Research Guides: Evidence-Based Practice: Acquire

Evidence Pyramid: Levels of Evidence

The "evidence pyramid" is often used to illustrate the levels of evidence in the literature. When beginning your search for evidence, begin at the highest possible tier.

Filtered Information is "pre-appraised." This means that the content has been filtered to include studies and reviews that are of higher quality. Keep in mind that the amount of available literature and the number of problems covered gets smaller as you move up the pyramid.

Unfiltered Information represents the original studies. These tiers may not contain studies of high quality and strong evidence, but they cover a much broader range of clinical problems and are much more available.

If you don't know where to begin, consider using a meta-search engine that simultaneously searches multiple websites to find the evidence.

Adaption of "Rating System for the Hierarchy of evidence for Intervention/Treatment Questions" by B. M. Melnyk and E. Fineout-Overholt, 2015, Making the case for evidence-based practice and cultivating a spirit of inquiry, In Evidence-Based Practice in nursing & healthcare: A guide to best practice (3rd ed., pp. 3-23). Wolters Kluwer. Copyright 2015 by Wolters Kluwer Health.

Filtered Information

Filtered information comes in a variety of forms, including systematic reviews, meta-analyses, guidelines (e.g., critically appraised topics). These works appraise the quality of studies on a particular topic, synthesize the studies' results, and may make a recommendation for clinical practice.

Cochrane Library
A collection of databases containing different types of high-quality, independent evidence to inform healthcare decision-making. The Library includes the Cochrane Database of Systematic Reviews (CDSR) which has the full text of the reviews of randomized controlled trials often combined with meta-analysis and the Database of Abstracts of Reviews of Effects (DARE). This resource is available thanks to the JABSOM Health Sciences Library.
PubMed Medline
Use the Article type filter in the left sidebar to limit results to Systematic Review, Meta-Analysis, Practice Guideline, and/or Guideline.
CINAHL with Full Text
Click on Advanced Search to see the Limit your results options. Select Meta Analysis, Meta Synthesis, Practice Guidelines, and/or Systematic Review from the Publication Type list. Hold down the CTRL key while selecting multiple options from the list.
ClinicalKey
Select Guidelines from the pull-down menu next to the search box OR click on the Guidelines box in the Browse clinical content section to browse by title, specialty, or authoring organization.

Database of Abstracts of Reviews of Effects (DARE)
Access critical abstracts of systematic reviews that evaluate the effects of health care interventions and the delivery and organization of health services. Due to the lack of funding, no new abstracts have been added to this resources since March 2015. From NHS's Centre for Reviews and Dissemination (UK). Unrestricted

DynaMedex
DynaMedex combines the clinical expertise and extensive, curated disease content of DynaMed with the comprehensive view into treatment options, depth and breadth of drug information and advanced search capabilities of Micromedex. Provide users with evidence-based insights for optimal clinical decision-making and improved patient outcomes. This resource is available thanks to the JABSOM Health Sciences Library.

ECRI Guidelines Trust™
Resource for finding evidence-based clinical practice guidelines. Unrestricted

Unfiltered Information

PubMed Medline
- Use PubMed's Clinical Queries feature to filter articles based on the clinical question category (e.g., Diagnosis) and on the preference for a Broad or Narrow search scope.
- Use the Article type section of the Filters sidebar and MeSH terms to limit results to systematic reviews, meta-analyses, randomized controlled trials, and other specific study types.
CINAHL with Full Text
- Click on Advanced Search to see the Limit your results options. Select an option from the Clinical Queries list based on the category of the clinical question (e.g., Therapy) and the preference for the scope of the subject (i.e., High Sensitivity, High Specificity, Best Balance).
- Use the Publication Type limit and subject headings to refine results to systematic reviews, meta-analyses, randomized controlled trials, and other specific study types.

Meta-Search Engines: Searching Multiple Sources

These search engines simultaneously search multiple websites to find the evidence to help you answer your clinical question.

Trip Database
Simultaneously searches multiple websites to find relevant information (e.g., systematic reviews and guidelines) to answer clinical questions using the best available evidence. Unrestricted access is also available.

Steps to Acquire Evidence

1. Identify search terms (i.e., keywords and subject headings) based on the answerable clinical question.

2. Identify synonyms or spelling variations for the search terms.

3. Combine key terms using Boolean Operators.

4. Use filters as needed.

5. Modify search as needed to adjust the results of the search.

Glossary of Studies

Definitions of selected types of studies are given below. For additional definitions, consult the references listed below.

Case Report
A detailed report of the diagnosis, treatment, and follow-up of an individual patient. Case reports also contain some demographic information about the patient (for example, age, gender, ethnic origin).

Case Series
A group or series of case reports involving patients who were given similar treatment. Reports of case series usually contain detailed information about the individual patients. This includes demographic information (for example, age, gender, ethnic origin) and information on diagnosis, treatment, response to treatment, and follow-up after treatment.

Case-Control Study
A study that compares two groups of people: those with the disease or condition under study (cases) and a very similar group of people who do not have the disease or condition (controls). Researchers study the medical and lifestyle histories of the people in each group to learn what factors may be associated with the disease or condition. For example, one group may have been exposed to a particular substance that the other was not. Also called retrospective study.

Cohort Study
A clinical research study in which people who presently have a certain condition or receive a particular treatment are followed over time and compared with another group of people who are not affected by the condition.

Randomized Controlled Trial
A controlled clinical trial that randomly (by chance) assigns participants to two or more groups. There are various methods to randomize study participants to their groups.

References
Agency for Healthcare Research and Quality. Glossary of terms. Retrieved from: http://www.effectivehealthcare.ahrq.gov/index.cfm/glossary-of-terms/
Note: Glossary of terms is no longer available.

National Cancer Institute. Dictionary of cancer terms. Retrieved from: http://www.cancer.gov/dictionary

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