MeSH Headings and Literature Searching

Rachel AdamsAcademic Support LibrarianThe Libraryr.adams@salford.ac.uk http://blogs.salford.ac.uk/digital-literacy-skills/

• MeSH = “Medical Subject Headings” • Created by the National Library of Medicine• A ‘controlled vocabulary’ of pre-defined terms• Covers all aspects of medicine and health care• Designed in a hierarchy of terms and phrases• Updated annually

• Used for searching databases, most notably Medline / PubMed and Cochrane Library

What is MeSH

• MeSH is not the only controlled vocabulary but it is the best known.

• Other databases use their own variations

• CINAHL uses Cinahl Headings

Controlled Vocabularies

MeSH ‘Trees’

A hierarchy of terms is arranged in ‘trees’ starting with a broad topic and branching into more specific ones:

Manually navigate the latest MeSH hierarchy:

Viewing the trees

• Search for terms at http://www.nlm.nih.gov/mesh/MBrowser.html

• Browse through the hierarchy at http://www.nlm.nih.gov/cgi/mesh/2014/MB_cgi

Viewing headings when search databases:

• Select to search using MeSH headings rather than just keywords (“map term to subject headings”)

• When the list of relevant MeSH headings appears click on the appropriate term

• You will be taken to where that term sits in the overall hierarchy.

• MeSH should provide the ‘true’ meaning of a term where a word might be used in more than 1 context.

• MeSH headings include synonyms so will search for related terms.

• MeSH will deal with the problem of homonyms (where a word can have more than 1 meaning)

• MeSH helps deal with problems arising from spelling variations or errors.

• One of the biggest benefits for many people is that MeSH can lead to finding terms not commonly used or known. You can use it like a thesaurus to identify alternative terms.

Benefits of using MeSH

• MeSH terms are best used in combination with your own key terms

• Keywords are easy to define • Keywords use natural language • Keywords can deal with new techniques MeSH hasn’t

caught up with • Takes less time to identify keywords than search for

MeSH terms • MeSH terms might not fully represent your topic

What about keywords?

Using the NLM MeSH Browser:

• “ Main Headings” (Descriptors): the MeSH terms – e.g. “diagnostic imaging”

• “ Qualifiers” (Subheadings) – aspects of a MeSH term you can select to narrow down your results.

– e.g adverse effects

• “ Supplementary Concepts” – not part of the controlled vocabulary

• Then choose which search option you want…

MeSH Terminology

Using the NLM MeSH browser

• “ Find exact term ” takes you to the entry for that term – includes a brief definition and related terms.

• “ Find terms with all fragments ” brings a list which includes all the terms in your search (useful when searching for a phrase e.g. diagnostic imaging)

• “ Find terms with any fragments ” finds any words in your search

MeSH Terminology

Using MeSH as a thesaurus in (OVID) Medline:

• From the search page, select “Search Tools” • Search for your term then select one of the following:

– Map Term : maps your term to a MeSH heading (you can then search from this point by selecting a heading).

– Tree : see a mesh term within the overall hierarchy. – Permuted Index : your term within the context of

similar or related terms. – Scope Note : information about that term, including

definitions.

Mesh Terminology

• Select the Advanced Search option. • Ensure “Map Term to Subject Heading” is ticked

– Enter keyword and search

• A list of possible MeSH terms appears – “Explode” – will find that term and any more specific terms

that sit under it within the MeSH hierarchy. – “Focus” – will search for that term but only return articles

where it considers that is the main content of the article.

• If a second screen of options appears: – “Subheadings” – a set of categories you can narrow a

MeSH term down by – only select if genuinely relevant, otherwise continue without selecting any.

Searching OVID Medline using MeSH headings

• Now you (hopefully) understand the concept of MeSH headings you need to apply it to your searches.

• To search effectively you need to create a search strategy. This may include keywords and MeSH terms.

• Start by defining your terms – Locate the key words or phrases in your question / topic. – Consider different spellings – Identify all the possible synonyms or alternatives for each

keyword – Use a MeSH thesaurus to see how these key words and

phrases might map over to subject headings.

Putting it into Practice

PICO A system you may find helpful when defining the topic – break your question down under the following headings then identify all the related terms, including MeSH headings that might also be useful in your search:

– Patient / Population / Problem e.g. elderly / older people / aged* / senior

– Intervention e.g. exercise therapy* / exercise* / physical activity / exercise movement techniques* /

– Control / Comparison e.g. drug therapy* / pain killer / anti-inflammatory

– Outcome e.g. pain reduction / pain measurement* / pain control / suffering* / patient satisfaction* / quality of life*

* Denotes MeSH heading

Putting it into Practice

• Identify key databases to search, for example: – Medline – all aspects of medical & health care – Cochrane Library – includes Cochrane Database of

Systematic Review – CINAHL – nursing and allied health literature

• Search using a combination of relevant keywords and MeSH headings – Combine with OR where you have related terms

(aged OR older OR senior OR geriatric…)

– Combine with AND where you want both topics(pain killer AND low back pain)

Putting it into Practice