Evidence Based Nursing is defined as the incorporation of the best research evidence along with patient preferences, the clinical setting and circumstances, and healthcare resources into decisions about patient care (Ciliska, 2006). This guide will help you understand how and where to find evidence based information.
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Before beginning a database search for evidence based information, write out your research topic as a focused question that summarizes what you're looking for. This important step helps you articulate your thoughts and helps you identify what you need before you begin searching for information. This saves you time and helps you create a targeted and organized database search.
You will want to include some very important concepts when formulating your question. The PICO mnemonic will help you identify the key concepts in your topic. These concepts will eventually translate into the search terms that will be incorporated into your database search. Need a refresher on the basics of constructing a database search statement? This handout will help.
Use the PICO worksheet to identify the important concepts in your research topic. Don't forget to brainstorm synonyms and create a word bank of potential search terms. Searching with synonyms is the key to finding good information!
P (Patient population) What are the patient’s most important characteristics? (Consider their age, gender, culture, and setting) or P (Problem) What is the primary problem?
I (Intervention) What main intervention are you considering?
C (Comparison) What will the main intervention be compared to?
O (Outcome) What are you trying to accomplish?
Questions related to the care of a patient typically fall into defined clinical scenarios or clinical categories. You will want to identify which category your research question falls under when searching for evidence based information.
Why is this important? Because each scenario is best addressed by a specific type of study. Identifying the clinical scenario helps you understand which types of studies to look for in a database. Some databases like CINAHL and PubMed MEDLINE even have filters that allow you to limit your search according to your clinical scenario! That saves you time and energy.
Common scenarios include: Therapy (Intervention), Diagnosis, Etiology/Harm, Prognosis, and Meaning
Melnyk and Fineout-Overholt (2015) provide guidance on which types of studies best address these scenarios. The studies are listed in order of strength, with the strongest source of evidence listed first (level 1). Synthesis or compilations of multiple studies typically provide the best evidence and are always level 1.
Therapy (Intervention) or Diagnosis
1. Systematic review or meta-analysis of randomized controlled trials (RCTs)
4. Cohort studies or case-control studies
5. Meta-systhesis of qualitative or descriptive studies
6. Qualitative or descriptive single studies
7. Expert opinion
Etiology/Harm or Prognosis
1. Synthesis of cohort study or case-control studies
2. Single cohort study or case-control studies
3. Meta-synthesis of qualitative or descriptive studies
4. Single qualitative or descriptive studies
5. Expert opinion
1. Meta-synthesis of qualitative studies
2. Single qualitative studies
3. Synthesis of descriptive studies
4. Single descriptive studies
5. Expert opinion
There are many types of research studies found in the published research literature. This hierarchy of evidence represents some of the more common types of quantitative studies that students will find in databases such as CINAHL or PubMed MEDLINE.
This Hierarchy of Evidence was adapted from Duke University's Introduction to Evidence-Based Practice tutorial.
What does it all mean?
Meta-Analysis: Works that summarize the results of multiple studies on a topic and mathematically combine the results using accepted statistical methodology to report the results as if it were one large study.
Systematic Reviews: A summary of evidence on a particular topic that uses a rigorous process (to minimize bias) for identifying, appraising, and synthesizing multiple research studies. Examples of these types of reports can be found in the Cochrane Library database.
Randomized Control Trials: A true experiment that delivers an intervention or treatment in which subjects are randomly assigned to control and experimental groups. RCTs are the strongest design to support cause and effect relationships.
Cohort Studies: Longitudinal studies that begin with two groups of patients (the cohorts), one that received an exposure and one that does not. The groups are then followed over time to measure the development of different outcomes. Cohort studies are observational and the two groups may differ in ways other than the variable under study.
Case-Control Studies: Studies in which patients who already have a specific condition are compared with people who do not. The researcher looks back to identify factors or exposures that might be associated with the illness. They often rely on medical records and patient recall for data collection. These types of studies are often less reliable than randomized controlled trials and cohort studies because showing a statistical relationship does not mean than one factor necessarily caused the other.
Case series and Case reports: Collections of reports on the treatment of individual patients or a report on a single patient. Because they are reports of cases and use no control groups to compare outcomes, they have little statistical validity.
Animal Research: Studies that use animals as investigational subjects.
Definitions for these and other studies can be found in the book Evidence-based practice in nursing & healthcare by Bernadette Melnyk and Ellen Fineout-Overholt and in Duke University's Introduction to Evidence-Based Practice tutorial.
