Guide to Researching

PICO Search Terms

One useful way of structuring scientific research is to divide your focus into four sections: problem, intervention, comparison, and outcome (PICO). This facilitates selecting language and key terms for your computerized search of research sources.

  • Problem or Population—focuses on a particular problem, a disease, a type of patient, or a particular symptom.
  • Intervention—focuses on a particular treatment or exposure.
  • Comparison—identifies alternatives to the intervention.
  • Outcome—specifies the desired or expected outcome.

There are many guides to the PICO research method on the internet, such as Health Links' "Construct Well-Built Clinical Questions using PICO" article, and the University of Toronto's "Formulating Answerable Questions" guide.

Creating and Using Key Words

Once you have a topic that is adequately focused and narrowed, it is helpful to create a list of key words to facilitate searching for resources. It will also help keep track of searches you’ve done by ensuring that the same keywords are used in all the databases you’ve searched (i.e., internet search engines, journals, library catalogues, etc.). It is also a good idea to think about possible synonyms and alternative phrases for the key words in order to do a more comprehensive search.

Using the Correct Operators


  • A symbol that represents the intended relationship between the keywords used in a search.

Boolean operators:

  • The operator AND indicates that the keywords must be found together.
  • The operator OR indicates that either, or both, of the keywords must be found.
  • The operator NOT allows you to exclude certain words in the search.

Remember that even with a set list of keywords, internet database searches won't be as precise as you might want. Using the correct operators in the keyword search significantly narrows down material and saves a lot of time. To access a guide to properly using operators, see "WWW Research Guide: Search Engines 1." It addresses the use of special operators, including Boolean logic, to focus keyword searches.

Organizing Your Thinking

For an unfamiliar topic, a good strategy is to write down a list of questions. Just identifying what it is you don't know about the subject is often half the battle. Having a list of questions will help you create your search criteria, formulate specific questions to ask others, and often even give you the answers you seek.

Search Engines

Some search engines, such as the Evidence-Based Dentistry Search Engine, provide PICO search terms right in their search function.

PubMed uses MeSH terms, which are explained in the PubMed/Medline Tutorial.

Additional Resources

How to Research Your Dentistry Essay was created by Margaret Fulford, the Faculty Librarian for the University of Toronto Faculty of Dentistry: "This online tutorial for University of Toronto students includes practical suggestions, examples, search tips, and links to useful resources."