Skip to Main Content
It looks like you're using Internet Explorer 11 or older. This website works best with modern browsers such as the latest versions of Chrome, Firefox, Safari, and Edge. If you continue with this browser, you may see unexpected results.

Health (Nursing, Medicine, Allied Health)

Guide to research sources and tools for locating health evidence in books, journals, databases.

Strategies for Narrowing a Search

If a database search returns too many results to be useful, there are a few methods you could try for narrowing the search.

1. Apply Database Filters

Publication Date

For many healthcare related questions, you will be primarily interested in the most recent information, so it is common to apply filters to only show results from the last 5 or 10 years.  


If your patient population has a particular age designation, many of the health sciences databases allow you to apply a filter for the age group that was studied in the article

Peer-Reviewed / Research Article

Many databases allow you to limit a search to only peer-reviewed articles, or articles that were published in scholarly journals.

(For more information about how to determine if an article is peer-reviewed, see "Limiting to 'Peer Reviewed' Articles" below)  

In addition to having a filter for 'peer reviewed articles', CINAHL has a filter that allows you to limit to only 'Research Articles', which are articles that report research study or examination of subject matter that uses investigational or experimental techniques (i.e. includes data collection, subject selection, methodology and discussion of results)

In CINAHL limits for Peer Reviewed and Research Article are found on the left side of the results page

Publication Type

Some databases allow you to filter by publication type or study methodology (e.g., 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.

  • PubMed permits filtering by 'Article Type' to located articles describing particular study methodologies 


Clinical Queries

PubMed and CINAHL have filters for "Clinical Queries" - pre-formulated search strategies ("hedges") that can be applied to your search to retrieve only clinically sound studies.

*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.  

2. Add Additional Concepts with AND

If an initial search retrieves too many results, it may be necessary to integrate an additional concept, using the Boolean operator AND.  For example, if you are search on a PICO question, you may consider integrating the O (outcome of interest) into the search strategy.

Narrowing a PICO database search by adding the 'outcome' concept with AND
Search Query: Number of Results Returned:
type II diabetes AND telehealth 556
type II diabetes AND telehealth AND blood glucose 195

3. Adjust Your Subject Headings

Choose Narrower Subject Headings

Subject headings are often hierarchical, with broader headings encompassing more specific terms.  For instance, while a search with the MeSH term "Diabetes Mellitus" may be too broad, you could try a narrower term like "Diabetes, Gestational".

An example of the hierarchy of terms in the MeSH thesaurus (broader and more specific diabetes terms)

Use Sub-Headings / Qualifiers

Some databases, like CINAHL and PubMed, allow you to append sub-headings to the subject terms, allowing for a narrower search.  For instance, if you were interested in the use of insulin, but only in the context of treating diabetes, you could apply the sub-heading "therapeutic use" : "Insulin / therapeutic use"

Also see:

Filtering the Evidence in PubMed

See this PubMed help page for accessible instructions on applying filters in PubMed.  

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. 

See this tutorial for more information about Peer Review in the Health Sciences.

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"