – MEDLINE. Content is citations and abstracts from national and international journals covering all aspects of biomedicine including allied health and other fields as they relate to medicine or healthcare.
Using PubMed in Evidence-Based Practice Training Course (HTML)When conducting research, evidence-based practice is a method for framing clinical questions that will help yield optimal search results. PubMed is a free research tool from the National Library of Medicine®. This course will show you how to use evidence-based practice when searching clinical questions using PubMed®.
Note: To search PubMed®, please use Wright State's link for PubMed rather than the PubMed.gov® URL to access Wright State and OhioLINK subscriptions to full text articles.
The scenarios used in this tutorial are geared toward nurses, but the tips for how to develop search strategies can transfer to any clinical scenario.
Duke University EBP TutorialDeveloped by the staff at Duke University Medical Center Library and the Health Sciences Library at the University of North Carolina at Chapel Hill. (Module 2: Acquire covers searching PubMed to find evidence). Distributed under the terms of the Creative Commons Attribution-NonCommercial-Share Alike license.
General PubMed HelpWright State University's PubMed Help Guide.
Filters/Hedges for Evidence-Based Literature Searching
- PubMed This link opens in a new windowClinical Queries - On the PubMed home page, click "Clinical Queries" under the heading "PubMed Tools".
Biomedicine focused, but includes some nursing and allied health. Covers 1950-present. Includes a clinical queries filter for searching therapy, diagnosis, etiology, prognosis, and clinical prediction guides (predictive value of tests). Clinical Queries filter is based on Research Methodology filters developed by Haynes RB et al. - CINAHL This link opens in a new windowClinical Queries appears as one of the search limiters within CINAHL. See the "CINAHL Clinical Queries" link below for more information about how these options work.
- CINAHL Clinical QueriesHelp guide for CINAHL Clinical Queries.
Distilled Information Sources
- Evidence Based NursingA journal, but the studies and reviews are summarized in "value-added" abstracts. See the journal's Purpose and Procedure document for more information.
- Resources for Foreground QuestionsAdditional tools linked on Wright State's Medicine: Evidence-Based Resources Guide.
Clinical Practice Guidelines
- ECRI Guidelines Trust (EGT)A public and free centralized online repository of evidence-based guidelines develeped from national and international organizations. (ECRI Institute had previously maintained AHRQ's National Guideline Clearinghouse until it was shut down in 2018 due to lack of funding). Inclusion Criteria
- AGREE EnterpriseThe Appraisal of Guidelines for Research and Evaluation (AGREE) Instrument and other tools.
- Guideline CentralClinical practice guidelines and decision-support tools database including guideline summaries, pocket guides, full-text guidelines, patient summaries, calculators, videos and more. Some (but not all) content is free. Ask your librarian for help if the content you need is not freely available.
- iCAHE Guideline ClearinghouseInternational Centre for Allied Health Evidence, University of South Australia.
- Clinical Practice Guidelines [additional sources and explanations]From the University of Texas Libraries. Links to other sources of clinical practice guidelines including national clearinghouses and professional societies. Also describes how to locate guidelines available in library databases.
Nursing-Specific Resources
- Evidence-Based NursingA journal, but the studies and reviews are summarized in "value-added" abstracts. See the journal's Purpose and Procedure document for more information.
- Sigma Repository (The Virginia Henderson International Nursing Library / Repository)"The Virginia Henderson Global Nursing e-Repository (Henderson Repository) is the only repository solely dedicated to sharing works created by nurses around the world. It is an open digital academic and clinical focused service that freely collects, preserves, and disseminates full-text nursing research, educational, and evidence-based practice materials in a variety of formats and item types. The repository is a resource of Sigma Theta Tau International (Sigma)."
Journal of PeriAnesthesia Nursing: Evidence to Practice Article Series
The following series is published in the Journal of PeriAnesthesia Nursing.
According to the authors, "the objective of this series is to identify EBP-related traditions that have been in existence for decades, some of which are outdated, while others are not grounded in evidence, and may just add confusion, poor scholarship, and a workload burden."
If using these links off campus, you will need to authenticate with your campus user name (w number) and password.
AJN Series: Evidence-Based Practice: Step by Step
These persistent links allow Wright State University users to access these articles through our subscription to AJN. Note: If off campus, you will be prompted for your campus w number and password before being taken to the article.
This collection of articles was authored by faculty from the Arizona State University College of Nursing and Health Innovation's Center for the Advancement of Evidence-Based Practice and published in the American Journal of Nursing (AJN)
JBI's Systematic Reviews Step by Step (published in the American Journal of Nursing)
A series on systematic reviews from the Joanna Briggs Institute, an international collaborative supporting evidence-based practice in nursing, medicine, and allied health fields. The purpose of the series is to show nurses how to conduct a systematic review—one step at a time. Published in AJN.
These persistent links allow Wright State University users to access these articles through our subscription to AJN. Note: If off campus, you will be prompted for your campus w number and password before being taken to the article.