TIP: Students will often encounter studies that are not found on a hierarchy of evidence. One way to determine the level of evidence for these studies is to refer to a book on research methods or evidence based practice for nursing. These Alverno texts will help you appraise the strength of evidence for studies not represented on a hierarchy of evidence.
The best research evidence for a topic is typically found in the published research literature - which Alverno students can access through the library's databases. The PICO worksheet will help you brainstorm search terms and develop an organized search strategy.
Alverno librarians recommend these databases for finding evidence based information: CINAHL, PubMed MEDLINE, and the Cochrane Library.
You will need the 14 digit barcode found on your Alverno student ID if logging in from off campus.
Need more information? Use the tabs located above this box for some helpful tips.
CINAHL (Cumulative Index of Nursing and Allied Health Literature) provides access to a wide range of articles published in the nursing journals. CINAHL is found on the Databases by Subject or Databases A-Z page. Students can use the database's Advanced Search feature to limit a search to evidence based resources.
First, a word of caution. Adding Advanced Search "limits" to a database search lowers the number of articles you will retrieve. Adding too many "limits" can result in very few or even zero articles.
Tips for using CINAHL's Advanced Search feature:
1. From the CINAHL homepage, click the Advanced Search link just beneath the search box. This will bring up a screen with multiple limits (filters) that can be incorporated into an CINAHL search. Several of these allow you to limit your search to evidence based resources only.
2. The Clinical Queries filter allows you to select and limit a search using some of the common clinical study categories.
3. The Evidence-Based Practice filter allows you to simply check a box and limit a search to evidence based resources.
4. Finally, there is a box titled Publication Type. This allows users to select and limit a search to a specific type of research study. For example, you could limit a search to Level 1 synthesis reports such as meta-analysis or systematic reviews. Hold down the Ctrl key on your keyboard to select more that one publication type.
This powerful and comprehensive database provide access to citations for millions of articles published in the biomedical research literature. The database has multiple features that allow users to refine a search - including Clinical Queries, which allows users to limit to evidence based resources only.
PubMed MEDLINE is a free database available to anyone with an internet connection. Alverno students should always access this database through the library's website. This will provide access to publications found in Alverno's subscription databases, as well as articles available free to the public.
Tips for using PubMed's Clinical Queries:
2. From the PubMed homepage, click the Clinical Queries link located towards the center of the page and enter your search terms in the search box.
3. PubMed will apply two filters (Clinical Study Categories and Systematic Reviews) to retrieve citations for evidence based articles from the MEDLINE database.
4. The Clinical Study Categories column displays citations filtered to a specific clinical study category. By default, articles related to therapy will display. Use the drop down menu to change the clinical category.
5. The Systematic Review column displays citations for systematic reviews, meta-analyses, reviews of clinical trials, and other evidence-based resources.
6. Review the citations and click on a link to access the article's abstract. If you accessed the database through the library website, you should see a blue "Online Full-Text" icon if the article is available in an Alverno database.
7. Need help maneuvering through PubMed? The National Library of Medicine provides tutorials that will help you understand how to use this powerful database. Alverno librarians recommend the "Quick Tours". These are perfect for busy nursing students and provide just the right amount of information for most research needs.
The Cochrane Library is a collection of six databases that contain different types of high-quality, independent evidence to inform healthcare decision-making. The jewel among these databases is the Cochrane Database of Systematic Reviews.
First, a word of caution: The Cochrane Database of Systematic Reviews is a fairly small collection and it's possible that a Cochrane review may not exist on your topic - especially if it's obscure.
Tips for searching the Cochrane Database of Systematic Reviews:
1. The Cochrane Library database is fairly easy to search. Simply enter your search statement in the default search box and click "Go". Your results will include only Cochrane systematic reviews - if they exist for your topic.
2. The Cochrane Database of Systematic Reviews labels each review as either Protocol or Review. A Protocol icon indicates a plan or set of steps to be followed in a study (the review is not complete). A Review icon indicates that the Cochrane review has been completed.
3. The Cochrane Database assigns other icons to clarify the status of a review. Definitions for each icon type are listed below:
Ciliska, D. (2006). Evidence based nursing: How far have we come? What’s next? Evidence Based Nursing, 9(2), 38-40.
Introduction to evidence-based practice. (2014). Retrieved from Duke University Medical Center Library & Archives website: http://guides.mclibrary.duke.edu/ebmtutorial
Melnyk, B. M., & Fineout-Overholt, E. (2015). Evidence-based practice in nursing & healthcare. Philadelphia, PA: Lippincott.