Literature Searching in Ovid MEDLINE

A controlled vocabulary is a predetermined list of terms used to describe concepts or topics in a specific database. Human indexers or automated processors use this list of terms in a consistent way to index records in the database. The controlled vocabulary may also be referred to as index terms or the thesaurus. In MEDLINE, the controlled vocabulary used is MeSH or Medical Subject Headings from the National Library of Medicine.

A controlled vocabulary assists the user in retrieving more relevant and complete results from a database search.  The subject analysis done by either human or automated indexers ensures consistency in the terminology used and therefore captures records that include synonyms, non-medical terminology, or alternate spellings of an index term.

For example, in MEDLINE: “heart attack” is indexed under “myocardial infarction”; “paediatrics” and “pediatrics” are indexed under “pediatrics”.

Ovid databases will automatically map to the correct MeSH/Medical Subject Heading even if your input in the search bar is not the correct term. For example, if you type “heart attack”, the Ovid database will map to the MeSH term “myocardial infarction”.

A scope note is the definition of the MeSH term and provides notes on the coverage of the term, as well as the year the term was put into use and any previous terminology used in the past that may/may not need to be added to the search. 

Explode/focus function refers to the handling of the subject heading by the database.  If you Explode a term, you are including all of the more specific terms listed below the subject heading in the controlled vocabulary tree.  If you focus a term, you are narrowing the results as you are requiring the subject heading to be the main point of the items retrieved.  This should be used with caution as it could result in missed items. 

Subheadings increase the specificity of your search and therefore narrow your results. Examples are “adverse effects”, “etiology” and “prognosis”. These should be used with caution as they could result in missed results.