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The Ohio State University

Health Sciences Library

Medical Laboratory Science

Search Term Development

When searching the literature, you want to make sure you are searching for all the possible variations and different words that could be used to describe your topic.  For example, using both the terms cavities and dental caries.

  • Use the concepts you identified in your PICO question to help brainstorm search terms for your search.


  • Determine which concepts are primary concepts (i.e. which concepts are the most important).  Depending on your topic, you may not need search terms for every concept.


  • For each primary concept, think of as many different ways to describe the concept as you can.

PICO Keyword Chart

Synonyms are an important part of developing a thorough search strategy.

Subject Headings & Keywords

Each database will have its own special set of terms or SUBJECT HEADINGS that the indexers use to describe articles.  When developing your search strategy, it is always a good idea to take a look at the subject headings for that database to ensure you are using the official term, as well as to get ideas for synonyms or alternative search terms to use.  Below are descriptions of some of the commonly used subject headings.

  • Used by the National Library of Medicine to index MEDLINE/PubMed, MeSH stands for Medical Subject Headings.  
  • MeSH terms are organized in a tree structure that moves from more general to more specific. 
  • Each term will have "Entry Terms", which are synonyms that PubMed will automatically map to the MeSH term when searched. 
  • To search the MeSH database, select MeSH from the drop down menu next to the search box, or select MeSH Database under More Resources on the PubMed homepage. 


CINAHL Headings
  • These are the subject headings used within the CINAHL database. 
  • They are often the same as the MeSH term used in PubMed, but they can be different. 
  • To access the CINAHL Headings, click the link at the top of the database screen.  If you are searching more than one Ebsco database, you can hover your mouse over Subjects, then select CINAHL Headings from the list. 

In addition to searching with subject headings, you want to also include any synonyms or similar KEYWORDS in your search.  This is important to catch any results that may have been indexed with a different subject heading.  In some databases, it will also help catch results that may not have been fully indexed yet (this is especially important in PubMed).

  • Different people can use different words to describe the same thing. 
  • In searching, keywords can be any word or acronym that is used to describe a concept or idea. 
  • Common variations can include spelling (pediatric vs paediatric), abbreviations (left ventricular assist device vs LVAD), technical/medical terminology (heart attack vs myocardial infarction), and synonyms (teenager vs adolescent). 

Boolean Operators

The databases will often not understand your query if you enter it as a natural language sentence, such as your full research or PICO question.  Instead, you want to use the search terms that you brainstormed to create an advanced search strategy.  By using Boolean Operators, you can tell the databases precisely how you want your search terms to be searched. 


  • Limits your search to articles that contain both of the search terms
  • Narrows or focuses your search; you will typically get fewer results the more ANDs you use
  • Use AND between different concepts
  • For example: dental anxiety AND music therapy
                         Boolean And Diagram


  • Expands your search to articles that contain either of the search terms
  • Broadens your search; you will typically get more results the more ORs you use
  • Use OR between different search terms for the same concept
  • For example: dental anxiety OR dental fear OR dental phobia
                         Boolean Or Diagram


  • Excludes a term from your search
  • Narrows or focuses your search; you will typically get fewer results the more NOTs you use
  • For example: music therapy NOT art therapy
  • BE CAREFUL!  It is very easy to exclude too much and accidentally miss important and relevant literature.
  • Try to use combinations of AND and OR, then exclude results yourself, instead of using the Boolean NOT
                         Boolean Not Diagram


Lastly, when creating a more complicated or advanced search, you can use parentheses to group your keywords together and tell the database precisely how you want the terms searched.  The database will perform the searches within parentheses before the searches outside of parentheses.  This is similar to the way parentheses are used in math.

Use parentheses any time you have more than one keyword for a particular concept.  In other words, when you are using the boolean operator OR, put parentheses around all of the OR'd terms.

For example: (dental anxiety OR dental fear OR dental phobia) AND (music therapy OR music)