In this step, you will use the PICO(DTS) you have developed for your research question to identify the concepts you will use when searching PubMed and Embase.
What makes a concept "searchable" has to do with how and where it is represented in database records for articles. For example, is it the sort of concept that appears in the abstract or the title, which is usually what you can search in a database? Does everybody use the same term to describe this concept?
Note: You will not need a concept for each PICO(DTS) element. In general you will want to identify the minimum number of concepts necessary to represent your research question. Doing so will maximize recall in your search, which helps ensure comprehensiveness.
Use the following example to guide you in developing search concepts from your PICO(DTS).
Are there randomized controlled trials demonstrating that hand washing promotion among nurses, physicians and other health care workers in the Neonatal Intensive Care Unit (NICU) reduces the incidence of hospital acquired infections in children and adults?
PICO(DTS) Elements |
Search Concepts |
||
| Population | Nurses, physicians and other health care workers in the NICU | Concept 1 | NICU |
| Intervention | Hand washing promotion | Concept 2 | Hand washing |
| Comparison | No hand washing promotion |
No concept is needed here. |
|
| Outcome | Incidence of infections in children and adults |
A concept for infection is not listed here, |
|
| Design | Randomized controlled trials (RCTs) | Concept 3 | RCTs |
| Time | Not applicable | No concept is needed here. | |
| Setting | Not applicable | No concept is needed here. | |
This translation process identifies three search concepts from the PICO(DTS) elements: NICU, hand washing, and RCTs.
Boolean operators (named for George Boole, who invented Boolean logic) are used to combine terms and concepts when searching. AND, OR, and NOT are commonly used Boolean operators. Most databases rely on capitalization to distinguish Boolean operators from search terms.
Join your search concepts (and terms within these concepts) with the appropriate Boolean operators in preparation for searching PubMed and Embase. See the definitions and examples below for guidance on using these operators.
Use "OR" to find the union of related terms. "OR" is used to combine synonyms or related terms to develop a concept. Search results will contain at least one of the terms in the search phrase (e.g. NICU OR "neonatal intensive care unit" OR "neonatal ICU").
Use "AND" to find the intersection of terms. "AND" is used to combine two or more concepts. Search results will contain at least one term from each concept [e.g. ("hand washing" OR "hand sanitation") AND (NICU OR "neonatal intensive care unit" OR "neonatal ICU")].
It can also be helpful to write out a simpler expression, like Concept 1 AND Concept 2 AND Concept 3, as a way to show how search concepts will be combined with "AND."
Use "NOT" to exclude terms or concepts, but only in exceptional circumstances. Using "NOT" to exclude terms that retrieve "false" hits may inadvertently exclude relevant records from your search [e.g. (NOT children) will exclude records that may be about both children AND adults].