Finding Systematic Reviews in Healthcare
- CRD (Centre for Review and Dissemination) DatabasesPublicly accessible web access to ABSTRACTS only the Cochrane Database of Systematic Reviews as well as from archived (no longer updated) versions of DARE, NHS EED, and HTA. Full text articles are NOT available.
- Centre for Reviews and DisseminationProvides guidance for developing reliable systematic reviews in healthcare and resources for review methods and evidence synthesis. (The "Guidance" and "Resources" links are recommended).
Grey Literature - What if the evidence I need is not published in a commercially available journal?
- CADTH (Canadian Agency for Drugs and Technologies in Health) EBP ResourcesProvides a variety of resources that enable you to find, produce, interpret, and implement evidence. These include software applications, search tools, customized Excel spreadsheets, and more.
- Grey Matters: A Practical Search Tool for Evidence Based MedicineCADTH's downloadable search tool to help guide and document grey literature searches.
- Grey literature in meta-analyses of randomized trials of health care interventions. (Cochrane Methodology Review).Hopewell, S., McDonald, S., Clarke, M., , & Egger, M. (2007). Grey literature in meta-analyses of randomized trials of health care interventions. Cochrane Database Syst Rev, no. 2, MR000010. doi:10.1002/14651858.MR000010.pub3
- State of the evidence reviews: advantages and challenges of including grey literatureBenzies, K. M., Premji, S., Hayden, K. A., Serrett, K. (2006). State-of-the-evidence reviews: advantages and challenges of including grey literature. Worldviews on Evidence-Based Nursing, 3(2), 55-61.. doi:10.1111/j.1741-6787.2006.00051.x
- Grey literature in meta-analysesConn, V. S., Valentine, J .C., Cooper, H. M. & Rantz, M. J. (2003). Grey literature in meta-analyses. Nursing Research, 52(4), 256-261. doi:10.1097/00006199-200307000-00008
- Grey Literature in the Health Sciences GuideAdditional resources for finding grey literature.
Types of Reviews in Healthcare - Articles
- Grant, M. J., & Booth, A. (2009). A typology of reviews: an analysis of 14 review types and associated methodologies. Health Information & Libraries Journal, 26(2), 91–108. https://doi.org/10.1111/j.1471-1842.2009.00848.xRequires authentication with w number and password. To access the full text, click the PDF full text link to the left of the abstract.
- MacEntee, M. I. (2019). A typology of systematic reviews for synthesising evidence on health care. GERODONTOLOGY, 36(4), 303–312. https://doi.org/10.1111/ger.12439Requires authentication with w number and password. To access the full text, click the PDF full text link to the left of the abstract.
Want to know more about the EBP Process?
- DNP Program: Evidence-Based Practice ResourcesAdditional resources about the various steps in the EBP process.
Evidence Evaluation Table - Template and Sample
- Evidence Evaluation Table TemplateCopy and paste from this template to create the columns for your own Evidence Evaluation Table. [Online-only content for “Critical Appraisal of the Evidence: Part I,” by Fineout-Overholt and colleagues in the American Journal
of Nursing, July 2010, p. 47-52] - Sample Evidence Evaluation Table - CompletedThis is an example of an Evidence Evaluation with all of the elements filled in. [Online-only content for “Critical Appraisal of the Evidence: Part III,” by Fineout-Overholt and colleagues in the American Journal of Nursing,
November 2010, p. 43-51.]
Selected Tools for Critical Appraisal and Grading the Strength of Evidence
Here are a few links you might find helpful for evaluating the evidence you find, but your professor may require you to use others. Please refer to your syllabus and ask your professor if you are uncertain if you need to use a particular set of critical appraisal tools. (Temple University Libraries compiled this list of tools and has a more extensive list of critical appraisal resources on its Critical Appraisal Guide).
Critical Appraisal Checklists and Worksheets for a Variety of Study Designs
Grading the Strength of Evidence
- GRADE ApproachGRADE: (Grading of Recommendations Assessment, Development & Evaluation) The GRADE Approach is used in a systematic review to make an overall recommendation of the evidence from strong to weak.
- GRADE CERQual(Confidence in the Evidence from Reviews of Qualitative Research): GRADE for qualitative systematic reviews to assess the evidence or develop recommendations.
- ConQual ApproachRating the confidence of qualitative systematic review findings. An article describing the approach.
Other Tools for Evidence Based Practice
Most of these resources are NOT nursing-specific.
- SumSearch 2Web-based search tool for finding medical and health care evidence. From the University of Texas Health Sciences Center at San Antonio (UTHSCSA).
- TRIP DatabaseSearch engine that collects results from a number of internet sites (mostly based in UK).
- ClinicalKey This link opens in a new windowClinical Overviews within ClinicalKey is an evidence-based clinical information source for primary health care providers. Includes tools for differential diagnosis, evaluation and management of medical conditions, patient education and procedure skills review. The differential diagnosis and medical condition files can be accessed on handheld devices via PocketConsult, a separate download available within the database.
- Evidence-Based MedicineLinks to additional Evidence Based Practice resources.
