Many library databases will assign a specific list of terms—CINAHL "Subject Headings," PubMed and MEDLINE "MeSH" (Medical Subject Headings), the PsycInfo "Thesaurus"—to represent an idea, instead of relying solely on the keywords or phrases different authors use in their articles. Examine these to find the best terms, and consider your topic from multiple viewpoints:
Subject headings are updated annually, but the updates may lag real-world developments. mRNA Vaccines was added to MeSH in 2022 and CINAHL does not yet offer a subject heading specifically for this concept.
When you find references to relevant articles, examine their subject indexing in a detailed view
to find additional subject terms for your search.
If the database record for the item was added recently, it may lack subject headings, but they will be added at a later date.
"Explode" in health sciences databases retrieves references containing
(selected subject term) OR (all the more specific subject headings in its "tree" hierarchy or hierarchies)
If you explode the subject heading Face, you will also retrieve articles specifically about Nose, Eyelashes, etc.
PubMed automatically explodes MeSH terms, but you must specify explodes in all most other databases.
Health sciences database indexing usually identifies which subject headings describe the primary topic of an article. Use this feature to reduce an overwhelming number of results that persist after applying all other search terms, limits, and filters.
Use subheadings to create more precise searches if applying all other search terms, limits, and filters returns overly broad results. Select all appropriate subheadings, using the MeSH Qualifiers List and scope notes for guidance.
Aspirin/administration and dosage
Aspirin/therapeutic use
While you can apply subheadings to exploded subject headings, usually they cannot be exploded themselves.
Tips:
Use keywords as well as subject headings to comprehensively search a topic.
Because citations are added to CINAHL and PubMed before they are fully indexed, a search strategy including keywords will retrieve references most recently added to the databases.