Gathering PICO search terms

While collecting search terms, you look for the most commonly used English terms. We search in English because most of the research in the world is written in English, so you can find the most results when you use English terms.

It is good to collect some synonyms, because not all researchers use the same word to describe something.

If you have a search term that consists of multiple words, such as Alzheimer's disease, put "double quotes" around the words. This way the database knows that you want to search for exactly that combination of words, and not just for Alzheimer's and disease separately.

Another tip is that you can use truncation in many databases. This means that you are looking for different words that start with the same letters. Imagine that you want to search for assisted, but also for assisting and assist. Instead of writing down all these words, you can use truncation. After the letters that must match (assist-) write an asterisk (assist*). Now the database searches for all search terms starting with assist

Example gathering PICO search terms

It might help to gather the words in a table for better overview.


In the table below you see some examples of search terms that match the PICO.

P - elderly people with dementia I - supervised tooth brushing C - independent tooth brushing O - good oral hygiene
dementia "care staff" unassisted "oral health"
"Alzheimer's disease" assist* "oral self-care" "oral hygiene"
"cognitive impairment" autonomous "dental health"


UItleg AND, OR en NOT

To combine searches you use so-called Boolean operators. Most databases recognize OR, AND and NOT.

When you use OR, you will find publications that match one search term or the other or both search terms.
OR is used when you want to extend (OR=mORe).
E.g. "diabetes mellitus" OR diabetes

You use AND if the publications must match both search terms.
If you're looking for articles on physiotherapy for diabetes, use "diabetes mellitus" AND "physical therapy modalities", or even better:
("diabetes mellitus" OR diabetes) AND ("physical therapy modalities" OR "physical therapy").
BelangrijkWhen you combine AND and OR, make sure that the ( parentheses ) are correct.
With ("diabetes mellitus" OR (diabetes AND "physical therapy modalities") OR "physical therapy) you get very different results...

When you use NOT, you exclude all publications that match a search term.
Are you looking for articles about diabetes, but not gestational diabetes,
then you can use: "diabetes mellitus" NOT "gestational diabetes".
BelangrijkYou will not find articles that deal with both types of diabetes, even though they are also about your subject! So be careful when you use NOT that you don't filter out too much.

Also take a look at the (Dutch) PubMed Library Guide for more examples with boolean operators 

Building a PICO search string


When you have collected different search terms for the P, the I, possibly the C, and the O, it is time to combine them into a search string. This works as shown in the picture above. You don't necessarily have to have three search terms per part.


The complete search string of this example then looks like this:

("cognitive impairment" OR dementia OR "alzheimer's disease") AND ("training care staff" OR assist*) AND (unassisted OR "oral self-care" OR autonomous) AND ("oral health" OR "oral hygiene" OR " dental health")

To automatically include more synonyms in your search string, you can also add MeSH terms to your search string. Read more about what MeSH terms are and how to use them here.

With the search string you will search the databases in the next step. 

Handy Links

Here are some interesting links and other Library Guides for you to check out. The PubMed Library Guide is currently only available in Dutch