Constructing Free Term Searches with MeSH (Scope Notes) – Ovid MEDLINE

Background

A major strength of Abstracting and Indexing (A&I) databases, such as Ovid MEDLINE and Embase on Ovid, is that their enormous content is indexed against a controlled vocabulary or thesaurus. As discussed in previous Focused Searches, these knowledge resources are used to systematically organize, classify and give structure to the database’s content.

However, not all records can be captured using thesaurus based searches. To remedy this situation it is good practice to search on concepts, not only expressed by their equivalent thesaurus term description,  but also using free terms. A ‘free term’ is a word or phrase that describes the thing you are searching for but is not dependent on being part of a controlled vocabulary. A free term search has the additional benefit that we can search for terms across all the database fields that make up the database record.

The question then arises how do we determine which free term words and phrases would be appropriate to use? We can of course simply add them ourselves, drawing them from our own knowledge of the subject matter. Another approach is to avail of the list of terms a thesaurus indicates that its thesaurus term covers. In Ovid MEDLINE, and more specifically the MeSH thesaurus, this information can be found in the respective MeSH term’s Scope Note as indicated below.

Clicking upon the ‘i’ icon displays the full entry for the MeSH term. The scope note describes, as the expression implies, the extent or scope of meaning associated with the term, additional notes on the term, the year of entry of the MeSH term into the thesaurus and a list of Used For terms.

These ‘Used For’ terms, as displayed in the screen shot below, are a list of term variations, singular or plural forms, alternative spellings and synonyms that the indexer watches for in the indexable medical literature. Then, due to their conceptual parity the indexer makes and marks the direct connection between these terms as used in the literature and the term in the thesaurus that, in effect, represents them. So for example, where an article talks of ‘sick headaches’ or ‘status migrainosus’ these articles will be captured by the thesaurus search Migraine Disorders/ but not necessarily by migraine*.ti,ab. or migraine*.mp.    

The purpose of this Focused Search is twofold. Firstly, to flag scope notes as a source representing a comprehensive list of free terms that due to their close semantic connection to their associated thesaurus terms can help you supplement your thesaurus based searches. Secondly, to demonstrate that it is not necessary to try and render all the ‘Used For’ terms into a free term search expression. Particularly in the case of MeSH, closer examination shows that many such used for terms are entered twice, i.e. firstly in full and then as an inverted version.  And that with truncation the overall number of term variants can be reduced. The screen shot below presents an example of how all the 35 Used For terms for Migraine Disorders/ can be condensed and rendered  into a search expression as minimalist as (migraine$ or sick headache$ or status migrainosus).mp.

The Supplemental Information for this Focused Search shows you how to systematically convert the Used For Terms for both for the MeSH term Migraine Disorders/ and its exploded equivalent exp Migraine Disorders/ using a five step process, to construct the comprehensive concept searches as indicated in lines #1 to #3 and #4 to #6 respectively.

Step 1. Prepare the List of Used For Terms
Step 2. Remove the Inversions
Step 3. Truncate the Terms
Step 4. Construct the Search Expression
Step 5. Save the Search Expression in Line Format (Optional)

Practice Suggestions

1. At the MeSH term mapping screen, in addition to selecting MeSH terms and their exploded versions, you can additionally also select an .mp. rendered version of your search term. Do this for the entry term ‘migraines’. How close is the number of these results compared to the detailed search strategy discussed in the Focus Search?
2. In the Focused Search example the term ‘migraine’ is truncated as ‘migraine$’ to capture singular and plural forms of the word. Are there any advantages to truncating the term as ‘migrain$’? How could you determine this?
3. The two search expressions (alice in wonderland syndrome).mp. and (alice adj2 wonderland syndrome).mp yield the same number of results. Are there any advantages to using the ADJn operator?

 

Search Stategy

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Reviewers

Primary: Michael Fanning

Secondary: Charlotte Viken

Review Date: 2024-07-15

Expiry Date: 2025-07-15

Original search produced by:

Ovid Training Team

References:

OvidGO! / Skills Videos
Why use Ovid databases?
Subject heading searching
Truncation of keywords
Phrase searching on Ovid

Citation:

Ovid Customer Support, Constructing Free Term Searches with MeSH (Scope Notes) – Ovid MEDLINE, OvidGO! / Focused Searches, Version: 8th May 2024. Visited: < Insert Date >.