Appendix 1 - Controlled Vocabulary Tips
**Refer to the specific database's guide for more information.
Select databases (i.e., PubMed, Ovid MEDLINE, Ovid Embase, CINAHL, APA PsycINFO, EBSCO databases) use a single authoritative term – known as a subject heading, controlled vocabulary, index term, or a thesaurus – for a given concept. The database producer "controls" the vocabulary by adding new and removing old terms. This section provides additional background and tips on how to use controlled vocabulary.
Common Controlled Vocabulary Characteristics
- Organization – Most controlled vocabulary lists or thesauri are organized both alphabetically and categorically, in a hierarchy. Since the list is usually presented in an outline format, the hierarchy is often referred to as a tree. MeSH and Emtree are the acronyms for PubMed/MEDLINE’s and Embase’s lists of controlled vocabulary respectively.
- Mapping – In select databases (PubMed, Ovid MEDLINE, Ovid Embase, CINAHL, APA PsycINFO), the default is to "automatically map" the entered concept to its associated subject heading(s) and related term(s).
- Explode – Includes the selected subject heading and all or its narrower (more specific) descendant terms to expand the search. Activation of this feature varies across databases.
- Major Topic/Major Concept/Focus – Retrieves results where the selected subject heading is considered the major topic, which narrows the search. It can be applied whether the selected subject heading is exploded or not. Activation of this feature varies across databases.
Key subject heading elements generally include:
- Scope Note (or equivalent) includes a precise definition
- Subheadings (or Descriptors) are used with the subject heading to retrieve frequently discussed aspects of the topic. Use subheadings carefully as they may reduce the number of results. For example, subheadings for diseases include diagnosis, etiology, surgery, therapy, etc. while drug subheadings include administration and dosage, adverse effects, therapeutic effects, etc.
- Entry Terms (or Used For) are the synonyms for search terms. When entered into the search box, they will automatically map to the associated subject heading. Remember to consider these terms for keyword searching.
- Year denotes when the subject heading was added to the database, which helps determine if the subject heading is applicable for the years covered by the search. If not, the searcher will need to use keywords to search.
Reviewing the subject heading’s Scope Note will help the searcher to determine whether there is a match. That said, please note the following:
- Concepts may be expressed by more than one subject heading. For example, in PubMed/Ovid MEDLINE, the concept breast cancer maps to multiple MeSH subject headings.
- Concepts may require the use of more than one subject heading, For example, in PubMed/Ovid MEDLINE, the concept breast cancer survivor requires using the Boolean operator AND to combine the MeSH heading for type of cancer (breast neoplasms) with the MeSH subject heading survivors. While the searcher notices that the MeSH subject heading cancer survivors is more specific than the MeSH subject heading survivors, the searcher opts to use survivors since relevant results before 2018 may be missed as cancer survivors was added to the PubMed/Ovid MEDLINE MeSH controlled vocabulary in 2018.
Use the database’s controlled vocabulary's look-up tools to identify correct terminology:
- PubMed – Click the MeSH Database from the PubMed home page (under the Explore icon)
- Ovid MEDLINE – Check box to "Map Term to Subject Heading" in MeSH
- Ovid EMBASE – Check box to "Map Term to Subject Heading" in Emtree
- APA PsycINFO – Check box to "Map Term to Subject Heading"
- CINAHL – Check box to "Suggest Subject Terms"
- Other EBSCO databases (i.e., Academic Search Complete, Business Source Complete, ERIC, Legal Collection, etc.) – On the database’s search page, look for a link to "Subject Terms", "Thesaurus", "Subjects", or equivalent synonym to access the database’s controlled vocabulary.
Before Selecting the Correct Controlled Vocabulary Term:
- If available, review the controlled vocabulary term’s scope note. The scope note may include the controlled vocabulary term’s definition, year/date added to the database, related terms, broader terms, and narrower terms. Examples:
- In PubMed/MEDLINE, the concept breast cancer maps to multiple controlled vocabulary terms. After reviewing the various scope notes, the most applicable controlled vocabulary term is breast neoplasms.
- In PubMed/MEDLINE, the concept survivors maps to multiple controlled vocabulary terms, including cancer survivors. Even though cancer survivors is the most appropriate controlled vocabulary term, the term’s scope note indicates it was added to MeSH in 2018.
- Explode the controlled vocabulary term to recall specific or narrower concepts under the term. To retrieve articles about cancer survivors published before 2018, it is recommended to explode the controlled vocabulary term survivors to also retrieve articles indexed to the more specific controlled vocabulary term cancer survivors.
- Search using a broader controlled vocabulary term in the tree to identify all primary articles. In Embase, even though breast cancer is a controlled vocabulary term, breast tumor is the broader controlled vocabulary term that is the counterpart to breast neoplasms in MeSH. If Embase was searched only using breast cancer, it is possible to miss relevant citations.
- Topics or concepts may be expressed as more than one controlled vocabulary term. Examples:
- mortality OR death OR survival analysis
- respiration OR respiratory system OR inhalation exposure OR respiratory tract diseases
Work backwards or use the pearl-growing technique to find the correct controlled vocabulary term(s):
Example: If you already have primary articles on the topic, locate the record for those article(s) in the selected database. Then locate the thesaurus search field to see what controlled vocabulary terms have been assigned to the article(s). Use those controlled vocabulary terms to find similar articles.
See "Pearl Growing Technique" in Conduct the Search.
If the controlled vocabulary utilizes subheadings use with caution:
Selecting the wrong or inappropriate subheadings will result in poor recall of relevant articles.
Use major concepts judiciously:
Using only major concepts may restrict the literature search too much. Use major concepts when the literature search retrieves too many database records or when the recall is high. By restricting to major concept(s), the literature search will be more precise in recalling relevant database records. Do not use when there is limited recall or no retrieval of records.
See "Balancing Recall and Precision" in Refine and Save Search.
Some searches may require the use of two controlled vocabulary terms:
When looking for a cancer or neoplasm, it may require the use of two controlled vocabulary terms: (1) the term that represents the histologic type of neoplasm and (2) the term that represents the anatomical site of the neoplasm.
Examples: In MEDLINE searching for "oral squamous cell carcinoma" requires the use of both mouth neoplasms (the neoplasm by anatomical site term and Carcinoma, Squamous Cell (the neoplasm by histologic type term). The search entry would look like this:
"Mouth Neoplasms"[Mesh] AND "Carcinoma, Squamous Cell"[Mesh]
Also See: Appendix 2 – Keyword/Natural Language Tips
(CINAHL Complete, 2020; Jankowski, 2008; Patrick & Munro, 2004; U.S. National Library of Medicine, 2019; Walker & Janes, 1999; Welch Medical Library, 2019; Wessel, 2019; Wolters Kluwer, 2019)
