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Comprehensive Searching for Health Sciences: Searching

Where to Search?

You will most likely want to begin your search in the CINAHL database. CINAHL stands for Cumulative Index to Nursing and Allied Health Literature, and is an organized collection of scholarly articles coming from over 3000 journals. This database has literature that is specific to nursing and allied health topics in particular.

You may also want to look in the MEDLINE (EBSCO) database, especially if you need more articles. MEDLINE has literature about medicine and biomedical sciences, and indexes many more articles than CINAHL does. While it is not specific to nursing and allied health, it may have some additional articles on your topic.

To find CINAHL and MEDLINE, visit the BCIT Library home page, and click on "Online Databases", in the "Search" menu on the right-hand side of the page. Click on the A-Z list of databases, and scroll through the list. These databases are accessible both on campus or at home (when you sign in with your BCIT A-number).

If you are doing a very thorough search of the literature, you may also wish to search for "grey literature". Grey literature refers to documents that that have been created by an entity whose primary purpose is not in publishing, and which have not been published or distributed through traditional channels. The documents can not be found in a usual search, and might include government documents, conference proceedings, reports, preprints, speeches, graduate theses, and more. 


The keywords you use will be single words or phrases that you have selected to represent an element of your PICO. If your P is patients who have suffered a heart attack, your keywords might be "heart attack" or "myocardial infarction". If your I is exercise, your keywords might be exercis*, "physical activity", "strength training", "aerobic activity", etc. 

When you do a keyword search, the database looks for those exact keywords to be present in the article title, abstract, and subject headings. Most databases (including CINAHL and MEDLINE) do not search for keywords in the full text of the article.

Try to think of multiple ways to represent your topic through different keywords. The more relevant keywords you use, the more articles you are likely to find.

Boolean Operators

We separate terms in our search using the word (operator) OR when we want any or all of those terms in our search results. "OR is More", as they say - by using OR, we catch more articles, even when different authors use different terminology to talk about the topic. OR helps us connect multiple terms that are all about the same topic.

For example, if our P is preterm infants, it would be helpful to search for preterm infants OR premature infants so that we find articles that use either terminology. Just searching for preterm infants alone may miss some relevant articles that refer to preterm infants.



We separate different concepts in our search using the word (operator) AND. AND narrows down the search results by making the search even more specific. Using AND in a search will find articles that are about both topics at the same time - both topics must be talked about within the article.

For example, if our P is preterm infants and our I is skin-to-skin contact, it would be helpful to search for preterm infants AND skin-to-skin. However, using what we learned about OR above, we can use OR to connect synonyms within each concept, and AND to connect the two concepts together. (preterm infants OR premature infants) AND (skin-to-skin OR kangaroo care) makes use of both operators in the same search!


Both OR and AND are called boolean operators. NOT is another boolean operator, but is risky to use and not usually recommended.

Subject Headings

Subject headings are terms that have been assigned to most articles in CINAHL and in MEDLINE, which let us know what the article is generally about. A subject heading will capture any terminology variants that relate to the topic, which makes it easier for us to find more articles. 

The newest articles in a database will not have been assigned a subject heading yet, because an indexer has not yet had the chance to process the article. Furthermore, not every concept is represented by a subject heading, especially new or obscure concepts. We still need keyword searches to find these most recent or obscure articles.

The following video shows how to find subject headings in CINAHL.

Other Search Strategies

Field Searching: CINAHL and MEDLINE allow you to search specific parts of an article (title, abstract, subject, publication name, etc.). When you search for a keyword in the title field, those results will likely be primarily about that keyword. Using field searching will normally narrow down the number of results.

Phrase Searching: Put phrases into quotation marks to keep the phrase together exactly as you type it. "Advance care planning" as a keyword phrase will only find articles that use that phrase exactly. Searching for advance care planning without quotation marks would also find the following sentence: The nurse was planning to advance the IV catheter with care. Using phrase searching will narrow down the number of results.

Wildcards/Truncation: Wildcards allows us to find multiple word endings and alternative spellings without having to type them all out. Here is a list of wildcard operators in CINAHL and MEDLINE:

* The asterisk (truncation operator) stands in place for any number of characters. It can be placed in the middle or at the end of a word

nurs*: nurse, nurses, nursing, nursery, etc.

hea*one: headphone, headstone, hearthstone, etc.

# The hash symbol stands in place for 0 or 1 characters. It can be placed in the middle or at the end of a word.

colo#r: color, colour

? The question mark stands in place for exactly 1 character. It can be used only in the middle of a word.

be?t: best, beat, beet, etc.

Proximity Searching: Proximity searching lets you find articles where two words are a within a certain distance of each other. The N# operator matches to two words that are at most # words apart, in either order. nurse* N3 role would match to nurse's role, role of the nurse, nurses play an important role, but not role that is assigned to nurses.

Sorting: Results are sorted by relevance by default, but sorting by date newest may also be useful.

Putting It All Together

Once you have come up with keywords and/or subject headings for each relevant letter of PICO (and used additional search operators where necessary), you can use this downloadable handout (as seen in the image below) to structure your search. For each letter of PICO, separate each search term by the OR operator. Join each PICO letter by the AND operator. 

Sometimes your will have two components: for example, patients with diabetes and COPD. In this case, your will be made up of two rows in the image below.

When you are ready to enter your search into CINAHL or MEDLINE, you may want to start with only two letters. P and I is often an appropriate combination to start with, and additional letters can be added later if necessary. For some questions, the C may not be a key part of the question, and may never make it into the search at all. In other questions, O may not be necessary to include when it is directly linked to other parts of the question. For example, articles that discuss the use of hip protectors (I) will usually also be about reducing hip fractures (O) - you may find it is not necessary to add the O to your search and that the results you get are specific enough already.

If your P has to do with age or sex, read the following section on the page about Limiters.


You can limit your search results by year, publication type, language, and specific journal title. These limits will help you narrow down your results.

If your P is specific to an age or sex, you can use limiters to find only results that fit your criteria. There are several different age groups that you can include or exclude. Using limiters for age and sex is much simpler than using keywords or subject headings.

Please note that the version of CINAHL in the video below has slightly different limits compared to BCIT's version of CINAHL.