Use of MeSH in Indexing

The MeSH vocabulary is primarily designed for use by NLM to index citations for journal articles in the MEDLINE database and to search the MEDLINE data using PubMed.  MEDLINE indexing was done by human indexers for many decades but was transitioned to automated indexing in 2022 – the algorithm currently used for indexing is a version of the Medical Text Indexer termed MTIA. More information about the transition to automation can be found in this NLM Technical Bulletin article and in these frequently asked questions about indexing for MEDLINE.

For the purposes of MEDLINE indexing, biomedical concepts may be reflected in several ways by MeSH descriptors:

• With the coordination of two descriptors, e.g., JEJUNAL DISEASES and ENTERITIS for jejunitis
• With a descriptor and a subheading, e.g., MUSCLES/INJURIES for muscle injuries
• With a “pre-coordinated” descriptor, e.g., HEAD INJURIES for head injuries

The main concepts of an article are indexed via MTIA based on several factors, including their frequency in an article’s title and abstract and in PubMed similar articles, coded rules, and, in some cases, machine learning. Automated indexing generally provides the most specific MeSH descriptor available, though a broader descriptor may be indexed based on the frequency of its occurrence. Human curators review selected sets of automatically indexed citations and may add MeSH descriptors for missed main concepts during the process of curation or make other corrections.