LibGuides: UPSMN Ring: Acquire Evidence

Search the Literature

After defining your PICO question, your next step in the EBM process is to search for literature that can help address it.

When building your search strategy, you will want to use a number of synonyms to describe each of your concepts to ensure you are not missing relevant literature. You will also use Boolean operators and parentheses to tell the database precisely what you are looking for.

Searching the Biomedical Literature
This video from Part 1 can provide a refresher on how to search in PubMed and Embase.
PubMed demo begins at 11:14, Embase demo begins at 29:03
These videos are restricted to med students with Echo360 login access.

Subject Headings & Keywords

What is a Subject Heading?

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.

MeSH

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.

Emtree

The database Embase uses their own subject headings called Emtree.
These terms are also organized in a tree structure and have many synonyms included in the entry.
The Emtree terms often differ from the MeSH terms (e.g. they use natural language, instead of inversion), but the corresponding MeSH term is typically mapped to the Emtree term as a synonym.
To search for terms in Emtree, click on the Emtree link at the top of the Embase search screen. Embase will also typically suggest the Emtree term as you type keywords into the search box.

What is a Keyword?

In addition to searching with subject headings, you want to also include any synonym or similar keywords in your search. These are the terms that you might see in the titles and abstracts of the articles.

This is important to catch any results that may have been indexed with a different subject heading than you would expect.

In some databases, it will also help catch results that may not have been fully indexed yet (this is especially important in PubMed).

Keywords

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 keywords to be searched.

AND

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: developmental disabilities AND music

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: developmental disabilities OR IDD

NOT

Excludes a term from your search
Narrows or focuses your search; you will typically get fewer results the more NOTs you use
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

Parentheses

Lastly, when creating a more complicated or advanced search, you can use parentheses to group your search terms 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 search term 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: (developmental disabilities OR intellectual disabilities OR idd) AND (music OR art)