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Capstone and PICO (T) Project Toolkit: 5. Filtering the Evidence

Guide to locating research for evidence synthesis projects and assignments.

Filtering the Literature for Research Studies

Limits to use:

  • Database limits may include choices for filtering Publication Types (case studies, editorials, news articles, as well as higher levels of evidence such as clinical trials, systematic reviews, and meta-analyses). Limiting by publication type is one way to ensure that the research retrieved was based on a more rigorous methodology and thus reflects a higher level of evidence.
  • Date of publication limits can help reduce your set of results, particularly helpful when you have too many results, or you wish to retrieve only the most recent literature.
  • Age group: Using these limits ensures a standard approach to narrowing your search, (rather than using your own keywords such as "elderly" or "pediatric").
  • "Peer-reviewed articles," "research," "evidence-based," language, species,  and other subsets for topics may be available. Use with care, and be sure to read the description of what they mean, as they may inadvertently apply limits you don't want!

Limits to avoid:

  • "Full text" or "full text available," limits may appear and you should avoid using these!  NYU subscribes to full text in many ways and from multiple vendors and packages.  Look for the NYU full text links.  

More limiting strategies in CINAHLPlus:

  • In the CINAHL database, there is a limiter for “research article.” When applied, your search is limited to articles that are about a research study or examination of subject matter that uses investigational or experimental techniques.  A research study includes data collection, subject selection, methodology, discussion of results, and application, if any. For materials about or how to conduct a research study see the specific CINAHL subject headings such as Nursing Research or Research, Medical.
  • Limit to publication type: Systematic Review (indicates a research process in which a concept is identified and the research which has studied it is analyzed and evaluated. Results are synthesized to present the current state of knowledge regarding the concept. Includes integrated or integrative reviews).
  • Browse the many Publication types; notice the range from case study or letter (lower levels of evidence) to Systematic Reviews and Clinical Trials (higher levels of evidence).
  • Using the CINAHL “Evidence-based Practice” limiter includes “Research” articles (including systematic reviews, clinical trials, meta analyses, etc.)  as well as articles from evidence-based practice journals, articles about evidence-based practice, and commentaries on research studies (applying practice to research). Use with caution; every result may not be an evidence-based study. More about the evidence-based practice limiter.
  • Advanced Searches: 
    • Limit using Clinical Queries filter in five research areas:  Therapy, Prognosis, Review, Qualitative, Causation (Etiology)–A detailed explanation of the strategies behind these limits can be found on the Hedges page at McMaster University's Health Information Research Unit.
    • High Sensitivity is the broadest search, to include ALL relevant material. It may also include less relevant materials.
    • High Specificity is the most targeted search to include only the most relevant result set, may miss some relevant materials.
    • Best Balance retrieves the best balance between Sensitivity and Specificity.

Limiting to "Peer Reviewed" Articles

"Peer-reviewed" or "refereed" journals are those that subject content to a critical review by other experts in the field prior to accepting a manuscript for publication. Limiting your literature search to the peer-reviewed journals ensures a higher level of scholarship and research methodology. 

Magazines, trade journals, and newspapers tend to be "non-peer-reviewed," meaning perhaps just the editor or someone who is not an expert in the field has reviewed the content before publishing. 

Some article databases (not all) will have a filter (or "Limit") available for "peer-reviewed." Look for this feature in Proquest Central and CINAHL. 

How do you know if a journal citation is from a peer-reviewed journal?

  • You can do a journal title search in Ulrich's Global Serials Directory. There is a specific symbol ( Black and white referee's jersey icon. ) that indicates a journal is "refereed."
  • You can look for the "Limits" feature in many databases to narrow search results by publication type.
  • An individual journal's website may describe the peer review process and policies - look for sections like "For Authors" or "Editorial Policies"