The key to MEDLINE is a controlled vocabulary system called the Medical Subject Headings (MeSH).
MeSH terms impose uniformity and consistency to the indexing of biomedical literature and are applied to citations when they are indexed for MEDLINE. This system offers three main advantages:
1. MeSH indexing facilitates the retrieval of relevant articles even when authors have used different words or spellings to describe the same topic.
For example:
Trisomy 21, Down's Syndrome and Down Syndrome are all possible synonyms for the same topic. The MeSH term Down Syndrome covers all of the variations - saving you from having to type them all into your search.
Krebs Cycle, Tricarboxylic Acid Cycle, and Citric Acid Cycle are all possible synonyms for the same topic. The MeSH term Citric Acid Cycle covers all of the variations - saving you from having to type them all into your search.
Lung cancer, lung tumor, lung neoplasm, and pulmonary cancer are all possible synonyms for the same topic. The MeSH term Lung Neoplasm covers all of the variations - saving you from having to type them all into your search.
2. MeSH indexing increases the discoverability of citations. If a citation has no abstract or otherwise does not effectively convey the topic(s) discussed in the article, MeSH indexing allows for discovery of this citation even by basic keyword searching.
For example:
I run a basic search for chemoembolization and hepatocellular carcinoma. I am able to find the citation below (PMID: 25376280) only thanks to the MeSH indexing. Since the term chemoembolization does not appear in the title, abstract, or any other field, prior to when this citation was indexed for MEDLINE it would be missed by my search for chemoembolization and hepatocellular carcinoma. Only because the MeSH term Therapeutic Chemoembolization has been applied can I locate this record using these search terms.
3. MeSH indexing facilitates searching of both the broad and the narrow simultaneously due to the existence of the MeSH hierarchy. MeSH Headings, Subheadings and Publication Types are organized in hierarchies, or "MeSH trees".
At the most general level of the hierarchy are very broad headings such as "Anatomy" or "Mental Disorders". More specific headings are found at narrower levels of the hierarchy, such as "Ankle" and "Conduct Disorder". A MeSH term can be part of one or more hierarchies.
For example:
Check out the MeSH entry for Cardiovascular Diseases. Scroll to the bottom to see the MeSH tree. If I am interested in smoking and cardiovascular disease then by using the term Cardiovascular Diseases in my search, I will automatically retrieve citations containing the term smoking and cardiovascular diseases as well as smoking and the over 50 more specific types of cardiovascular disease found in the hierarchy (e.g. smoking and cardiomegaly, smoking and hypertension, smoking and vasculitis, etc.)
Each year, MeSH terms are added or changed to define new trends and concepts. For example, in 2013 the terms Proton Therapy and Mitochondrial Degradation were added to MeSH, and the term Phosphoric Acid Esters was changed to Organophosphates.
Remember, only MEDLINE records are indexed with MeSH. Records in PubMed that are not in MEDLINE are NOT indexed with MeSH descriptors.
Display MeSH Vocabulary in PubMed
Display a record's MeSH descriptors by clicking the MeSH Terms link or the double arrows below the MEDLINE citation in PubMed's Abstract view.
PubMed: Comprehensive, Intuitive Searching
PubMed is the interface used most often to search MEDLINE at Mount Sinai. In addition to being free, PubMed offers several advantages over other MEDLINE search platforms (ex. OvidSP, ISI Web of Knowledge).
Automatic Term Mapping is a key feature of PubMed's search formula since this mapping enables more comprehensive search results than other search interfaces.
How Automatic Term Mapping (ATM) Works
The Automatic Term Mapping process adds subject heading words from the MeSH thesaurus to your search in all fields of every PubMed record, including those that are not indexed for MEDLINE.
First, ATM compares terms from your search query with MeSH terms, journal titles, author and investigator names. It uses a MeSH translation table to "map" your search words or phrases to MeSH headings or subheadings. If a match is found in the MeSH translation table:
Example: When you search for heart attack, PubMed maps your query to the MeSH "Myocardial Infarction".
PubMed (NOT MEDLINE) Content
PubMed provides access to MEDLINE and to other records that are not a part of the MEDLINE database.
MEDLINE citations make up the majority (approximately 80%) of the PubMed, but PubMed includes other records that are not a part of MEDLINE. Records in PubMed that are not part of MEDLINE do not contain MESH terms.
Among the PubMed records that are not part of MEDLINE are:
Records in PubMed that are not part of MEDLINE do not contain MESH terms.
Check Your Status Tags
MEDLINE records are identified with the status tag [Indexed for MEDLINE]. Note that the Status Tags are available on the Abstract view only.
It's important to be aware that PubMed does NOT search the full-text of articles. When you search in PubMed, you are searching articles' citation records (article name, abstract, journal name, author names, etc.), not the full text of the articles. This is why the MeSH indexing is so crucial for comprehensive discovery.
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