Undergraduate Medical Education

1. Boolean Operators

There are three main Boolean operators: AND, OR, NOT. These work in most, but not all databases and some databases will have different syntax. Always check the database's help guide or user page to make sure you are using the correct Boolean syntax. 

• AND is used to combine different concepts and will retrieve articles that contain both terms (example: stroke AND physiotherapy)
• OR is used to combine synonyms of the same concept and will retrieve articles that contain at least one of your terms (example: stroke OR cerebrovascular accident)
• NOT is used to exclude a concept and will retrieve articles that include one term but not the other (example: uterine hemorrhage NOT menorrhagia)
  • It is not recommended to use NOT, especially in searches for knowledge syntheses, as you could be eliminating relevant articles.

2. Parentheses

Parentheses are used to set the order of the search. Like in math, parentheses are taken into account first, and the databases will search for that query before executing the rest of the search.

Example: (ultrasound OR ultrasonography OR echography) AND (leiomyoma OR uterine fibroid OR fibromyoma)

3. Truncation

Truncation helps you limit the number of individual search terms you have to enter by taking the root of the word and applying variations to it. For example, if you want to search for surgery or surgeries, you can simply use a truncation symbol on the root "surger". Truncation symbols vary depending on the database, but the most common form is the asterisk (*). Example: surger*

In order to make searching easier and get a sense of which terms are retrieving the most results, it is recommended that you enter one search term at a time. Also, it is easier to build one concept at a time (your ORs) and then combine your the different concepts at the end (your ANDs).

For more information on searching in medical databases, please see the Health Sciences Literature Searching Basics

Once you've decided on a research question, it can be tempting to dive right into a database and start looking for articles. It's important to take the time to think about your search and have a thorough plan. This will make the search a lot easier and ensure that you aren't missing important articles.

1. Key concepts

Take a look at your question and extract the concepts that are the most important. These are elements that articles must have. 

2. Subject Headings

A lot of medical databases have subject headings, or controlled vocabulary, that is used to index, or tag, articles. Your concept will sometimes, but not always, have a corresponding subject heading that you should search with. Subject headings change across databases - always consult the database's list before proceeding.

For more about subject headings, please click here. 

3. Keywords

Searching for words in the title, abstract or the author-provided keywords of an article is called keyword searching. Once you have determined your key concepts and matched them to the appropriate subject heading, it's time to think of all the different ways they can be described. There can be geographical and cultural differences that affect the way concepts are described. Are there technical terms, plural forms, acronyms, etc. Make a thorough list before entering your terms into the database.

*Note: it is important to search for both keywords AND subject headings as they complement each other. For more information about searching for both, please consult our Health Sciences FAQ on the topic.