Search Strategies for Health Sciences Research

Boolean operators are a way to construct a computer searchable question. Use Boolean operators (AND, OR, NOT) to combine or exclude search terms.

Boolean Operators & Pubmed

PubMed is unique in that it does something called "Automatic Term Mapping" (or ATM). When you do a keyword search, it will automatically add synonyms and MeSH terms to your search.

This greatly expands your search, and it means that you don't always need to know the MeSH term, as PubMed will try to add the MeSH term to your search for you.

BUT...

Using truncation, quotation marks and proximity searching will turn off PubMed's automatic term mapping!

So if you are using any of these methods in your keyword search in PubMed, you might want to try a search without these methods to compare the two strategies and see how PubMed's ATM might change your search results.

While PubMed automatically maps your search terms to subject headings to get you the MOST results, CINAHL works in the reverse: it is intentionally narrow, and if you want to search subject headings, you must intentionally add them to your search.

For example, let's say you are searching for information about spinal manipulation and exercise to treat lumbar pain.

If you want research that compares spinal manipulation and exercise, you want to connect your search terms with AND: lumbar pain AND spinal manipulation AND exercise. Using AND will retrieve all three search terms, which is important if you are looking for research that compares those treatment options. 

If you want research on either spinal manipulation or exercise, you can use an OR: lumbar pain AND (spinal manipulation OR exercise). You might do this if you aren't comparing the two treatment options; rather, you want studies that include either of those types of treatment.

NOTE that I put parentheses around spinal manipulation and exercise. This is because databases read your search from left to right, like a mathematical formula. If you don't include the parenthesis, you might find information about lumbar pain and spinal manipulation... or you might just find information about exercise that has nothing to do with back pain!!

A good way to think about this is: What are your MUST-HAVE concepts? For this question, there are three: the problem (lumbar pain) and your two treatment options that you are comparing. You'll want to connect each MUST-HAVE concept with an AND. You can add alternative keywords to your search, but just make sure you are clumping together your concepts using parentheses. For example:

For this next example, you have only TWO concepts: the problem (lumbar pain) and the intervention (either exercise or spinal manipulation). You are not wanting to compare the two treatment options, but just see information about either of them -- in this case, you would nest those treatment options together with the boolean operator OR. Adding alternative keywords might look like this:

(lumbar pain OR low back pain) AND (exercise OR spinal manipulation OR "manual therapy" OR chiropractic)

Combining Keywords and Subject Headings

You can also try combining keywords and subject headings as synonyms. For example, if you were searching for ED patients, you might use the term Emergency Department. But you could also search Emergency Room. If you are searching CINAHL, the CINAHL subject heading for emergency departments is Emergency Service; for Pubmed, the MESH term is Emergency Service, Hospital.

So if you were searching CINAHL, you could search: 

MH "Emergency Service" OR "emergency room" OR "emergency department"

If you were searching Pubmed, your search could be:

"Emergency Service, Hospital"[Mesh] OR "emergency room" OR "emergency department"

You can do this for each PICOT concept you are using. Again, each PICOT concept should be connected using the Boolean Operator AND, while alternative search terms / synonyms are separated with an OR. If you are creating one long search string (rather than entering each PICOT component on a separate search line), make sure to nestle your concepts using parenthesis:

("Emergency Service, Hospital"[Mesh] OR "emergency room" OR "emergency department") AND ("Patient Compliance"[Mesh] OR adherence OR compliance)