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Systematic Reviews for Health: 4. Develop Search Terms - Controlled Vocabulary

A guide on how a Research Librarian can help you during a systematic review process

Develop Search Terms

The Cochrane Handbook, 4.4.4 suggests searches should comprise a combination of subject terms selected from the controlled vocabulary or thesaurus (‘exploded' where appropriate) with a wide range of free-text terms (see Step 3) in order to identify as many relevant records as possible searches.

  • If you use keywords only, you could miss articles that do not use your precise terms.
  • If you use controlled vocabulary only, you could miss articles that have not been indexed yet or have older indexing.

Step 4. Controlled Vocabulary Terms

Many major bibliographic databases can be searched using subject headings (also known as subject terms, index terms, descriptors). Subject headings are used by databases to describe the content of each article they index using a "controlled vocabulary". These subject headings differ between the databases, hence, you need to establish the controlled vocabulary terms for each database that you search.  

Examples of controlled vocabulary options for UTAS databases are:

Including subject headings is your search is useful because they provide a way of retrieving articles that may use different words to describe the same concept and because they can provide information beyond that which is simply contained in the words of the title and abstract.

NOTE!  Please note that Web of Science does not provide subject headings to control a search for a topic.

Identify Relevant Subject Headings

  • It is a good idea to carry out a simple search using a few key concepts in the different databases, to find some relevant articles and see how they were indexed using controlled vocabulary. Repeat this for a number of different articles to see what subject headings have been used and decide whether you want to use them for your own search too.
  • You can search the databases' subject heading database to find out whether index terms exist for your concepts:
    • In PubMed: search each term in the MeSH database (select MeSH Database on the PubMed homepage)
      • TIP!  It's best to use truncation as otherwise MeSH terms may not be found (e.g. search for body temperature*)
    • In Ovid databases (Medline, Embase and PsycInfo): select the tab Search Tools and enter each term in the Map Term search box
    • In CINAHL: select CINAHL Headings and search each term in the search box
  • You may like to check for existing search strategies, e.g. subject search filters (see Step 3).
  • Use text mining tool PubMed PubReMiner: a simple PubMed search reveals the most frequently used MeSH terms.

TIPS!

  • Make a note of the exact subject headings, including commas. Copy and paste is best!
  • More than one subject heading might be relevant to your topic.
  • One subject heading may combine two concepts. Add the subject heading to both concepts.
  • Sometimes a concept can only be captured by combining two separate subject headings.
  • Consider See Also / Related terms and Previous indexing
  • It is worth noting the Entry terms, Used for terms, Related terms mentioned for the relevant subject headings as they could give you ideas for alternative free-text terms for Step 3.

Example

You need to identify controlled vocabulary terms for all your concepts. This needs to be done for each database that is to be searched. You will find that the terms are different but similar for each database.

MeSH (Medical Subject Headings) is the controlled vocabulary used in Medline. This Concept Table lists relevant MeSH terms using the Ovid syntax.

Concept 1 Concept 2 Concept 3 Concept 4

Dementia

Alzheimer

Huntington

Kluver

Lewy

exp Dementia/

Animal-assisted therapy

Animal-assisted activities

Animal-assisted interventions

Animal therapy

Pet therapy

Dog therapy

Dog-assisted therapy

Canine-assisted therapy

Pet-facilitated therapy

Aquarium

Animal Assisted Therapy/

Pets/

Dogs/

Cats/

Birds/

Bonding, Human-Pet/

Animals, Domestic/

Music therapy

Music

Singing

Sing

Auditory stimulation

Music/

Music Therapy/

Acoustic Stimulation/

Singing/

Aggression

Neuropsychiatric

Apathy inventory

Cornell scale

Cohen Mansfield

BEHAVE-AD

CERAD-BRSD

Behavior

Behaviour

exp Aggression/

exp Personality Inventory/

Psychomotor Agitation/

MeSH (Medical Subject Headings) is the controlled vocabulary used in Medline. This Concept Table lists relevant MeSH terms using the PubMed syntax.

Concept 1 Concept 2 Concept 3 Concept 4

Dementia

Alzheimer

Huntington

Kluver

Lewy

Dementia [mh]*

Animal-assisted therapy

Animal-assisted activities

Animal-assisted interventions

Animal therapy

Pet therapy

Dog therapy

Dog-assisted therapy

Canine-assisted therapy

Pet-facilitated therapy

Aquarium

Animal Assisted Therapy [mh:noexp]

Pets [mh]

Dogs [mh]

Cats [mh]

Birds [mh:noexp]

Bonding, Human-Pet [mh]

Animals, Domestic [mh:noexp]

Music therapy

Music

Singing

Sing

Auditory stimulation

Music [mh]

Music Therapy [mh]

Acoustic Stimulation [mh]

Singing [mh]

Aggression

Neuropsychiatric

Apathy inventory

Cornell scale

Cohen Mansfield

BEHAVE-AD

CERAD-BRSD

Behavior

Behaviour

Aggression [mh]

Personality inventory [mh]

Psychomotor agitation [mh]

*  The MeSH term Alzheimer disease is not specifically included as it is covered by exploding the MeSH term Dementia. Alzheimer disease is a more specific term below Dementia in the MeSH tree. 

Explode / Not Explode

When you search for relevant subject headings, select the most relevant term. Examine where in the tree/hierarchy it sits. There may also be more specific terms below your term. You need to decide whether you only want to

  • search on the exact subject heading only (not explode it),
  • include all narrower/more specific terms below it in the search (explode it), or
  • pick and choose from above (broader terms) or below the term (more specific terms).

NOTE The broadest relevant subject heading for your topic should always be included.

The default of whether subject headings are exploded or not varies between the databases:

Database Default Syntax Explode Syntax Not Explode
PubMed Explode [MeSH] or [MeSH Terms] or [mh] [MeSH:NoExp] or [mh:noexp]
Ovid databases (Medline, Embase, PsycInfo) Not explode exp Term/ Term/
CINAHL Not explode (MH "Term+") (MH "Term")

For a subject heading that is the most specific/narrow term in a tree, it does not matter whether the term is exploded or not, as the same search is performed.

Need More Help?
Book a consultation with a Learning and Research Librarian or contact Librarians@utas.edu.au.